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Post-harvest studies of a radiant energy-induced disorder of tomato fruits Adegoroye, Adegoke Samuel 1980

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POST-HARVEST STUDIES OF A RADIANT ENERGY-INDUCED DISORDER OF TOMATO FRUITS by ADEGOKE SAMUEL ^ADEGOROYE . , H o n s . A g r i c , U n i v e r s i t y o f I f e , N i g e r i a , 19 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n THE FACULTY OF GRADUATE STUDIES Department o f P l a n t S c i e n c e We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o t h e r e q u i r e d s t a n d a r d THE © UNIVERSITY OF BRITISH COLUMBIA A p r i l 198 0 Adegoke Samuel A d e g o r o y e , 198 0 In presenting th i s thesis in pa r t i a l fu l f i lment of the requirements for an advanced degree at the Univers ity of B r i t i s h Columbia, I agree that the Library shal l make i t f ree ly avai lable for reference and study. I further agree that permission for extensive copying of th i s thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It i s understood that copying or publ icat ion of th i s thesis for f inanc ia l gain shal l not be allowed without my written permission. Department nf PLAhJT SO}£nJCZ The Univers ity of B r i t i s h Columbia 2075 wesbrook Place Vancouver, Canada V6T 1W5 ABSTRACT L a b o r a t o r y e x p e r i m e n t s and some f i e l d and greenhouse s t u d i e s were c a r r i e d out t o d e t e r m i n e the mode o f a c t i o n o f r a d i a n t e n e r g y i n the development o f a p o s t - h a r v e s t s u n s c a l d d i s o r d e r o f tomato ( L y c o p e r s i c o n e s c u l e n t u m M i l l c . v . V e n d o r ) f r u i t s . The e f f e c t s o f the d i s o r d e r on p o s t - h a r v e s t f r u i t q u a l i t y and p h y s i o l o g y were e v a l u a t e d by t h e p h y s i c a l d e t e r m i n a t i o n o f t e x t u r a l c h a r a c t e r i s t i c s , t h e a n a l y s i s o f some c h e m i c a l c o n s t i t u e n t s and t h e measurement o f f r u i t gas exchange. The a b i l i t y o f v a r i o u s s t o r a g e t e m p e r a t u r e s , p h o t o p e r i o d s and oxygen c o n c e n t r a t i o n s t o a l l e v i a t e i n j u r y was a l s o examined. The e f f e c t i v e n e s s o f r a d i a n t energy i n c a u s i n g s u n s c a l d i n j u r y was found t o depend on the amount o f r a d i a n t energy i n the i n f r a - r e d waveband. The a c t i o n o f i n f r a - r e d r a d i a t i o n was t h e r m a l r a t h e r t h a n p h o t o c h e m i c a l . The use o f h i g h a i r t e m p e r a t u r e s t o h e a t f r u i t s p r o d u c e d symptoms s i m i l a r t o s u n s c a l d e x c e p t t h a t t h e c o l o u r o f t h e f r u i t s u r f a c e became g r e y i s h r a t h e r t h a n w h i t e . I n j u r y can d e v e l o p a t a l l s t a g e s o f r i p e n e s s b u t symptoms v a r y w i t h stage o f r i p e n e s s . I n j u r y a l s o d e v e l o p s i n l i g h t i n t h e absence o f oxygen o r i n d a r k n e s s . P h o t o o x i d a t i o n does n o t a p p e a r t o be a p r e r e q u i s i t e f o r i n j u r y d e v e l o p m e n t . I n j u r i o u s r a d i a t i o n t r e a t m e n t s c a u s e d a l o s s o f g r e e n c o l o u r and i n j u r e d f r u i t s f a i l e d t o s y n t h e s i z e t h e r e d p i g m e n t ; l y c o p e n e , i n s t o r a g e . I n j u r y d i d n o t r e s u l t i n any a p p r e c i a b l e l o s s i n l y c o p e n e c o n t e n t once the pigment had formed. The mode o f a c t i o n o f i n t e n s e e l e c t r o m a g n e t i c r a d i a t i o n on f r u i t c o l o u r t h e r e f o r e appears t o be by d e s t r u c t i o n o f t h e mechanism o f c a r o t e n o i d s y n t h e s i s r a t h e r t h a n by i n c r e a s e d c a r o t e n o i d d e g r a d a t i o n . I n j u r y p r e v e n t e d p r o t o p e c t i n s o l u b i l i z a t i o n d u r i n g subsequent s t o r a g e . I t a l s o l e d t o a l a r g e r e d u c t i o n i n a s c o r b i c a c i d c o n t e n t and an i n c r e a s e i n p H . The changes i n a s c o r b i c a c i d c o n t e n t and pH o c c u r r e d p r o g r e s s i v e l y d u r i n g t h e development o f i n j u r y . Changes i n t h e t e x t u r a l a t t r i b u t e s o f tomato f r u i t s were a s s e s s e d by measurements o f s i x f o r c e - d e f o r m a t i o n c h a r a c t e r i s t i c s : D e f o r m a t i o n , P e r i c a r p s t r e n g t h , Mesocarp r e s i s t a n c e , C o m p l i a n c e , F i r m n e s s and T o u g h n e s s . Toughness d i d n o t s i g n i f i c a n t l y change d u r i n g r i p e n e s s . A l t h o u g h t h e e f f e c t o f i n j u r y on Mesocarp r e s i s t a n c e was n o t s i g n i f i c a n t , t h e i n t e r a c t i o n o f i n j u r y w i t h s t o r a g e was s i g n i f i c a n t f o r t h e c h a r a c t e r i s t i c . F o u r c h a r a c t e r i s t i c s : P e r i c a r p s t r e n g t h , Mesocarp r e s i s t a n c e , C o m p l i a n c e and F i r m n e s s were h i g h l y c o r r e l a t e d w i t h p r o t o p e c t i n c o n t e n t . Of t h e t e x t u r a l i n d i c e s , 2 C o m p l i a n c e was t h e b e s t p r e d i c t o r (R = 90.4%; SA = 1.97) o f p r o t o p e c t i n c o n t e n t a t d i f f e r e n t l e v e l s o f i n j u r y , i r r e s p e c t i v e o f r i p e n e s s o r s t o r a g e . I t i s t h e r e f o r e recommended t h a t C o m p l i a n c e , r a t h e r than F i r m n e s s be u s e d f o r d e t e c t i n g changes i n t h e " s o f t n e s s " o f tomato f r u i t s . - XV -" I n d u c t i o n " and " i n c i p i e n t " t y p e s o f i n j u r y a c c e l e r a t e d t h e o n s e t o f t h e r e s p i r a t o r y c l i m a c t e r i c . "Advanced" t y p e o f i n j u r y r e d u c e d r a t e s o f r e s p i r a t i o n d u r i n g f r u i t r i p e n i n g . The f a i l u r e o f i n j u r e d f r u i t s t o r i p e n n o r m a l l y was n o t due t o l a c k o f e t h y l e n e p r o d u c t i o n s i n c e r a t e s o f e t h y l e n e p r o d u c t i o n were h i g h i n i n j u r e d f r u i t s . The r e l a t i o n s h i p between t h e r e s p i r a t o r y c l i m a c t e r i c and e t h y l e n e p r o d u c t i o n was s h i f t e d by i n j u r y . S t o r a g e t r e a t m e n t s i n v o l v i n g d i f f e r e n t t e m p e r a t u r e s , p h o t o p e r i o d s and oxygen c o n c e n t r a t i o n s d i d n o t a l l e v i a t e i n j u r y . I t i s s u g g e s t e d t h a t e f f o r t s aimed a t c o n t r o l l i n g i n j u r y s h o u l d e m p h a s i z e p r e v e n t i o n o f e x p o s u r e t o r a d i a t i o n r a t h e r t h a n a t t e m p t t o c u r e i n j u r y i n e x p o s e d f r u i t . - v -TABLE OF CONTENTS Page ABSTRACT i i TABLE OF CONTENTS • • v L I S T OF TABLES x LIST OF FIGURES x i i ACKNOWLEDGEMENTS xv INTRODUCTION 1 LITERATURE REVIEW 5 P h y s i o l o g i c a l S t r e s s e s and D i s o r d e r s : Some T e r m i n o l o g y 5 E l e c t r o m a g n e t i c R a d i a t i o n . . 11 A b s o r p t i o n o f E l e c t r o m a g n e t i c R a d i a t i o n 13 I n j u r i o u s E f f e c t s o f R a d i a n t Energy 15 E f f e c t s o f U l t r a v i o l e t R a d i a t i o n 15 E f f e c t s o f V i s i b l e R a d i a t i o n 16 P r e - h a r v e s t e f f e c t s 16 P o s t - h a r v e s t e f f e c t s 18 E f f e c t s o f I n f r a r e d R a d i a t i o n . 18 B i o p h y s i c a l and C h e m i c a l B a s i s f o r H i g h T e m p e r a t u r e E f f e c t s 21 I n j u r i o u s E f f e c t s o f H i g h T e m p e r a t u r e s 23 P r e - h a r v e s t e f f e c t s . 2 4 P o s t - h a r v e s t e f f e c t s 25 S u n s c a l d 26 - v i -Q u a l i t y Changes i n Tomato F r u i t s D u r i n g R i p e n i n g 30 C o n c e p t s o f r i p e n i n g 30 C o l o u r . 3 1 T e x t u r e 34 Enzyme a c t i v i t y i n r e l a t i o n t o f i r m n e s s d u r i n g tomato r i p e n i n g 3 5 C h e m i c a l c o n s t i t u e n t s 38 The c l i m a c t e r i c , e t h y l e n e p r o d u c t i o n and t h e i r r e l a t i o n s h i p t o r i p e n i n g i n tomato f r u i t s .40 E t h y l e n e P r o d u c t i o n Under S t r e s s C o n d i t i o n s 43 MATERIALS AND METHODS 4 5 P l a n t M a t e r i a l : H a r v e s t i n g and P r e - t r e a t m e n t H a n d l i n g 45 T r e a t m e n t Chamber D e s i g n and C o n s t r u c t i o n 45 Measurement and c o n t r o l o f i r r a d i a n c e 4 9 Measurement and c o n t r o l o f t e m p e r a t u r e 5 0 V i s u a l R a t i n g Schemes 51 ( i) R i p e n e s s 51 ( i i ) I n j u r y . 5 3 C h a r a c t e r i z a t i o n o f C a u s a l F a c t o r s 53 E n v i r o n m e n t and d u r a t i o n o f e x p o s u r e 53 R a d i a t i o n t y p e s 55 Waveband e f f e c t s 56 H i g h t e m p e r a t u r e s 57 Oxygen c o n c e n t r a t i o n • • 60 - v i i -C h a r a c t e r i z a t i o n o f F r u i t Responses t o I n j u r y .62 T r e a t m e n t S t a n d a r d i z a t i o n 62 Measurement o f P h y s i c a l C h a r a c t e r i s t i c s 62 I n f r a r e d a b s o r p t i o n s p e c t r a 62 F o r c e - d e f o r m a t i o n c h a r a c t e r i s t i c s 63 Measurement o f Some C h e m i c a l C h a r a c t e r i s t i c s . . . . 70 P r o t o p e c t i n 7 0 A s c o r b i c a c i d 71 pH 71 Lycopene . .71 Measurement o f F r u i t Gas Exchange and Water L o s s . . 72 C a r b o n D i o x i d e 72 E t h y l e n e . 7 3 M o i s t u r e Loss. 74 C o n t r o l o f I n j u r y 74 Data A n a l y s i s . 75 RESULTS 76 E f f e c t o f E n v i r o n m e n t and T r e a t m e n t D u r a t i o n on I n j u r y Development 7 6 I n i t i a l E v a l u a t i o n o f t h e E f f e c t s o f D i f f e r e n t R a d i a t i o n and T e m p e r a t u r e T r e a t m e n t s on I n j u r y Development . . , ' 7 9 E f f e c t o f D i f f e r e n t Wavebands on I n j u r y Development . . 85 E f f e c t o f T e m p e r a t u r e T r e a t m e n t s A p p l i e d i n D a r k n e s s . .89 E f f e c t o f 0 2 C o n c e n t r a t i o n D u r i n g R a d i a t i o n Treatment, .92 Changes i n F o r c e - D e f o r m a t i o n C h a r a c t e r i s t i c s o f Tomato F r u i t s 92 - v i i i -E f f e c t s o f f r u i t p o s i t i o n on f o r c e - d e f o r m a t i o n c h a r a c t e r i s t i c s .95 E f f e c t s o f main f a c t o r s : r i p e n e s s , i n j u r y and s t o r a g e on f o r c e - d e f o r m a t i o n c h a r a c t e r i s t i c s . . . . 100 E f f e c t s o f i n j u r y a t d i f f e r e n t s t a g e s o f r i p e n e s s on f o r c e - d e f o r m a t i o n c h a r a c t e r i s t i c s . . . 100 E f f e c t s o f s t o r a g e and i n j u r y on f o r c e -d e f o r m a t i o n c h a r a c t e r i s t i c s 104 E f f e c t s o f R i p e n e s s , I n j u r y and S t o r a g e on Some C h e m i c a l C h a r a c t e r i s t i c s 106 E f f e c t s o f r i p e n e s s on p r o t o p e c t i n , a s c o r b i c a c i d and pH 106 E f f e c t s o f i n j u r y on p r o t o p e c t i n , a s c o r b i c a c i d and p H . . . . . . . . . . . . 109 E f f e c t s o f d i f f e r e n t l e v e l s o f i n j u r y a t v a r i o u s s t a g e s o f r i p e n e s s 109 E f f e c t s o f s t o r a g e and i n j u r y on p r o t o p e c t i n , a s c o r b i c a c i d and pH 112 E f f e c t s o f i n j u r y a t d i f f e r e n t s t a g e s o f r i p e n e s s on t h e u l t i m a t e l y c o p e n e c o n t e n t o f tomato 117 P o s t - H a r v e s t R a t e s o f R e s p i r a t i o n , E t h y l e n e P r o d u c t i o n and M o i s t u r e L o s s o f Tomato F r u i t s I n j u r e d by D i r e c t E x p o s u r e s t o R a d i a n t E n e r g y . . . . . 121 Rate o f r e s p i r a t i o n 121 Rate o f e t h y l e n e p r o d u c t i o n 124 M o i s t u r e l o s s 126 C o n t r o l o f I n j u r y 129 DISCUSSION 132 C h a r a c t e r i z a t i o n o f F a c t o r s C a u s i n g I n j u r y . . . . . . . . 132 I n f r a r e d r a d i a t i o n 133 H i g h t e m p e r a t u r e s 138 P o s s i b l e mechanisms o f i n j u r y development 145 i x -Changes i n F o r c e - D e f o r m a t i o n C h a r a c t e r i s t i c s 148 E f f e c t s o f r i p e n e s s 1 4 8 E f f e c t s o f s t o r a g e 149 E f f e c t s o f f r u i t p o s i t i o n 150 E f f e c t s o f f r u i t i n j u r y 1 5 1 E f f e c t s o f s t o r a g e on f o r c e - d e f o r m a t i o n c h a r a c t e r i s t i c s o f i n j u r e d f r u i t s 153 E f f e c t s o f R i p e n e s s , I n j u r y and S t o r a g e on P r o t o p e c t i n l ^ 4 E f f e c t s o f R i p e n e s s , S t o r a g e and I n j u r y on A s c o r b i c A c i d C o n t e n t 160 E f f e c t s o f R i p e n e s s , S t o r a g e and I n j u r y on pH 161 Gas Exchange 1 6 4 C o n t r o l o f I n j u r y 168 SUMMARY AND CONCLUSIONS I" 7 0 LITERATURE CITED i 7 4 L I S T OF TABLES A V i s u a l R a t i n g Scheme f o r A s s e s s i n g t h e R i p e n e s s o f Tomato F r u i t s . A V i s u a l R a t i n g Scheme f o r I n j u r y A s s e s s m e n t i n R a d i a n t Energy T r e a t e d D e t a c h e d Tomato F r u i t s D i m e n s i o n a l A n a l y s i s o f t h e F o r c e - D e f o r m a t i o n Curve o f Tomato F r u i t s , O b t a i n e d From P u n c t u r e T e s t s U s i n g t h e I n s t r o n T e s t i n g Machine E f f e c t s o f F r u i t s S i z e on t h e D e t e r m i n a t i o n o f F o r c e - D e f o r m a t i o n C h a r a c t e r i s t i c s o f Tomato F r u i t s by t h e I n s t r o n T e s t i n g Machine U s i n g a M o d i f i e d P u n c t u r e Probe 1 mm D i a m e t e r T i p , E f f e c t s o f E n v i r o n m e n t and T r e a t m e n t D u r a t i o n on I n j u r y Development , R e l a t i v e E f f e c t i v e n e s s o f D i f f e r e n t R a d i a t i o n T r e a t m e n t s i n C a u s i n g T e m p e r a t u r e Changes. . E f f e c t s o f D i f f e r e n t • W a v e b a n d s on I n j u r y Development i n D e t a c h e d Tomato F r u i t s a t 50 C A i r T e m p e r a t u r e E f f e c t s o f R a d i a t i o n T r e a t m e n t on t h e Speed o f I n j u r y Development i n D e t a c h e d Tomato F r u i t s a t 40°C A i r T e m p e r a t u r e s E f f e c t s o f T e m p e r a t u r e A p p l i e d i n Darkness on I n j u r y Development. I n j u r y Development on D e t a c h e d Tomato F r u i t s Exposed t o V a r y i n g C o m b i n a t i o n o f I r r a d i a n c e and T e m p e r a t u r e f o r V a r y i n g T r e a t m e n t D u r a t i o n - x i -T a b l e ' E^2£ 11 E f f e c t s o f Oxygen C o n c e n t r a t i o n D u r i n g T r e a t m e n t on t h e Development of I n j u r y i n M a t u r e - G r e e n Tomato F r u i t s 93 12 F V a l u e s and t h e S i g n i f i c a n c e o f M a i n E f f e c t s and I n t e r a c t i o n s on F o r c e - D e f o r m a t i o n C h a r a c t e r i s t i c s 96 13 E f f e c t s o f F r u i t P o s i t i o n on F o r c e - D e f o r m a t i o n C h a r a c t e r i s t i c s 98 14 An Example o f t h e A n a l y s i s o f V a r i a n c e f o r F o r c e - D e f o r m a t i o n C h a r a c t e r i s t i c s D e t e r m i n a t i o n t o I n d i c a t e t h e Complete P a r t i t i o n o f V a r i a t i o n i n t h e A n a l y s i s : A n a l y s i s o f V a r i a n c e f o r F i r m n e s s 99 15 E f f e c t s o f M a i n F a c t o r s : R i p e n e s s , I n j u r y and S t o r a g e on F o r c e -D e f o r m a t i o n C h a r a c t e r i s t i c s 101 16 F V a l u e s and S i g n i f i c a n c e o f M a i n E f f e c t s and on P r o t o p e c t i n , A s c o r b i c A c i d and pH 107 17 E f f e c t s o f S t o r a g e T r e a t m e n t s on A l l e v i a t i o n o f I n j u r y i n Tomato F r u i t s I n j u r e d by R a d i a n t E n e r g y : (a) E f f e c t s o f d a r k n e s s , l i g h t and d u r i n g ' s t o r a g e on 0^ t r e a t m e n t s on a l l e v i a t i o n o f i n j u r y 130 (b) E f f e c t s o f p a r t i a l o r t o t a l b l a c k p l a s t i c w r a p p i n g o f i n j u r e d tomato f r u i t s d u r i n g s t o r a g e e x p o s u r e t o l i g h t and C)^' o n i n j u r y 131 18 C o r r e l a t i o n C o e f f i c i e n t s R e l a t i n g P r o t o p e c t i n w i t h F o r c e - D e f o r m a t i o n C h a r a c t e r i s t i c s 157 19 C o r r e l a t i o n C o e f f i c i e n t s R e l a t i n g C o m p l i a n c e w i t h O t h e r F o r c e -D e f o r m a t i o n C h a r a c t e r i s t i c s 159 - x i i -L I S T OF FIGURES F i g u r e Page 1 T r e a t m e n t Chambers . . . . 4 6 2 S p e c t r a l Energy D i s t r i b u t i o n o f U n f i l t e r e d R a d i a t i o n from 300 Watts PAR 56/2 MFL Medium F l o o d , C o o l Lux I n c a n d e s c e n t S y l v a n i a Lamps (LUR) and t h e sun (SR): E f f e c t s o f 2.5 cm deep W a t e r - b a t h and CBS 750 F a r - r e d F i l t e r on the S p e c t r a l Energy D i s t r i b u t i o n o f t h e R a d i a t i o n From S y l v a n i a Lamps. . . . 5 8 3 S c h e m a t i c Drawing o f t h e C l o s e d Gas Exchange System Used t o Measure CO~ Exchange P a t t e r n s o f Tomato F r u i t s a t D i f f e r e n t 0 2 C o n c e n t r a t i o n s , D u r i n g E x p o s u r e to R a d i a n t E n e r g y 61 4 I n s t r o n T e s t i n g Machine Showing t h e P u n c t u r e Probe A t t a c h m e n t Used i n the Measurement o f F o r c e - D e f o r m a t i o n C h a r a c t e r i s t i c s . . . .64 5 F r u i t P o s i t i o n D e m a r c a t i o n f o r P u n c t u r e T e s t s : The " S t y l a r " , " E q u a t o r i a l " and " C a l y x " R e g i o n s 66 6 T y p i c a l F o r c e - D e f o r m a t i o n Curve O b t a i n e d D u r i n g P u n c t u r e T e s t s Showing How F o r c e - D e f o r m a t i o n C h a r a c t e r i s t i c s Were D e t e r m i n e d 67 « 7 E f f e c t i v e n e s s o f D i f f e r e n t S o u r c e s o f R a d i a t i o n i n C a u s i n g I n j u r y on D e t a c h e d Tomato F r u i t s a t 4 0°C A i r T e m p e r a t u r e 8 0 8a F r u i t S u r f a c e T e m p e r a t u r e s D u r i n g E x p o s u r e t o ; U n f i l t e r e d R a d i a t i o n from 3 00 Watts S y l v a n i a Lamps; W a t e r - b a t h F i l t e r e d R a d i a t i o n from 30 0 Watts S y l v a n i a Lamps; R a d i a t i o n from a H e a t i n g E l e m e n t ; Heat from Hot W a t e r - b a t h 8 2 - x i i i -F i g u r e Page 8b F r u i t T e m p e r a t u r e s a t V a r i o u s Depths D u r i n g E x p o s u r e t o U n f i l t e r e d R a d i a t i o n from 300 Watts S y l v a n i a Lamps 8 2 9 E f f e c t o f O™ C o n c e n t r a t i o n on t h e Rate o f R e s p i r a t i o n o f D e t a c h e d Tomato F r u i t s D u r i n g E x p o s u r e t o 640 W m - 2 U n f i l t e r e d R a d i a n t Energy from 300 Watts PAR 5 6/2 MFL Medium F l o o d , C o o l Lux I n c a n d e s c e n t S y l v a n i a Lamps 94 10 E f f e c t s o f I n j u r y a t D i f f e r e n t Stages o f R i p e n e s s on F o r c e -D e f o r m a t i o n C h a r a c t e r i s t i c s 102 11 E f f e c t s o f S t o r a g e and I n j u r y on F o r c e - D e f o r m a t i o n C h a r a c t e r i s t i c s 105 12 E f f e c t s o f P r e - h a r v e s t R i p e n e s s on P r o t o p e c t i n , A s c o r b i c A c i d and pH 108 13 E f f e c t s o f I n j u r y on P r o t o p e c t i n , A s c o r b i c A c i d and pH .110 14a E f f e c t s o f I n j u r y a t D i f f e r e n t Stages o f R i p e n e s s on P r o t o p e c t i n C o n t e n t - H I 14b E f f e c t s o f I n j u r y a t D i f f e r e n t Stages o f R i p e n e s s on A s c o r b i c A c i d C o n t e n t 113 14c E f f e c t s o f I n j u r y a t D i f f e r e n t Stages o f R i p e n e s s on pH 114 15a E f f e c t o f S t o r a g e and I n j u r y on P r o t o p e c t i n C o n t e n t 115 15b E f f e c t o f S t o r a g e and I n j u r y on A s c o r b i c A c i d C o n t e n t 116 15c E f f e c t o f S t o r a g e and I n j u r y on pH 118 x i v -F i g u r e Page 16 Lycopene C o n t e n t o f V i n e - r i p e Tomato F r u i t s a t V a r i o u s S t a g e s o f R i p e n e s s 119 17 E f f e c t . o f I n j u r y a t D i f f e r e n t S t a g e s o f R i p e n e s s on t h e U l t i m a t e Lycopene C o n t e n t 120 18 P h o t o g r a p h s o f Tomato F r u i t s w i t h t h e " I n d u c t i o n " , " I n c i p i e n t " , and "Advanced" Types o f I n j u r y 8 Days F o l l o w i n g T r e a t m e n t 122 19 P o s t - t r e a t m e n t Rate o f R e s p i r a t i o n o f D e t a c h e d Tomato F r u i t s a t V a r i o u s Stages o f I n j u r y 123 20 P o s t - t r e a t m e n t Rate o f E t h y l e n e P r o d u c t i o n o f Detached Tomato F r u i t s a t V a r i o u s Stages o f I n j u r y . . . . 125 21 R e l a t i o n s h i p Between t h e R e s p i r a t o r y C l i m a c t e r i c and t h e Rate o f E t h y l e n e P r o d u c t i o n i n Tomato F r u i t s a t D i f f e r e n t Stages of I n j u r y 127 22 P o s t - t r e a t m e n t M o i s t u r e L o s s o f D e t a c h e d Tomato F r u i t s a t V a r i o u s S t a g e s o f I n j u r y 128 23 P h o t o g r a p h o f a Tomato F r u i t a t t h e P i n k - r e d Stage o f R i p e n e s s , I r r a d i a t e d w i t h a 600 W m ~ 2 U n f i l t e r e d R a d i a t i o n From I n c a n d e s c e n t S y l v a n i a Lamps a t 40°C f o r 5 H o u r s ' . 137 24a Near I n f r a r e d A b s o r p t i o n S p e c t r a o f F r e e z e - d r i e d Tomato F r u i t T i s s u e i n C h l o r o f o r m (700-2500 nm) . 139 24b I n f r a r e d A b s o r p t i o n S p e c t r a o f F r e e z e - d r i e d T i s s u e i n C a r b o n T e t r a c h l o r i d e (2.5-14 um) . .140 2 5 P h o t o g r a p h s o f Tomato F r u i t s a t t h e Red S t a g e o f R i p e n e s s Showing "Foaming" and " P e r i c a r p R u p t u r e " R e s u l t i n g From E x p o s u r e t o I n t e n s e E l e c t r o m a g n e t i c R a d i a t i o n 147 - X V -ACKNOWLEDGEMENTS I w i s h t o e x p r e s s my s i n c e r e g r a t i t u d e and deep a p p r e c i a t i o n t o my r e s e a r c h s u p e r v i s o r , D r . P . A . J o l l i f f e , f o r h i s g u i d a n c e and c o n s t r u c t i v e c r i t i c i s m t h r o u g h o u t t h e c o u r s e o f t h i s s t u d y . H i s w h o l e - h e a r t e d s u p p o r t and encouragement i n t i m e s o f f r u s t r a t i o n p r o v i d e d a s t i m u l u s t h a t l e d t o t h e c o m p l e t i o n o f t h i s t h e s i s . I am a l s o g r a t e f u l t o D r . V . C . R u n e c k l e s , P r o f e s s o r and C h a i r m a n , Department o f P l a n t S c i e n c e , D r . N . R . B u l l e y , A s s o c i a t e P r o f e s s o r , Department o f B i o - R e s o u r c e E n g i n e e r i n g , and D r . S. N a k a i , P r o f e s s o r , Department o f Food S c i e n c e , f o r s e r v i n g as members o f my g r a d u a t e committee and f o r c a r e f u l l y r e v i e w i n g t h i s t h e s i s . I r e g r e t t h e l o s s o f D r . C A . H o r n b y , L a t e A s s o c i a t e P r o f e s s o r o f H o r t i c u l t u r e and a f o r m e r member o f my c o m m i t t e e , f o r h i s i n t e r e s t and l o v e . My s p e c i a l t h a n k s go t o t h e f o l l o w i n g p e o p l e : D r . G.W. E a t o n , f o r l o n g h o u r s o f d i s c u s s i o n and a s s i s t a n c e w i t h the s t a t i s t i c a l a n a l y s i s o f d a t a ; D r . M a r v i n T u n g , f o r t h e d e t e r m i n a t i o n o f f r u i t t e x t u r a l c h a r a c t e r i s t i c s ; D r . C u r t i s Welborn o f t h e C h e m i s t r y Department and D r . J o h n A r n a s o n f o r m e r l y o f t h e Department o f B o t a n y , f o r the use o f f a c i l i t i e s i n t h e i r r e s p e c t i v e l a b o r a t o r i e s ; My c o l l e a g u e s and f r i e n d s b o t h i n and out o f t h e D e p a r t m e n t , f o r p r o v i d i n g a c o n g e n i a l a t m o s p h e r e . - x v i -I am g r a t e f u l t o t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a f o r p r o v i d i n g g r a n t s towards t h i s p r o j e c t and t o my s p o n s o r , The U n i v e r s i t y o f I f e , N i g e r i a , f o r my f i n a n c i a l s u p p o r t t h r o u g h o u t t h e d u r a t i o n o f t h i s p r o j e c t . L a s t l y , I would l i k e t o thank my f a m i l y i n N i g e r i a f o r t h e i r l o v e and p a t i e n c e and God f o r H i s p r o t e c t i o n . - 1 -INTRODUCTION The tomato ( L y c o p e r s i c o n e s c u l e n t u m M i l l . ) o r i g i n a t e d i n the P e r u - E c u a d o r r e g i o n o f South A m e r i c a . A l t h o u g h i t c a n n o t be c l a s s i f i e d s t r i c t l y as a t r o p i c a l o r s e m i - t r o p i c a l c r o p ( B a i l e y 1925) t h e r e i s g e n e r a l agreement t h a t i t i s a " w a r m t h - l o v i n g " c r o p . As a d i e t a r y v e g e t a b l e , t h e tomato has e s t a b l i s h e d i t s e l f i n v a r i o u s c u l i n a r y u s e s as a f a v o u r e d component o f human f o o d s u p p l y . A c c o r d i n g t o S t e v e n s (1974) tomato r a n k s 16th i n r e l a t i v e c o n c e n t r a t i o n o f a group o f t e n v i t a m i n s and m i n e r a l s among f r u i t s and v e g e t a b l e s i n t h e U n i t e d S t a t e s . But because i t i s so h e a v i l y consumed, i t a c t u a l l y s t a n d s f i r s t i n t o t a l c o n t r i b u t i o n o f t h o s e n u t r i e n t s t o t h e U . S . d i e t . The i m p o r t a n c e o f t h e tomato i s f u r t h e r e v i d e n t i n the e x t e n t o f i t s f i e l d and g l a s s h o u s e c u l t i v a t i o n t h r o u g h o u t t h e w o r l d . Crop q u a l i t y and economic c o n s i d e r a t i o n s , however, have t e n d e d t o c o n c e n t r a t e p r o d u c t i o n i n t h e h o t t r o p i c s and s u b - t r o p i c s . Warm t e m p e r a t u r e s , i n a d d i t i o n t o p e s t and d i s e a s e p r o b l e m s w h i c h a r e e s p e c i a l l y s e v e r e i n t h o s e r e g i o n s , make i t i m p o r t a n t t h a t a p p r o p r i a t e h a r v e s t and p o s t - h a r v e s t h a n d l i n g methods a r e u s e d . Tomato f r u i t s a r e h a r v e s t e d a t v a r i o u s s t a g e s o f r i p e n e s s r a n g i n g from mature g r e e n t o f i r m - r e d ; t h e e a r l i e r s t a g e s o f r i p e n e s s a r e chosen when t h e f r u i t s a r e d e s t i n e d f o r l o n g d i s t a n c e t r a n s p o r t o r f o r l o n g term s t o r a g e . F r e s h market - 2 -tomatoes a r e a l m o s t e x c l u s i v e l y h a n d - h a r v e s t e d . .^This r e q u i r e s l o n g h o u r s o f p i c k i n g i n t h e f i e l d , w h i c h may r e s u l t i n a d e l a y between h a r v e s t and s t o r a g e . In t h e t r o p i c s , when h a r v e s t i n g i s done on h o t sunny d a y s , h a r v e s t e d f r u i t s l e f t exposed t o d i r e c t s o l a r r a d i a t i o n f o r s e v e r a l h o u r s o f t e n d e v e l o p a syndrome v a r i o u s l y termed " s u n - s c o r c h i n g " , " s u n s c a l d " o r " s u n b u r n " ( R e t i g and Kedar 1967). " S u n - s c o r c h i n g " i n v o l v e s a c h a r a c t e r i s t i c permanent b l e m i s h w h i c h can c o n s t i t u t e an i m p o r t a n t market l o s s i n r e g i o n s where modern methods o f p o s t - h a r v e s t h a n d l i n g a r e n o t p r a c t i s e d . Depending on t h e stage o f r i p e n e s s , t h e p a r t i c u l a r d i s o r d e r a p p e a r s as a w e l l - d e f i n e d t r a n s p a r e n t a n d / o r b l e a c h e d a r e a on the tomato s u r f a c e . The s u r f a c e changes unmask a r e t i c u l a t e p a t t e r n o f s u b - d e r m a l components. In extreme i n s t a n c e s the subdermal r e g i o n s become t u r b i d and s k i n r u p t u r e may o c c u r , e s p e c i a l l y i n r e d f r u i t s . S o l a r r a d i a t i o n has a l s o been i m p l i c a t e d i n a number o f o t h e r tomato d i s o r d e r s i n c l u d i n g " b l o t c h y r i p e n i n g " , " g r e e n s h o u l d e r s " and " g r a y w a l l " ( V e n t e r 1965, L i p t o n 1970b). I t i s i m p o r t a n t t o d i s t i n g u i s h p o s t - h a r v e s t s u n s c a l d from t h e above d i s o r d e r s w h i c h f e a t u r e p a t c h e s o f i r r e g u l a r r i p e n i n g ( S a d i k and Minges 196 5) and w h i c h o c c u r d u r i n g growth and d e v e l o p m e n t . F o r example, o t h e r f a c t o r s , s u c h as n u t r i e n t l e v e l s ( e s p e c i a l l y p o t a s s i u m , n i t r o g e n , b o r o n ) a n d even t h e tomato m o s a i c v i r u s (Winsor and Long 1967, Ozbun e t a l . 1967, McKeen 1972) have - 3 -a l s o been shown t o c o n t r i b u t e t o b l o t c h y r i p e n i n g . S t u d i e s on t h e r o l e o f s o l a r r a d i a t i o n i n s u n s c a l d have g e n e r a l l y a t t r i b u t e d s u n s c a l d t o " h i g h l i g h t i n t e n s i t y " ( L e v i t t 1972). L i p t o n (1970) s u g g e s t e d t h a t a s i m i l a r syndrome, w h i c h he c a l l e d " S o l a r y e l l o w i n g " , was c a u s e d by " i n f r a - r e d and s h o r t wave" r a d i a t i o n . Most p r e v i o u s s t u d i e s were c a r r i e d out on a t t a c h e d tomato f r u i t s and d i d n o t i n v o l v e t h e a p p l i c a t i o n o f t h e s p e c i f i c wavebands o f r a d i a t i o n t h o u g h t t o cause the s u n s c a l d syndrome. F u r t h e r m o r e , p r e v i o u s s t u d i e s have n o t c o n s i d e r e d f r u i t q u a l i t y changes o r g e n e r a l p o s t - h a r v e s t p h y s i o l o g i c a l changes f o l l o w i n g e x p o s u r e s t o r a d i a n t e n e r g y o f s u f f i c i e n t magnitude t o cause t h e d i s o r d e r . Such a s t u d y would be o f h e l p i n u n d e r s t a n d i n g the n a t u r e o f t h e d i s o r d e r . A l s o an u n d e r s t a n d i n g o f t h e s p e c i f i c f a c t o r s c a u s i n g and c o n t r o l l i n g t h e d i s o r d e r i s i m p o r t a n t i n any programme aimed a t a l l e v i a t i n g i t . The p r i m a r y o b j e c t i v e s o f the p r e s e n t s t u d y were: (1) t o g e n e r a t e t h e p o s t - h a r v e s t s u n s c a l d syndrome i n t h e l a b o r a t o r y and t o e v a l u a t e t h e r o l e o f r a d i a n t e n e r g y i n c a u s i n g the d i s o r d e r ; (2) t o f i n d out t h r o u g h p h y s i c a l measurements o f f r u i t t e x t u r e , how p o r t i o n s o f t h e f r u i t a r e a f f e c t e d by t h e d i s o r d e r and t o i d e n t i f y t e x t u r a l c h a r a c t e r i s t i c s w h i c h can s e r v e as u s e f u l i n d i c e s o f f r u i t r e s p o n s e t o s u n s c a l d i n j u r y ; (3) t o seek a p h y s i o l o g i c a l b a s i s t o a c c o u n t f o r t h e d i s o r d e r t h r o u g h measurements o f some c h e m i c a l c o n s t i t u e n t s and by s t u d i e s o f p r o c e s s e s o f f r u i t gas e x c h a n g e , and - 4 -(4) t o e x p l o r e ways o f c o n t r o l l i n g t h e d i s -o r d e r . - 5 -LITERATURE REVIEVJ P h y s i o l o g i c a l S t r e s s e s and D i s o r d e r s ; Some T e r m i n o l o g y S i n c e t h i s t h e s i s i s c o n c e r n e d w i t h t h e mode o f a c t i o n and h a r m f u l e f f e c t s o f i n t e n s e e l e c t r o m a g n e t i c r a d i a t i o n on tomato f r u i t s , i t w i l l be u s e f u l t o b e g i n w i t h a b r i e f r e v i e w o f some r e l e v a n t t e r m i n o l o g y . By a n a l o g y w i t h e x p r e s s i o n s commonly u s e d i n e n g i n e e r i n g L e v i t t (1972) has p r o p o s e d t h e f o l l o w i n g n o m e n c l a t u r e . A s t r e s s , i n a b i o l o g i c a l s e n s e , can be d e f i n e d as an e n v i r o n m e n t a l c o n d i t i o n c a p a b l e o f i n d u c i n g a p o t e n t i a l l y i n j u r i o u s s t r a i n i n l i v i n g o r g a n i s m s . Many d i f f e r e n t e n v i r o n m e n t a l f a c t o r s can be s t r e s s e s , i n c l u d i n g : e x c e s s r a d i a t i o n , a d v e r s e t e m p e r a t u r e s , w a t e r - d e f i c i t s , h i g h c o n c e n t r a t i o n s o f s a l t o r a i r p o l l u t a n t s , and p e s t s and d i s e a s e s . S t r a i n s p r o d u c e d i n r e s p o n s e t o s t r e s s e s may be p h y s i c a l o r c h e m i c a l i n t h e i r b a s i s . M i l d s t r e s s e s may i n d u c e o n l y e l a s t i c ( r e v e r s i b l e ) s t r a i n s , such as t h e e f f e c t s o f water d e f i c i t s above t h e permanent w i l t i n g p o i n t , and a p l a n t ' s c o n d i t i o n may r e t u r n t o n o r m a l a f t e r t h e s t r e s s i s removed. On t h e o t h e r h a n d , p l a s t i c ( n o n - r e v e r s i b l e ) s t r a i n s a r e t h e r e s u l t o f s t r e s s e s s u f f i c i e n t l y s e v e r e t o i n v o l v e s u s t a i n e d i n j u r y o r d e a t h o f t h e o r g a n i s m . A d i s o r d e r i s a permanent b l e m i s h o r i n j u r y p r o d u c e d by the e f f e c t s o f p h y s i c a l , c h e m i c a l o r b i o l o g i c a l e n v i r o n m e n t a l f a c t o r s . Hence, a d i s o r d e r i s a p l a s t i c s t r a i n . C o n t i n u i n g t h e a n a l o g y w i t h e n g i n e e r i n g t e r m i n o l o g y , an o r g a n i s m ' s a b i l i t y - 6 -t o p r e v e n t e l a s t i c o r p l a s t i c s t r a i n can be termed e l a s t i c r e s i s t a n c e o r p l a s t i c r e s i s t a n c e r e s p e c t i v e l y . The magnitude o f b i o l o g i c a l s t r a i n s depends on b o t h t h e d u r a t i o n o f e x p o s u r e t o t h e s t r e s s c o n d i t i o n and t h e i n t e n s i t y o f t h e s t r e s s f a c t o r . A l t h o u g h t h e use o f e n g i n e e r i n g - b a s e d t e r m i n o l o g y may n o t be c o m p l e t e l y a p p l i c a b l e t o b i o l o g i c a l s i t u a t i o n s , t h e above n o m e n c l a t u r e i s s u f f i c i e n t l y a p p r o p r i a t e t o j u s t i f y w i d e s p r e a d u s e , e s p e c i a l l y i n t h e case o f b i o l o g i c a l p l a s t i c s t r a i n s . P o s t - h a r v e s t p h y s i o l o g i c a l d i s o r d e r s a r e a b n o r m a l i t i e s w h i c h a r e n o t due t o d i s e a s e - c a u s i n g o r g a n i s m s and w h i c h a r e d e t e c t e d on c r o p c o m m o d i t i e s a f t e r h a r v e s t . Such d i s o r d e r s may a p p e a r as d e l e t e r i o u s changes i n e x t e r n a l o r i n t e r n a l c h a r a c t e r i s t i c s such a s : f a i l u r e t o r i p e n , abnormal c o l o u r , f l a v o u r and t e x t u r a l changes d u r i n g r i p e n i n g ; t h e development o f t i s s u e b r o w n i n g , o r t h e f o r m a t i o n o f c h l o r o t i c o r n e c r o t i c t i s s u e s . Such e f f e c t s a r e symptoms o f abnormal p h y s i o l o g i c a l r e a c t i o n s t h a t have o c c u r r e d a t the c e l l u l a r l e v e l . They d e c r e a s e t h e o v e r a l l q u a l i t y o f a c r o p commodity and t h e r e f o r e c o n s t i t u t e an economic l o s s t o t h e f a r m e r o r t h e r e t a i l e r . Two t y p e s o f p o s t - h a r v e s t p h y s i o l o g i c a l d i s o r d e r s a r e commonly r e c o g n i s e d : ( i ) d i s o r d e r s , w h i c h I s h a l l c a l l Type I b e l o w , w h i c h can be a t t r i b u t e d t o p r e h a r v e s t c o n d i t i o n s . ( i i ) d i s o r d e r s (Type II) w h i c h owe t h e i r o r i g i n t o imposed e x t e r n a l c o n d i t i o n s o f s t o r a g e a f t e r - 7 -t h e commodity has been p i c k e d ( W i l k i n s o n 197 0 ) . However, a t t h e i n t e r f a c e between t h e above two t y p e s o f p o s t -h a r v e s t d i s o r d e r s , t h e r e i s a t h i r d c a t e g o r y : ( i i i ) d i s o r d e r s (Type I I I ) w h i c h can be a t t r i b u t e d t o t h e p o s t - h a r v e s t b u t p r e - s t o r a g e c o n d i t i o n s . Type I p o s t - h a r v e s t d i s o r d e r s a r e e x t e r n a l l y l a t e n t b e f o r e s t o r a g e . They become n o t i c e a b l e d u r i n g o r a f t e r s t o r a g e . They c a n be c r u d e l y s u b d i v i d e d i n t o two c a t e g o r i e s , c u l t u r a l and n o n - c u l t u r a l , on t h e b a s i s o f t h e t y p e o f p r e -d i s p o s i n g e n v i r o n m e n t a l f a c t o r s . C u l t u r a l f a c t o r s a r e p r e d i s p o s i n g f a c t o r s w h i c h can be c o n t r o l l e d o r l a r g e l y m o d i f i e d by t h e g r o w e r . They i n c l u d e : s o i l t e x t u r e and a e r a t i o n w h i c h can be m a n i p u l a t e d t h r o u g h methods o f c u l t i v a t i o n ; s o i l m o i s t u r e and n u t r i e n t s w h i c h can be c o n t r o l l e d by i r r i g a t i o n and f e r t i l i z e r a p p l i c a t i o n ; b i o l o g i c a l f a c t o r s w h i c h can be managed by h o r m o n a l , p e s t i c i d a l o r h e r b i c i d a l s p r a y a p p l i c a t i o n s o r by c h o i c e o f c u l t i v a r , d a t e o f h a r v e s t , r o o t s t o c k , s p a c i n g , c r o p r o t a t i o n and p r u n i n g . I n d i v i d u a l l y , one c u l t u r a l f a c t o r may n o t be d i r e c t l y r e s p o n s i b l e f o r a s p e c i f i c d i s o r d e r , s i n c e t h e f a i l u r e o f one p r a c t i c e may be r e m e d i e d by a n o t h e r . However, t h e combined e f f e c t o f two o r more f a c t o r s e s p e c i a l l y u n d e r a d v e r s e e n v i r o n m e n t a l c o n d i t i o n s may p r o d u c e h a r v e s t e d c o m m o d i t i e s w h i c h r e s p o n d p o o r l y t o subsequent s t o r a g e c o n d i t i o n s . - 8 -A large number of Type I disorders can be traced to mineral n u t r i t i o n during growth and development. For example, B i t t e r P i t of apples has been shown to be due to low calcium levels (De Long 1936, Askew et a l . 1960, Chittenden et a l . 1969) and over-application of potassium (Wilkinson 197 0). Low calcium lev e l s also r e s u l t in Water Core Breakdown of apples (Sharpies 1967). Also, "early picking" has been demonstrated to contribute to those two disorders and t h i s e f f e c t i s most l i k e l y due to the interruption of f r u i t n u t r i t i o n . Type I physiological disorders can also be caused by pre-harvest environmental factors which are not generally subject to c u l t u r a l control. Such non-cultural factors include r a i n f a l l , temperature, l i g h t , wind and elevation. Greenback or Solar Yellowing, a condition of u n i l a t e r a l poor colour development in the tomato, re s u l t s from exposure to "short wave" radiation (Lipton 1970). The disorder i s not c l e a r l y evident unless f r u i t s are ripe. F r u i t s harvested green therefore exhibit the disorder i n storage, but induction of the disorder takes place e a r l i e r i n the f i e l d . S i m i l a r l y , water-stress i n the f i e l d has been shown to cause both B i t t e r P i t of apples (Wilkinson 1970) and Endoxerosis of oranges and lemons (Brooks and McColloch 193 7). Some other disorders such as the Endogenous Brown Spot of pineapple are induced by c h i l l i n g at low f i e l d temperatures. The disorder has no v i s i b l e symptoms in storage but exhibits the t y p i c a l symptom at ambient temperatures aft e r storage (Dull 1971). Type I I p o s t - h a r v e s t d i s o r d e r s a r e e s s e n t i a l l y due t o r e a c t i o n s o f t h e c r o p commodity t o t h e s t o r a g e e n v i r o n m e n t . Modern c r o p s t o r a g e i s b a s e d on t h e m a n i p u l a t i o n o f t e m p e r a t u r e and t h e gaseous a t m o s p h e r e , and most s t o r a g e - i n d u c e d d i s o r d e r s can be l i n k e d t o t h e s e two f a c t o r s . Watery Breakdown o f c i t r u s ( M i l l e r 1 9 4 6 ) , and C h i l l i n g I n j u r y o f banana (Wardlaw 1961, M i r a t a and Ku 1966) o r papaya ( P a n t a s t i c o 1975) a r e d i s o r d e r s c a u s e d by low b u t n o n - f r e e z i n g s t o r a g e t e m p e r a t u r e s . Ammonia I n j u r y , i s d i s t i n g u i s h e d by marked d i s c o l o r a t i o n o f v a r i o u s commodities and i t o c c u r s f o l l o w i n g a c c i d e n t a l e x p o s u r e t o ammonia d u r i n g c o l d s t o r a g e ( P a n t a s t i c o e t a l . 1975). C o n t r o l l e d atmosphere d i s o r d e r s , on the o t h e r h a n d , can a r i s e from low oxygen l e v e l s as i n B l a c k h e a r t o f p o t a t o e s ( P a n t a s t i c o e t a l . 1 9 7 5 ) and Brown-Core o f a p p l e s and p e a r s . A n o t h e r group o f c o n t r o l l e d atmosphere d i s o r d e r s , i s due t o e x c e s s i v e l y h i g h c a r b o n - d i o x i d e l e v e l s w h i c h p r o d u c e b r o w n i n g as i n C o r e f l u s h o f a p p l e s , Brownheart o f p e a r s and o f f - f l a v o u r s i n s t r a w b e r r y and many o t h e r f r u i t s . O f f - f l a v o u r s a r e p r o b a b l y l i n k e d t o e t h a n o l a c c u m u l a t i o n ( U l r i c h 1975). Type I I I p o s t - h a r v e s t p h y s i o l o g i c a l d i s o r d e r s o c c u r a f t e r t e r m i n a t i o n o f growth and development b u t b e f o r e s t o r a g e . They i n c l u d e i n j u r i e s s u s t a i n e d by c r o p s d u r i n g h a r v e s t , as w e l l as o t h e r d i s o r d e r s t r a c e a b l e t o e n v i r o n m e n t a l c o n d i t i o n s p r i o r t o s t o r a g e . - 10 -The p e r i o d between h a r v e s t and s t o r a g e i s e s p e c i a l l y c r i t i c a l f o r t h e q u a l i t y o f a commodity w h i c h i s n o t i n t e n d e d f o r immediate c o n s u m p t i o n . Improper methods o f h a r v e s t i n g , r o u g h p o s t - h a r v e s t h a n d l i n g p r o c e d u r e s , d e l a y i n t r a n s f e r t o s t o r a g e and i n t e r i m e x p o s u r e t o a d v e r s e e n v i r o n m e n t a l c o n d i t i o n s can r e n d e r subsequent s t o r a g e i n e f f e c t i v e . H a r v e s t i n g and h a n d l i n g p r o c e d u r e s must m i n i m i s e s k i n a b r a s i o n and t i s s u e b r u i s i n g i n o r d e r t o s u p p r e s s t i s s u e breakdown and m i c r o b i a l a t t a c k . D e l a y i n t r a n s f e r t o s t o r a g e w i t h o u t immediate r e m o v a l o f f i e l d h e a t l e a d s t o s h r i n k a g e , d e h y d r a t i o n and r e d u c e d s t o r a g e c a p a b i l i t y o f f r u i t s and v e g e t a b l e s . " D e l a y t o s t o r a g e " has been c l a i m e d t o cause a number o f p o s t - h a r v e s t d i s o r d e r s s u c h as t h e Stem End R i n d Breakdown o f o r a n g e s , T r a n s l u c e n t S c a l e s o f o n i o n s ( P a n t a s t i c o e t a l . 1975) and A p p l e S c a l d (Meigh 1970). A l t h o u g h t h e p r i m a r y c a u s e s o f t h e s e d i s o r d e r s have n o t been t h o r o u g h l y i n v e s t i g a t e d , some o f them a r e p r o b a b l y i n d u c e d by low r e l a t i v e h u m i d i t y (McCornack 197 0) and h i g h t e m p e r a t u r e . H i g h ambient t e m p e r a t u r e s d u r i n g t h e p e r i o d between h a r v e s t i n g and s t o r a g e can i n d u c e p i t t i n g i n banana ( P a n t a s t i c o 1975) as w e l l as s u r f a c e b r o w n i n g , an o b j e c t i o n a b l e b r o w n i n g c o n d i t i o n due t o t h e o x i d a t i o n o f t i s s u e s a t m e c h a n i c a l l y i n j u r e d a r e a s , o f p o t a t o e s ( G u l l 1966). - 11 -E l e c t r o m a g n e t i c R a d i a t i o n The sun e m i t s r a d i a n t energy w h i c h i s the u l t i m a t e s o u r c e o f energy needed t o s u s t a i n l i f e . Most o f the r a d i a t i o n e m i t t e d by the sun o c c u r s a t w a v e l e n g t h s between 300nm and 3000 nm. The i n t e n s i t y o f u l t r a v i o l e t r a d i a t i o n r e a c h i n g the e a r t h ' s s u r f a c e from t h e sun i s r e d u c e d due t o a b s o r p t i o n by a t m o s p h e r i c o z o n e . I n f r a r e d r a d i a t i o n i s r e d u c e d by a b s o r p t i o n by a t m o s p h e r i c w a t e r v a p o u r , c a r b o n d i o x i d e and o z o n e . R a l e i g h and Mie p a r t i c l e s c a t t e r i n g , as w e l l as a b s o r p t i o n and s c a t t e r i n g by c l o u d s , a l s o c o n t r i b u t e t o t h e a t t e n u a t i o n o f s o l a r r a d i a t i o n i n t h e e a r t h ' s atmosphere (Campbell 1977, M o n t e i t h 1973, Treshow 1972). A p p r o x i m a t e l y 2% o f t h e photons r e c e i v e d a t t h e e a r t h ' s s u r f a c e a r e i n t h e u l t r a v i o l e t , 45% i n the v i s i b l e and 53% i n t h e i n f r a r e d (Nobel 1974). r e l a t i v e l y h i g h v o l u m e t r i c h e a t c a p a c i t y (Nobel 197 4 ) . They can a l s o be t r e a t e d as " f u l l r a d i a t o r s " o r " b l a c k b o d i e s " s i n c e t h e y a b s o r b at a l l w a v e l e n g t h s ( M o n t e i t h 197 3 ) . As a r e s u l t o f t h e i r s u r f a c e t e m p e r a t u r e s t h e y e m i t long-wave r a d i a t i o n ( l o n g e r t h a n 4um) a c c o r d i n g t o P l a n c k ' s s p e c t r a l d i s t r i b u t i o n law: * Most n a t u r a l s u r f a c e s , s u c h as t h e s o i l , have a B (Campbell 1977) - 12 --2 where: L ( W m )= s p e c t r a l e m i t t a n c e (or e n e r g y f l u x d e n s i t y a p e r u n i t w a v e l e n g t h ) -23 k = Boltzmann c o n s t a n t (1.38 x 10 J / K ) -34 h = P l a n c k ' s c o n s t a n t (6.63 x 10 J s) c = Speed o f l i g h t (3 x 1 0 8 m S - 1 ) T = T e m p e r a t u r e o f B l a c k b o d y . A = W a v e l e n g t h I t f o l l o w s from t h e above f o r m u l a , t h a t t h e w a v e l e n g t h o f peak e m i t t a n c e , A max o f t h e i r e m i s s i o n s p e c t r u m , a l s o l i e s i n t h e f a r i n f r a r e d (about lOum) a c c o r d i n g t o W i e n ' s d i s p l a c e m e n t law: A 2897 max = T >™ In m i c r o m e t e o r o l o g y , r a d i a t i o n i s o f t e n d i v i d e d i n t o s h o r t wave (0.3 - 3 urn) and l o n g wave (3 - 100 urn) r a d i a t i o n ( M o n t e i t h 197 3, C a m p b e l l 1977). The d i v i s i o n i s a r b i t r a r y b u t i t i s aimed a t s e p a r a t i n g t h e r a d i a t i o n from the sun from r a d i a t i o n o r i g i n a t i n g from t e r r e s t r i a l s u r f a c e s . Sometimes, however, b i o l o g i s t s have u s e d t h e t e r m " s h o r t wave" synonymously w i t h r a d i a t i o n from 0.3 t o 0.7 um ( L i p t o n 1970). W i t h i n t h i s t h e s i s , the term " r a d i a n t e n e r g y " w i l l g e n e r a l l y r e f e r t o r a d i a t i o n i n the waveband 200 nm t o 3000 nm o r i g i n a t i n g from a l i g h t e m i t t i n g s o u r c e , e i t h e r a r t i f i c i a l o r s o l a r . The f o l l o w i n g s e c t i o n w i l l r e v i e w some i n j u r i o u s e f f e c t s o f e l e c t r o m a g n e t i c r a d i a t i o n t r e a t m e n t s and t h e e f f e c t s i n c l u d e b o t h t h e r m a l as w e l l as n o n - t h e r m a l e x a m p l e s . - 13 -A b s o r p t i o n o f E l e c t r o m a g n e t i c R a d i a t i o n A p h o t o n o f r a d i a n t e n e r g y can p r o d u c e p h o t o c h e m i c a l and hence b i o l o g i c a l e f f e c t s o n l y i f i t i s a b s o r b e d (Lamola and T u r r o 1977). A b s o r p t i o n o f r a d i a n t e n e r g y i s m e d i a t e d by t h e p r e s e n c e o f u n s a t u r a t e d g r o u p s o r c o m b i n a t i o n s o f such groups i n c h r o m o p h o r i c s y s t e m s . In o r d e r f o r a quantum o f r a d i a n t e n e r g y t o be a b s o r b e d , i t s e n e r g y c o n t e n t must be e q u a l t o the energy d i f f e r e n c e between t h e e l e c t r o n i c g r o u n d s t a t e and one o f t h e e x c i t a t i o n l e v e l s o f t h e chromophore (Thomas 1972). The a b s o r b e d p h o t o n r a i s e s a v a l e n c e e l e c t r o n o f t h e chromophore from the g r o u n d s t a t e ( e . g . TT o r b i t a l ) t o an e x c i t e d s t a t e ( e . g . TT * ) • The e x c i t e d m o l e c u l e o r p a r t o f t h e m o l e c u l e can l o s e e n e r g y o b t a i n e d from p h o t o n a b s o r p t i o n and r e t u r n t o i t s ground s t a t e b y : ( i ) c o n v e r t i n g i t s e l e c t r o n i c e x c i t a t i o n a l energy i n t o v i b r a t i o n a l e n e r g y (heat) o f i t s e l f o r n e a r b y m o l e c u l e s , ( i i ) e m i t t i n g a p h o t o n ( f l u o r e s c e n c e o r p h o s p h o r e s -cence) o r ( i i i ) p r o d u c i n g a c h e m i c a l r e a c t i o n w h i c h may i n v o l v e e i t h e r a r e a r r a n g e m e n t o f the a b s o r b i n g m o l e c u l e t o a new s t a b l e form o r t r a n s f e r o f energy ( e l e c t r o n i c o r v i b r a t i o n a l ) t o a n o t h e r m o l e c u l e w h i c h t h e n u n d e r g o e s a s t a b l e change i n s t r u c t u r e . - 14 -t Photopigments, in contrast to ordinary pigments can also produce two other phenomena apart from heat production and fluorescence emission: the converted energy may be used instantaneously for chemical or physical processes or may be temporarily stored and l a t e r used for d r i v i n g energy-requiring processes. In the f i r s t case there exist three p o s s i b i l i t i e s : (a) energy conversion i s used for t r i g g e r i n g a reaction (b) conversion can r e s u l t in the transformation of the photopigment 1 into a catalyst, and (c) a product suitable for use in chemical reactions i s generated by the energy conversion (Thomas 1972) . In chromophores containing conjugated double bonds, the higher the number of conjugated unsaturated centres the lower the energy separation between the II o r b i t a l s and the 77 * o r b i t a l s (Nobel 197 4); hence the longer (lower energy) the wavelengths at which the compound absorbs. Thus, ethylene absorbs at 200 nm, benzene at 280 nm, carotene at 450 nm and porphyrins at 600 nm. The presence of water lowers the energy of the 7f * electrons and hence the t r a n s i t i o n from 7j to 7T * involves l e s s energy. Thus, i n the presence of water, absorption further s h i f t s towards lower energy (longer) wavelengths. Comprehensive texts on mechanisms of radiant energy absorption are provided by Clayton (1970), Nobel (1974) and by Lamola and Turro (1977). The absorption of v i s i b l e radiation i s due to the presence of a photosensitizer. Two types of photosensitized reactions are generally recognized in b i o l o g i c a l systems: - 15 -non-oxygen r e q u i r i n g p h o t o s e n s i t i z a t i o n r e a c t i o n s , w h i c h do n o t o c c u r i n h i g h e r p l a n t s , and s e n s i t i z e d p h o t o o x i d a t i o n r e a c t i o n s , o r photodynamic a c t i o n s . The e n e r g y a b s o r b e d by t h e p h o t o s e n s i t i z e r c a n k i l l t h e c e l l s d u r i n g p h o t o -dynamic r e a c t i o n s . Endogenous c h l o r o p h y l l i s t h e p h o t o -s e n s i t i z e r i n h i g h e r p l a n t s b u t under o r d i n a r y c o n d i t i o n s , c h l o r o p l a s t components a r e p r o t e c t e d from p h o t o o x i d a t i o n by h i g h c o n c e n t r a t i o n o f c a r o t e n o i d s ( K r i n s k y 1968, S p i k e s 1968). In a d d i t i o n , i n t h e c u t i c l e , wax and s u b e r i n h e l p t o p r o t e c t t h e i n t e r n a l t i s s u e s from e x c e s s i v e l i g h t e s p e c i a l l y where the c a r o t e n o i d s a r e p o o r l y d e v e l o p e d as i n shade p l a n t s ( L e v i t t 1972). j I n j u r i o u s E f f e c t s o f R a d i a n t E n e r g y E f f e c t s o f U l t r a v i o l e t (UV) R a d i a t i o n Much o f t h e l i t e r a t u r e on t h e i n j u r i o u s e f f e c t s o f r a d i a t i o n i s c o n c e r n e d w i t h u l t r a v i o l e t (UV) r a d i a t i o n . UV r a d i a t i o n between a b o u t 200 nm and 300 nm i s a b s o r b e d by p r o t e i n s and n u c l e i c a c i d s and t h i s p r o d u c e s damaging e f f e c t s on c e l l s . The p o t e n t i a l l y l e t h a l damage o f DNA by u l t r a v i o l e t r a d i a t i o n i s p r i m a r i l y due t o w a v e l e n g t h s s h o r t e r t h a n 310 nm, b u t l o n g e r UV w a v e l e n g t h s have a l s o been found t o c o n t r i b u t e t o t h e o v e r a l l e f f e c t ( T y r e l l 1974) . - 16 -Brabham e t a l . (1974) found t h a t tomato f r u i t s i r r a d i a t e d a t t h e mature g r e e n s t a g e r e t a i n e d g r e e n c o l o u r i n i r r a d i a t e d a r e a s a f t e r t h e f r u i t s r i p e n e d . The p e r i c a r p i n the i r r a d i a t e d a r e a s f a i l e d t o s y n t h e s i z e t h e r e d p i g m e n t , l y c o p e n e , a s s o c i a t e d w i t h r i p e n i n g . I r r a d i a t i o n a l s o p r o d u c e d c h l o r o s i s , t i s s u e d e a t h and pigment b l e a c h i n g i n l e a v e s d e t a c h e d from t e n d i f f e r e n t s p e c i e s o f h i g h e r p l a n t s . Of t h e t o t a l amount o f photons i n c i d e n t on the e a r t h ' s a t m o s p h e r e , however, o n l y a s m a l l f r a c t i o n i s i n t h e UV r e g i o n ( M o n t e i t h 1973). A l s o , most o f t h a t i s a b s o r b e d by a t m o s p h e r i c o z o n e , e s p e c i a l l y a t w a v e l e n g t h s l e s s t h a n 300 nm, b e f o r e i t r e a c h e s t h e s u r f a c e o f t h e e a r t h . I t i s n o t c e r t a i n i f the e a r t h ' s s u r f a c e r e c e i v e s r a d i a t i o n below 290 nm a t any a l t i t u d e . F u r t h e r m o r e , UV r a d i a t i o n p e n e t r a t e s o n l y v e r y s l i g h t l y t h r o u g h p l a n t t i s s u e s s i n c e most p l a n t p a r t s a r e g e n e r a l l y opaque t o r a d i a t i o n s l e s s t h a n 350 nm (Ruhland 1961). I t i s d o u b t f u l whether t h e amounts o f UV r a d i a t i o n t h a t have sometimes been employed i n l a b o r a t o r y e x p e r i m e n t s can e v e r be e n c o u n t e r e d i n n a t u r a l t e r r e s t r i a l e n v i r o n m e n t s . The e f f e c t o f u l t r a v i o l e t r a d i a t i o n on p l a n t s i s g e n e r a l l y c o n s i d e r e d o f r e l a t i v e m i n o r e c o l o g i c a l i m p o r t a n c e (Daubenmire 1974). E f f e c t s V i s i b l e R a d i a t i o n P r e - h a r v e s t e f f e c t s — P l a n t s have an a b s o l u t e l i g h t r e q u i r e m e n t f o r growth and d e v e l o p m e n t . L i g h t e l i c i t s d i r e c t l y - 17 -or i n d i r e c t l y enormous number of responses i n plants during ontogeny. Processes i n which the d i r e c t involvement of l i g h t has been demonstrated include photic growth reactions such as: (a) photosynthesis and (b) photomorphogenetic processes which include photoperiodism and the wide array of phytochrome-mediated responses (Altraan and Dittmer 1975). Light i s also involved i n a t h i r d category of processes termed photomotive processes, which include phototropism, phototaxis and photonasty (Thomas 1972). It i s not cle a r i f "excess l i g h t " per se induces injury on plants during growth and development since plants seem to be adapted to the various ecological zones where they e x i s t . "High l i g h t i n t e n s i t y " has been implicated i n leaf chlorophyll destruction and disorders such as the sunscald of tomatoes. However the r e a l cause of such disorders seems to be more of temperature than l i g h t since at no time were the i n j u r i e s induced in the absence of high temperatures (Antropova 1966; Lipton 1970) The sunscald injury i s examined separately i n t h i s review. Hager (1957) and Kislyuk (1963, 1964) reported l i g h t damage to plant c e l l s at low temperatures and concluded that the role of l i g h t i s that of a photooxidizing agent of l i v i n g protoplasmic components at the expense of l i g h t energy which i s not used for photosynthesis under low temperature conditions. - 18 -P o s t - h a r v e s t E f f e c t s — E x p o s u r e o f p o t a t o t u b e r s t o l i g h t d u r i n g s t o r a g e i n d u c e s g r e e n i n g i n t h e t u b e r s due t o c h l o r o p h y l l f o r m a t i o n (Conner 1937, P a t i l e t a^. 1971). A p a r t from t h i s e f f e c t , most o f t h e l i t e r a t u r e on t h e p o s t -h a r v e s t r e s p o n s e s t o v i s i b l e r a d i a t i o n has c o n c e n t r a t e d m a i n l y on r i p e n i n g because o f t h e o b v i o u s i m p o r t a n c e o f c o l o u r i n q u a l i t y o f f r u i t s w h i c h undergo r i p e n i n g f o l l o w i n g m a t u r i t y . Tomato f r u i t s w i l l r i p e n i n t h e d a r k (Denisen 1948) b u t i l l u m i n a t i o n p r o d u c e s " r e d d e r " c o l o u r and h i g h e r c a r o t e n o i d l e v e l s (McCollum 1954, N e t t l e s e t a l . 1955). The s p e c t r a l q u a l i t y o f v i s i b l e l i g h t has been shown t o a f f e c t t h e c o l o u r development o f d e t a c h e d mature g r e e n tomatoes (Smith 1936, S h a w f e l t and H o l p i n 1967, S b e w f e l t 1970', K h u d a i r i 1972). B l u e and r e d monochromatic l i g h t s enhance c a r o t e n o i d s y n t h e s i s i n tomatoes more t h a n w h i t e and g r e e n l i g h t i n t h a t o r d e r (Jen 1974). The e f f e c t i v e n e s s o f b l u e l i g h t i n e n h a n c i n g c a r o t e n o i d s y n t h e s i s i s due t o c a r o t e n o i d a b s o r p t i o n maxima w h i c h l i e i n t h e b l u e r e g i o n o f t h e s p e c t r u m ( V e t t e r e t al_. 1971) . On t h e o t h e r h a n d , r e d l i g h t a c c e l e r a t e s c h l o r o p h y l l b i o - d e g r a d a t i o n . Recent s t u d i e s by J e n and h i s c o w o r k e r s have c o n f i r m e d t h a t t h e tomato r i p e n i n g i s p a r t l y a p h y t o c h r o m e - m e d i a t e d p r o c e s s (Thomas and J e n 1975, J e n e t a l . 1977). E f f e c t s o f I n f r a r e d R a d i a t i o n A r t h u r (1932) r e p o r t e d t h a t a p p l e s exposed t o i n f r a r e d r a d i a t i o n from a 500 W Mazda lamp a t an a i r t e m p e r a t u r e o f 2°C - 19 -d e v e l o p e d a w r i n k l e d n e c r o t i c a r e a a t t h e s i d e exposed t o r a d i a t i o n f i v e days l a t e r , whereas t h e v i s i b l e l i g h t from the same lamp p r o d u c e d no i n j u r y . H i s r e s u l t s showed t h a t i n t e r n a l f r u i t t e m p e r a t u r e was a b o u t 20°C above a i r t e m p e r a t u r e b u t he s u g g e s t e d t h a t s u c h a t e m p e r a t u r e was n o t h i g h enough t o cause t h e i n j u r y . Ramsey (1930) o b s e r v e d " s u n s c a l d " on o n i o n s h a r v e s t e d and exposed t o s u n l i g h t i n c r a t e s . L e C l e r g e (1931) a l s o n o t e d s u n s c a l d on honeydew melons exposed t o s u n l i g h t a f t e r the l e a v e s had been k i l l e d by f u n g i . B o t h a t t r i b u t e d the e f f e c t t o i n f r a r e d r a d i a t i o n . R e c e n t l y , L i p t o n (1970) s t u d i e d t h e i n c i d e n c e o f c o l o u r d e f e c t s i n r i p e tomato f r u i t s grown i n the g r e e n h o u s e . In h i s e x p e r i m e n t , f r u i t s were e i t h e r shaded by l e a v e s o r e x p o s e d . Among t h e exposed f r u i t s , u n p a i n t e d f r u i t s had a h i g h e r i n c i d e n c e o f d e f e c t i v e c o l o r a t i o n t h a n f r u i t s t h a t were p a i n t e d b l a c k , w h i c h i n t u r n had a h i g h e r number o f d e f e c t s t h a n f r u i t s p a i n t e d w h i t e . L i p t o n , t h e r e f o r e , c o n c l u d e d t h a t t h e d e f e c t i v e c o l o r a t i o n on exposed f r u i t s was c a u s e d by " s h o r t wave" ( v i s i b l e ) i n f r a - r e d r a d i a t i o n . Burns (1933) a l s o showed t h a t i n f r a - r e d r a d i a t i o n a t w a v e l e n g t h s l o n g e r t h a n 1100 nm was d e t r i m e n t a l t o p h o t o s y n t h e s i s . He a r g u e d t h a t t h e t e m p e r a t u r e c o e f f i c i e n t o f p h o t o s y n t h e s i s a t 28°C was so n e a r one t h a t t h e r e s p o n s e c o u l d n o t be due t o t e m p e r a t u r e . - 20 -One major c o n s t r a i n t i n i n t e r p r e t i n g t h e r e s u l t s o f e x p e r i m e n t s r e p o r t e d i n t h e l i t e r a t u r e on t h e e f f e c t s o f s o l a r r a d i a t i o n l i e s i n t h e d i f f i c u l t y o f s e p a r a t i n g r a d i a t i o n e f f e c t s from t h e r m a l e f f e c t s . C o n s e q u e n t l y , many h i g h t e m p e r a t u r e e f f e c t s i n d u c e d by s o l a r r a d i a t i o n have been r e f e r r e d t o as v i s i b l e r a d i a t i o n e f f e c t s and v i c e v e r s a . F o r example, i n c r e a s e d f r u i t s i z e , i m p r o v e d s t o r a g e p r o p e r t i e s and b e t t e r c o l o u r development i n a p p l e s were i n i t i a l l y a t t r i b u t e d t o s u n l i g h t ( H e i n i c k e 1966, J a c k s o n et_ a l . 1971) b u t were l a t e r d e m o n s t r a t e d t o be due t o h i g h t e m p e r a t u r e s ( T h o r p e e 1 9 7 4 ) . S i m i l a r l y , W o r t h i n g t o n e t a l . (1969) s t u d i e d t h e e f f e c t s o f l i g h t and t e m p e r a t u r e s on tomato r i p e n i n g and l i n k e d i n c r e a s e d c o l o u r development o f t h e r i p e n i n g tomatoes t o e l e v a t e d t e m p e r a t u r e s . Subsequent s t u d i e s have shown t h a t t h e r e s p o n s e i s a r a d i a t i o n e f f e c t and t h a t i t i s p a r t l y under t h e c o n t r o l o f phytochrome (Jen 1974, Thomas and J e n 1975). E x p o s u r e o f p l a n t p a r t s t o d i r e c t s o l a r r a d i a t i o n r e s u l t s i n t i s s u e t e m p e r a t u r e s w e l l above a i r t e m p e r a t u r e s and t h e magnitude o f t h e t e m p e r a t u r e i n c r e a s e depends on the r a d i a t i o n l o a d , a i r movement, t i s s u e t h i c k n e s s and r e f l e c t i n g c h a r a c t e r i s t i c s o f t h e s u r f a c e (Ansare and Loomis 1959, S a l i s b u r y and Spomer 1964, T r a n q u i l l i n i 1 9 6 4 ) . T h u s , d i f f e r e n t p a r t s o f t h e same p l a n t may have d i f f e r e n t t e m p e r a t u r e s and the t i s s u e s d i r e c t l y exposed t o t h e most i n t e n s e r a d i a t i o n t e n d t o r e a c h t h e h i g h e s t t e m p e r a t u r e s . F r u i t t e m p e r a t u r e s i n the - 21 -f i e l d can r i s e s i g n i f i c a n t l y above a i r temperatures (Schroeder 1965, H a l l 1964, McGillivray 1934) e s p e c i a l l y at low wind speeds (Thorpe 1974). It i s therefore not cert a i n to what extent the injurious e f f e c t s of infra-red radiation reported i n the l i t e r a t u r e are due to inf r a - r e d radiation per se or to the high temperatures produced i n tissues by inf r a - r e d radiation. More than any other part of the spectrum, "infra-red" effects are d i f f i c u l t to separate from "thermal" e f f e c t s since radiation i n the inf r a - r e d i s absorbed by water i n the tissues and i s e f f i c i e n t l y converted into heat. Short wave in f r a - r e d radiation i s also more e f f e c t i v e than longwave radiation i n inducing temperature changes i n the tissues on a quantum basis since i t contains more energy (Planck's r e l a t i o n s h i p ) . Biophysical and Chemical Basis for High Temperature Ef f e c t s L e v i t t (1972) i d e n t i f i e d four mechanisms for the induction of primary heat injury: changes i n metabolic reaction rates, protein denaturation, increased l i p i d mobility and chemical decomposition. High temperatures can disrupt metabolism i n many ways. It can cause the accumulation of toxic reaction products, the depletion of e s s e n t i a l metabolites and the i r r e v e r s i b l e coagulation of protoplasmic macromolecules (Alexandrov 1977). - 22 -Temperature a l s o a f f e c t s b o t h t h e s t r u c t u r a l i n t e g r i t y of . s e m i - p e r m e a b l e membranes as w e l l as m e t a b o l i c a l l y - d e p e n d e n t a c t i v e t r a n s p o r t . In t h e t o m a t o , d e c r e a s e d t e m p e r a t u r e l e a d s t o d e c r e a s e d m i n e r a l u p t a k e by t h e p l a n t , t h u s s u g g e s t i n g a r e s t r i c t i o n due t o l i m i t e d energy s u p p l y from m e t a b o l i s m o r p o s s i b l y an e f f e c t o f i n c r e a s e d p r o t o p l a s m i c v i s c o s i t y ( L a n g r i d g e and M c W i l l i a m 1967). S u p r a - o p t i m a l t e m p e r a t u r e s i n c r e a s e t h e r e l e a s e o f w a t e r - s o l u b l e s u b s t a n c e s from c e l l s p r o b a b l y due t o t h e d i s o r g a n i z a t i o n o f c e l l u l a r membranes. T e m p e r a t u r e a l s o a f f e c t s t h e p r o t o p l a s m t h r o u g h i t s i n f l u e n c e on t h e i n t r a c e l l u l a r water c o n t e n t , water s t r u c t u r e and w a t e r - b i n d i n g ( L a n g r i d g e and M c W i l l i a m 1967). L i v i n g p r o t o p l a s m g e n e r a l l y c o n t a i n s a b o u t 20% p r o t e i n and 70-80% water ( L i n g 1967). W i t h i n p h y s i o l o g i c a l l i m i t s i n c r e a s e d t e m p e r a t u r e promotes g e l a t i o n and s t a b i l i z e s the c o n f i g u r a t i o n o f membranes (Kavanau 1965). P r o t o p l a s m i c v i s c o s i t y a l s o changes w i t h t e m p e r a t u r e b u t t h e p a t t e r n o f such changes has n o t been c o n s i s t e n t among d i f f e r e n t s t u d i e s . B o t h an i n c r e a s e and a d e c r e a s e i n v i s c o s i t y w i t h i n c r e a s i n g t e m p e r a t u r e have been r e p o r t e d . I t has been s u g g e s t e d t h a t p r o t o p l a s m i c v i s c o s i t y m i g h t be i n f l u e n c e d by i n t r a c e l l u l a r c o n t r o l mechanisms ( F r e y - W y s s l i n g 1952). P r o t o p l a s m i c s t r e a m i n g i n c r e a s e s w i t h t e m p e r a t u r e up t o t h e optimum t e m p e r a t u r e , t h e n i t d e c r e a s e s and c e a s e s a l t o g e t h e r above 40°C ( L e v i t t 1972). S u p r a - o p t i m a l t e m p e r a t u r e s l e a d t o enzyme i n a c t i v a t i o n , d e n a t u r a t i o n , r e d u c e d enzyme s y n t h e s i s and t h e u n c o u p l i n g o f - 23 -o x i d a t i o n and p h o s p h o r y l a t i o n i n c h l o r o p l a s t s and m i t o c h o n d r i a (Emmett and Walker 19 6 9 ) . In g r o w i n g p l a n t s , a p a r t from d e n a t u r a t i o n and t h e m e c h a n i c a l e f f e c t s o f h i g h t e m p e r a t u r e s on c e l l s , t h e r m a l damage may o c c u r from t h e i n a c t i v a t i o n o f t h e e l e c t r o n t r a n s p o r t systems ( B e l i k o v e t a l . 1963) and the p r o d u c t i o n o f i n t r a c e l l u l a r u n c o u p l i n g a g e n t s (Semikhatova and Bushuyeva 19 6 3 ) . The h e a t t o l e r a n c e o f some o r g a n i s m s has been found t o be p r o p o r t i o n a l t o t h e i r l i p i d s a t u r a t i o n . L e v i t t (1972) s u g g e s t e d t h a t h i g h t e m p e r a t u r e damage may be due t o e x c e s s i v e f l u i d i t y o f t h e l i p i d s , l e a d i n g t o a d i s r u p t i o n o f t h e l i p i d l a y e r and hence l o s s o f s e m i p e r m e a b i l i t y . A n o t h e r a t t e m p t t o e x p l a i n t h e mechanism o f h e a t i n j u r y has been t h e e x t e n s i o n o f t h e s u l p h y d r y l group o x i d a t i o n t h e o r y t o a c c o u n t f o r t h e r m a l damage. L e v i t t (1962) s u g g e s t e d t h a t h i g h t e m p e r a t u r e s p r o b a b l y i n d u c e h e a t i n j u r y by i n c r e a s i n g m o l e c u l a r movement and r e m o v i n g bound w a t e r , t h u s a l l o w i n g p r o t e i n s t o a p p r o a c h c l o s e enough t o a l l o w i n t e r m o l e c u l a r d i s u l p h i d e bond f o r m a t i o n t o o c c u r . I n j u r i o u s E f f e c t s o f H i g h T e m p e r a t u r e s Normal m e t a b o l i c a c t i v i t y i n most p l a n t s p e c i e s i s r e s t r i c t e d t o a narrow range o f t e m p e r a t u r e from about 0°C t o 50°C even though t h e range o f s h o r t term p l a n t s u r v i v a l extends from below -30°C f o r s u b a r c t i c c o n i f e r s t o about 60°C f o r d e s e r t - 24 -s h r u b s ( O o s t i n g 1958). D i f f e r e n t s p e c i e s have d i f f e r e n t optimum t e m p e r a t u r e s (optimum t e m p e r a t u r e b e i n g t h e t e m p e r a t u r e a t w h i c h a p r o c e s s can be " p e r m a n e n t l y " m a i n t a i n e d w i t h o u t a d e c r e a s e i n r a t e (Blackman 1905)) and w i t h i n a p a r t i c u l a r s p e c i e s , o p t i m a l t e m p e r a t u r e s t e n d t o d e c r e a s e w i t h age b u t i n c r e a s e w i t h i n c r e a s i n g l i g h t i n t e n s i t i e s (Camus and Went 1952, Went 1957). P l a n t s , i n t h e i r n a t u r a l s t a t e , a r e o f t e n n o t v i s i b l y a f f e c t e d by s m a l l t e m p e r a t u r e changes s i n c e t h e y p o s s e s s h o m e o s t a t i c mechanisms w h i c h t e n d t o b u f f e r them a g a i n s t e n v i r o n m e n t a l f l u c t u a t i o n s . However, l a r g e r t e m p e r a t u r e changes may i n d u c e p h e n o t y p i c a l t e r a t i o n s i n c e r t a i n p l a n t p a r t s ( L a n g r i d g e and M c W i l l i a m 1967) . P r e - h a r v e s t E f f e c t s — A l t h o u g h t h e main i n t e r e s t i n t h e p r e s e n t s t u d y i s on t h e p o s t - h a r v e s t e f f e c t s o f e l e c t r o -m a g n e t i c r a d i a t i o n , i t s h o u l d be p o i n t e d o u t t h a t t e m p e r a t u r e , l i k e l i g h t , a f f e c t s d i r e c t l y o r i n d i r e c t l y a l l o f a p l a n t ' s p r o c e s s e s d u r i n g growth and d e v e l o p m e n t . The v a r i o u s s t a g e s o f t h e l i f e c y c l e o f a tomato p l a n t ( e . g . g e r m i n a t i o n , v e g e t a t i v e growth and r e p r o d u c t i o n ) a r e a l l dependent upon optimum t e m p e r a t u r e c o n d i t i o n s . Abnormal t e m p e r a t u r e s d u r i n g r e p r o d u c t i o n r e s u l t i n poor f r u i t s e t (Moore and Thomas 19 5 2 ) . Warm n i g h t t e m p e r a t u r e s r e s u l t i n t h e p r o d u c t i o n o f p o o r q u a l i t y tomato f r u i t s (Thompson and K e l l y 1957). F r u i t s e t and d r y m a t t e r p r o d u c t i o n a r e b o t h under t h e r m o p e r i o d i c c o n t r o l i n t h e tomato (Went 1944a, b ) . - 25 -E x p o s u r e o f l o n g d u r a t i o n t o n o n - l e t h a l s u p r a -o p t i m a l t e m p e r a t u r e s s e v e r e l y i n h i b i t s growth p a r t l y due t o t h e i n h i b i t i o n o f c h l o r o p h y l l f o r m a t i o n a t h i g h t e m p e r a t u r e s ( F r i e n d e t a l . 1962). Lomagin and A n t r o p r o v a (1966) a l s o showed t h a t t h e photodynamic i n j u r y o f c h l o r o p h y l l o u s c e l l s r e s u l t s from t h e r m a l damage. The e x p o s u r e t i m e t o cause h e a t i n j u r y d e c r e a s e s l o g a r i t h m i c a l l y as t h e t e m p e r a t u r e r i s e s . H i g h t e m p e r a t u r e s can a l s o l e a d t o d r o u g h t , a s e c o n d a r y h e a t - i n d u c e d i n j u r y ( L e v i t t 1972), due t o t h e e f f e c t o f t e m p e r a t u r e on the r a t e o f m o i s t u r e l o s s ( C u r t i s 1936). P o s t - h a r v e s t E f f e c t s — E x p o s u r e o f d e t a c h e d tomato f r u i t s t o s u p r a - o p t i m a l t e m p e r a t u r e s f o r o v e r 6 h o u r s can s i g n i f i c a n t l y a f f e c t t h e c o l o u r , f i r m n e s s and a c i d c o n t e n t o f t h e f r u i t s ( H a l l 1964a, b ) . The b e s t c o l o u r development was o b t a i n e d between 2 7°C and 3 2°C. F r u i t s h e l d a t 4 2°C o r 4 3°C p r o d u c e d v e r y p o o r c o l o u r . H a l l (19 6 4b found t h a t h i g h t e m p e r a t u r e s i n c r e a s e d t h e a c i d c o n t e n t o f t h e f r u i t s b u t had no e f f e c t on s o l u b l e s o l i d s . T h e r e was a v a r i e t y - t e m p e r a t u r e i n t e r a c t i o n w i t h r e s p e c t t o f i r m n e s s . H i g h t e m p e r a t u r e s above 3 0°C i n h i b i t e d r e d c o l o u r f o r m a t i o n i n t h e tomato (Goodwin and J a m i k o r n 1952, S a y r e e t a l . 195 3) b u t t h e v a r i o u s p i g m e n t s i n v o l v e d i n tomato r i p e n i n g d i f f e r i n t h e i r s e n s i t i v i t y t o h i g h t e m p e r a t u r e s (Tomes 1963). Tomes (1963) found t h a t l y c o p e n e s y n t h e s i s was d r a s t i c a l l y -- 26 -i n h i b i t e d a t 32°C i n a l l s t r a i n s o f tomato p r o d u c i n g t h e p i g m e n t , whereas /S - c a r o t e n e s y n t h e s i s was n o t . I t has been shown t h a t /S - c a r o t e n e s y n t h e s i s c o n t i n u e s above 37°C (Goodwin and J a m i k o r n 1952) and p r o b a b l y up t o 40°C (Vogele 1937). P r o l o n g e d p e r i o d s o f e x p o s u r e t o t e m p e r a t u r e s above 40°C, d e s t r o y p r o t o p l a s m i c s t r e a m i n g and t h e c a r o t e n e p r o d u c i n g mechanism (Vogele 1937). S u n s c a l d The term " s u n s c a l d " i s a p p l i e d t o many t y p e s o f d i s o r d e r d e v e l o p e d upon t h e exposure o f p l a n t p a r t s t o d i r e c t s o l a r r a d i a t i o n . A l t h o u g h t h e r e i s c o n t r o v e r s y as t o the r e l a t i v e c o n t r i b u t i o n by l i g h t o r t e m p e r a t u r e i n t h e development o f t h e d i s o r d e r , t h e r e i s g e n e r a l agreement t h a t i t d e v e l o p s as a r e s u l t o f u n i l a t e r a l e x p o s u r e t o i n t e n s e r a d i a n t energy from t h e s u n . The main v i s i b l e c h a r a c t e r i s t i c o f the d i s o r d e r i s a d e f i n e d a r e a o f d i s c o l o u r e d t i s s u e on t h e s i d e f a c i n g t h e s u n . However, t h e d i s o r d e r v a r i e s from a mere y e l l o w i n g ( L i p t o n 1970) o r b l e a c h i n g ( P a n t a s t i c o e t al_. 1975) o f g r e e n t i s s u e s t o a b l i s t e r e d , p a p e r y ( M c C o l l o c h e t a!L. 1968) sometimes sunken ( R e t i g and Kedar 1967) l e a t h e r y or h a r d p a t c h o f t i s s u e . The v i s u a l symptoms o f s u n s c a l d i n j u r y depend on t h e t y p e o f t i s s u e , t h e age and p h y s i o l o g i c a l m a t u r i t y o f t h e p l a n t p a r t , and t h e i n t e n s i t y and d u r a t i o n o f t h e r a d i a n t energy t o w h i c h t h e t i s s u e was e x p o s e d . The d i v e r s i t y o f - 27 -sunscald symptoms have resulted i n a variety of names such as "greenback","blotchy ripening","solar yellowing","dis-colouration", "sunburn" etc. Sunscald can occur on stems (Huberman 1943),leaves and f r u i t s . It has been observed on many f r u i t s and vegetables including lemons, cabbage, snapbean, pomegranate, pepper and tomato (Pantastico et a l . 1975). Evidence i n the l i t e r a t u r e indicates that sunscald i s enhanced by, and may be mainly caused by, high temperatures. Sayre et a l . (1953) found that d i r e c t exposure of tomato f r u i t s to radiant energy at temperatures above 2 9°C produced ripe f r u i t s of orange or yellow colour instead of red. Venter (1965) observed that f r u i t s shaded with black PVC-foil had a greater occurrence of "greenback" than those shaded with aluminium f o i l during growth. He therefore concluded that greenback was caused by v a r i a t i o n i n the temperature of the f r u i t pericarp during growth and development. It must be pointed out that unbalanced n u t r i t i o n a l l e v e l s , e s p e c i a l l y i n r e l a t i o n to potassium, nitrogen and boron, can also produce similar symptoms (Winsor et a l . 1961, Winsor and Long 1967, Ozbun et_ aJL. 1967) . Lipton (1970) found that while d i s c o l o r a t i o n was greater i n unshaded (and unpainted) f r u i t s than i n f r u i t s painted black, the l a t t e r always had an incidence of about 3 0% scalded f r u i t s whereas white painted and unpainted f r u i t s had none. I t seems, there-fore, that there might be two pathways leading to the development of sunscald i n tomato f r u i t s : one caused by v i s i b l e radiation - 28 -(perhaps enhanced by t e m p e r a t u r e ) l e a d i n g t o d e f e c t i v e c o l o r a t i o n , and t h e o t h e r a t h e r m a l e f f e c t p r o d u c i n g t h e l e a t h e r y a p p e a r a n c e o b s e r v e d i n a f f e c t e d p l a n t p a r t s . R e t i g and Kedar (1967) found t h a t d i r e c t e x p o s u r e o f d e t a c h e d tomato f r u i t s t o s o l a r r a d i a t i o n f o r 30 h o u r s a t a i r t e m p e r a t u r e s o f 26°C t o 29°C, would p r o d u c e " s u n b u r n " whereas e x p o s u r e o f 6 h o u r s would o n l y p r o d u c e " d i s c o l o r a t i o n " on f r u i t s . The l o w e r i n c i d e n c e o f s u n s c a l d i n a t t a c h e d f r u i t s compared w i t h d e t a c h e d f r u i t s i s p r o b a b l y due t o a c o m b i n a t i o n of t h e c o n t i n u o u s t r a n s p o r t system between the f r u i t and t h e p a r e n t p l a n t , f o r g r e a t e r c o n d u c t i v e h e a t t r a n s f e r t h r o u g h t h e enormous p o r e system o f t h e l e a v e s ; t h e r e f l e c t i v e apparatus o f t h e l e a v e s , and t h e g e n e r a l s h a d i n g e f f e c t - o f t h e f o l i a g e s y s t e m . I t i s o f t e n o b s e r v e d t h a t l a r g e f r u i t s have a h i g h e r i n c i d e n c e o f s u n s c a l d t h a n s m a l l o n e s . T h i s was c o n f i r m e d by b o t h V e n t e r (19 65) and L i p t o n (197 0) who showed t h a t f r u i t t e m p e r a t u r e s were h i g h e r i n l a r g e f r u i t s t h a n s m a l l o n e s . T h i s i s p r o b a b l y due t o the h i g h e r h e a t - t r a n s f e r c a p a b i l i t i e s o f t h e s m a l l f r u i t s as a r e s u l t o f t h e i r r e l a t i v e l y g r e a t e r s u r f a c e - t o - v o l u m e r a t i o s . , Harvey (1924) o b s e r v e d t h a t r e d f r u i t s a t t a i n e d c o o l e r t e m p e r a t u r e s t h a n g r e e n f r u i t s and t h a t t h i s was r e s p o n s i b l e f o r t h e absence o f s u n s c a l d i n r e d f r u i t s . However, R e t i g and Kedar (1967) were a b l e t o show t h a t f r u i t t e m p e r a t u r e s a c t u a l l y i n c r e a s e d w i t h r i p e n e s s d u r i n g e x p o s u r e t o r a d i a n t - 29 -e n e r g y . They a l s o found t h a t f r u i t s a t t h e " t u r n i n g " stage d e v e l o p e d s u n s c a l d . I t seems t h a t t h e absence o f d i s c o l o r a t i o n on r e d f r u i t s i s due t o t h e i n a b i l i t y o f h i g h t e m p e r a t u r e s t o d e s t r o y c a r o t e n o i d s once t h e y a r e f o r m e d . The mechanism by w h i c h s t a g e o f r i p e n e s s a f f e c t s the h e a t i n g a b i l i t y o f f r u i t s i s n o t c l e a r . P e r h a p s i t i s due t o v a r i e t a l d i f f e r e n c e s m e d i a t e d t h r o u g h d i f f e r e n c e s i n f r u i t r e f l e c t a n c e ( c u t i c u l a r t h i c k n e s s , waxy l a y e r s e t c . ) as w e l l as t h e p a c k i n g o f t h e ground t i s s u e s and t h e d i s t r i b u t i o n o f s t o m a t a l p o r e s . A l l o f t h e s e f a c t o r s w i l l a f f e c t r a d i a t i o n r e f l e c t a n c e and t r a n s m i t t a n c e as w e l l as c o n v e c t i v e h e a t t r a n s f e r and hence t h e y w i l l i n f l u e n c e f r u i t t e m p e r a t u r e s . I t must be p o i n t e d out t h a t t h e p r e s e n t l e v e l o f knowledge c o n c e r n i n g t h e s p e c i f i c c a u s e s and e f f e c t s o f s u n s c a l d i s p o o r . Much i s known i n a d e s c r i p t i v e sense o f t h e t y p e s o f i n j u r y s u s t a i n e d as a r e s u l t o f e x p o s u r e o f p l a n t t i s s u e s t o i n t e n s e r a d i a n t . e n e r g y o r h i g h t e m p e r a t u r e s . But v e r y l i t t l e e f f o r t has been made t o c h a r a c t e r i s e t h e p r i m a r y f a c t o r s c a u s i n g the s u n s c a l d complex o f i n j u r i e s . A knowledge o f the c a u s a l f a c t o r ( s ) would h e l p i n i n t e r p r e t i n g and c l a s s i f y i n g s u n s c a l d symptoms and would a i d o u r u n d e r s t a n d i n g o f the development o f i n j u r y . A l s o , v e r y l i t t l e work has been done on the q u a l i t y changes w h i c h o c c u r i n f r u i t s i n j u r e d by r a d i a n t e n e r g y . Such i n f o r m a t i o n would h e l p i n e l u c i d a t i n g t h e mechanism by w h i c h t h e i n j u r y d e v e l o p s . - 30 -To p r o v i d e a p e r s p e c t i v e f o r t h e a n a l y s i s o f s u n s c a l d e f f e c t s on tomato f r u i t s t h e f o l l o w i n g s e c t i o n w i l l r e v i e w t h e changes w h i c h n o r m a l l y t a k e p l a c e i n the tomato f r u i t d u r i n g r i p e n i n g . Q u a l i t y Changes i n Tomato F r u i t s D u r i n g R i p e n i n g M a r k e t a c c e p t a b i l i t y o f t h e tomato f r u i t , as w i t h any c r o p commodity, depends upon i t s q u a l i t y . A c c o r d i n g t o Kramer (1965), " q u a l i t y i s t h e c o m p o s i t e o f the c h a r a c t e r i s t i c s t h a t d i f f e r e n t i a t e i n d i v i d u a l u n i t s o f a p r o d u c t and have s i g n i f i c a n c e i n d e t e r m i n i n g t h e degree o f a c c e p t a b i l i t y o f t h a t u n i t by t h e u s e r " . The a t t r i b u t e s o f q u a l i t y w h i c h make t h e tomato f r u i t a c c e p t a b l e t o t h e consumer a r e e x p r e s s e d d u r i n g r i p e n i n g . C o n c e p t s o f R i p e n i n g s T h e r e a r e two main c o n c e p t s o f r i p e n i n g (McGlasson 1970). The f i r s t r e g a r d s r i p e n i n g as a m a n i f e s t a t i o n o f the many changes t h a t t a k e p l a c e i n t h e f r u i t d u r i n g s e n e s c e n c e . As s e n e s c e n c e p r o c e e d s , t h e r e i s a g r a d u a l breakdown o f i n t r a c e l l u l a r o r g a n i z a t i o n . The c o n s e q u e n t random m i x i n g o f enzymes and s u b s t r a t e s r e s u l t s i n v a r i o u s a c t i v i t i e s as pigment d e s t r u c t i o n , d e g r a d a t i o n o f p o l y m e r s ( e . g . s t a r c h and p e c t i c - 31 -s u b s t a n c e s ) , s y n t h e s i s o f new pigments and o t h e r compounds such as e t h y l e n e , f l a v o u r c o n s t i t u e n t s and h i g h energy compounds ( B a i n and M e r c e r 1964, Sacher 1967). The second c o n c e p t c o n s i d e r s r i p e n i n g as t h e f i n a l s t a g e o f d i f f e r e n t i a t i o n which r e q u i r e s t h e s y n t h e s i s o f s p e c i f i c enzymes (Hulme e t a l . 1968, F r e n k e l e t a l . 1968). M c G l a s s o n (1970) p o i n t e d o u t , t h a t i n r e a l i t y b o t h o f t h e c o n c e p t s p r o b a b l y a p p l y . A r e c o n c i l i a t i o n o f the two c o n c e p t s r e f l e c t s t h e view o f P r a t t and G o e s c h l (1969) t h a t r i p e n i n g i s a c o l l e c t i v e term c o v e r i n g many changes i n t h e f r u i t , w h i c h a r e n o t n e c e s s a r i l y c a u s a l l y r e l a t e d t o each o t h e r b u t w h i c h o c c u r more o r l e s s i n p a r a l l e l . A c c o r d i n g t o them, " f r u i t r i p e n i n g i s a s p e c i a l c a s e o f o r g a n s e n e s c e n c e and a l l o f the changes w h i c h o c c u r do n o t r e p r e s e n t d e t e r i o r a t i o n " . R i p e n i n g changes i n tomato f r u i t s l e a d t o t h e e x p r e s s i o n o f t h r e e major q u a l i t y a t t r i b u t e s : c o l o u r , t e x t u r e and f l a v o u r . These a t t r i b u t e s can be examined e i t h e r s u b j e c t i v e l y by human s e n s o r y e v a l u a t i o n o r o b j e c t i v e l y t h r o u g h c h e m i c a l o r p h y s i c a l a n a l y s e s . In t h e l a t t e r c a s e , c o r r e l a t i o n o f such a n a l y s e s w i t h s e n s o r y e v a l u a t i o n o r c h e m i c a l i n d i c a t o r s o f q u a l i t y -must be e s t a b l i s h e d f o r t h e r e s u l t s t o be m e a n i n g f u l . C o l o u r C o l o u r i s u n d o u b t e d l y t h e s i n g l e most i m p o r t a n t q u a l i t y a t t r i b u t e o f t h e ( tomato f r u i t (Gould 1974). I t i s the most - 32 -r e l i a b l e i n d e x o f m a t u r i t y i n t h e tomato (McCollum 1956) and t h e b e s t i n d i c a t o r o f r i p e n e s s i n a l l f r u i t s t h a t undergo c o l o u r changes d u r i n g r i p e n i n g . Tomato f r u i t c o l o u r i s c o n t r o l l e d by genes t h a t f o l l o w M e n d e l i a n i n h e r i t a n c e . The genes i n f l u e n c e f r u i t c o l o u r f o r m a t i o n by c o n t r o l l i n g t h e enzymes a c t i v e i n c a r o t e n o i d b i o - s y n t h e s i s p r o b a b l y by c o n t r o l l i n g t h e c o d i n g o f c h l o r o p l a s t -c h r o m o p l a s t DNA. DNA c o d i n g d i c t a t e s t h e . t y p e o f RNAs w i t h i n t h e c h l o r o p l a s t - c h r o m o p l a s t w h i c h b r i n g about enzyme s y n t h e s i s ( K h u d a i r i 1970) . A t f u l l s i z e m a t u r i t y , t h e tomato f r u i t i s g l o s s y g r e e n due t o t h e p r e s e n c e o f a m i x t u r e o f c h l o r o p h y l l s . I t i s now e s t a b l i s h e d t h a t t h e s e c h l o r o p h y l l s p e r f o r m a d e f i n i t e p h o t o s y n t h e t i c r o l e d u r i n g m a t u r a t i o n (Boe and S a l u n k h e 1967). Two major p r o c e s s e s , c h l o r o p h y l l d e g r a d a t i o n and c a r o t e n o i d s y n t h e s i s , o c c u r d u r i n g tomato r i p e n i n g . The two p r o c e s s e s t a k e p l a c e i n t h e same o r g a n e l l e ( K h u d a i r i 1970), but a n a t o m i c a l and b i o c h e m i c a l s t u d i e s have shown t h a t b o t h p r o c e s s e s o p e r a t e t h r o u g h i n d e p e n d e n t pathways. However, the mechanisms o f b o t h pathways a r e n o t f u l l y u n d e r s t o o d . The c h l o r o p h y l l c o n t e n t o f tomato f r u i t s d e c r e a s e s r a p i d l y d u r i n g t h e t u r n i n g s t a g e ( D a l a i e t a_l. 1965) , w i t h a c o n c o m i t a n t i n c r e a s e i n c h l o r o p h y l l a s e a c t i v i t y (Remirez and Tomes 1964). H o l d e n (1965) p r o v i d e d e v i d e n c e t o show t h a t t h e c h l o r o p h y l l breakdown mechanism i s s e p a r a t e from t h e - 33 -c h l o r o p h y l l a s e - c a t a l y z e d r e a c t i o n . Phan (1972) d i d n o t f i n d an i n c r e a s e i n c h l o r o p h y l l a s e a c t i v i t y d u r i n g tomato r i p e n i n g . K h u d a i r i (1972) has l i s t e d t h e f o l l o w i n g sequence o f u l t r a s t r u c t u r a l changes w h i c h t a k e p l a c e w i t h i n the tomato f r u i t d u r i n g r i p e n i n g . The f i r s t change d u r i n g r i p e n i n g i s t h e l o s s o f t h e g r a n a s t a c k s , f o l l o w e d by d e g r a d a t i o n o f c h l o r o p h y l l s . Then t h e r e i s (a) t h e f o r m a t i o n o f o s m i o p h i l i c g l o b u l e s w h i c h a r e t h e f i r s t c o l o u r e d c a r o t e n o i d s and (b) c o n c u r r e n t a p p e a r a n c e o f t h y l a k o i d s . Grana a l s o b e g i n t o d i s a p p e a r . The d i s a p p e a r a n c e o f t h e g r a n a l e a v e s a s w o l l e n granum compartment w i t h i n w h i c h c a r o t e n o i d s a r e s y n t h e s i z e d . F i n a l l y , t h e r e i s t h e f o r m a t i o n o f e l o n g a t e d r e d c r y s t a l s o f l y c o p e n e ' w h i c h o c c u p y a l a r g e p o r t i o n o f t h e c h r o m o p l a s t . These changes w i t h i n the f r u i t a r e m a n i f e s t e d i n t h e e x t e r n a l c o l o u r changes from mature g r e e n t o t u r n i n g , p i n k and f i n a l l y r e d . The i n t e n s i t y o f t h e r e d c o l o u r i n r i p e n i n g tomatoes depends on t h e c a r o t e n o i d c o n t e n t as w e l l as t h e r e l a t i v e p r o p o r t i o n o f t h e dominant p i g m e n t s (McCollum 1955). The main r e d pigment o f t h e commonly c u l t i v a t e d s p e c i e s o f tomato i s l y c o p e n e . f> - c a r o t e n e i s t h e next major pigment b u t i s f a r l e s s c o n c e n t r a t e d t h a n l y c o p e n e . Tomato f r u i t s a l s o c o n t a i n x a n t h o p h y l l s ( o x y g e n e r a t e d c a r o t e n o i d s ) t o t h e e x t e n t o f about 6% o f t h e t o t a l c a r o t e n o i d c o n t e n t ( C u r l 1961). A l l c a r o t e n o i d s a r e s y n t h e s i z e d from a common p r e c u r s o r , , m e v a l o n i c a c i d . The - 34 -b i o s y n t h e s i s o f c a r o t e n o i d s i s t h e s u b j e c t o f a number o f c o m p r e h e n s i v e r e v i e w s (Goodwin 1965, Goodwin and Goad 1970, K h u d a i r i 1972 and Goodwin 1979). Pigment c o n c e n t r a t i o n i n t h e tomato f r u i t v a r i e s w i t h s p e c i e s , and w i t h i n the same f r u i t t h e r e i s v a r i a t i o n d e p e n d i n g on t h e p o r t i o n o f t h e f r u i t s a m p l e d . McCollum (1955) found t h a t t h e c a r o t e n e c o n t e n t was g r e a t e s t i n t h e p r o x i m a l r e g i o n and was l e a s t i n the d i s t a l o r b l o s s o m - e n d r e g i o n , even though t h e i n i t i a l a p p e a r a n c e o f p i n k c o l o u r o c c u r r e d a t the l a t t e r . The p e r i c a r p a l s o c o n t a i n e d a much g r e a t e r c o n c e n t r a t i o n o f t o t a l c a r o t e n o i d s t h a n t h e l o c u l a r r e g i o n . T e x t u r e No e n t i r e l y s a t i s f a c t o r y d e f i n i t i o n o f " t e x t u r e " , as r e l a t e d t o f o o d q u a l i t y , has y e t been o f f e r e d . De Man (1976) d e f i n e d t e x t u r e as t h e way i n w h i c h t h e s t r u c t u r a l components o f f o o d a r e a r r a n g e d i n m i c r o and macro l e v e l s o f s t r u c t u r e and t h e e x t e r n a l m a n i f e s t a t i o n o f t h i s arrangement and the s e n s o r y s e n s a t i o n s t h a t have been i d e n t i f i e d w i t h q u a l i t y . T e x t u r e i n c l u d e s a wide range o f complex p h y s i c a l c h a r a c t e r i s t i c s . T h i s c o m p l e x i t y has r e s u l t e d i n about 100 d e s c r i p t i v e t e r m s , such as f i r m n e s s , b r i t t l e n e s s , t o u g h n e s s , c r i s p n e s s , e t c . In a d d i t i o n , w e l l - d e f i n e d p h y s i c a l c o n c e p t s s u c h as v i s c o s i t y , e l a s t i c i t y e t c . , have a l s o been i n t r o d u c e d t o d e s c r i b e the c o m p o s i t e q u a l i t i e s known as t e x t u r e (Mohsenin 197 0) . A f u r t h e r a s p e c t i s t h e p e r c e p t i o n o f t e x t u r e i n t h e mouth, as - .'35 -w e l l as t h e sense o f t o u c h , k i n e s t h e t i c p r o p e r t i e s and t h e s e n s a t i o n o f r h e o l o g i c a l p r o p e r t i e s . The t e x t u r e o f f r u i t s and v e g e t a b l e s p a r t l y depends on the r e l a t i v e p r o p o r t i o n s o f the parenchyma, c o l l e n c h y m a and s c l e r e n c h y m a t h e y c o n t a i n . I t a l s o depends on t h e t u r g i d i t y o f t h e i n d i v i d u a l c e l l s , c e l l w a l l t h i c k n e s s , p e r m e a b i l i t y o f t h e plasmalemma, t h e e x t e n t o f t h e i n t e r c e l l u l a r s p a c e s and the s i z e and shape o f t h e c e l l s (Reeve 1970). The t e x t u r a l q u a l i t y o f tomatp f r u i t s i s i n f l u e n c e d by f l e s h " f i r m n e s s " , t h e r a t i o between p e r i c a r p and l o c u l a r t i s s u e and s k i n t o u g h n e s s (Kader e t a l . 1978). " F i r m n e s s " i s t h e most common t e x t u r a l d e s c r i p t i v e t e r m o f tomato f r u i t s . " F i r m n e s s " depends on t h e m i d d l e l a m e l l a and t h e c e l l w a l l and t h e i r r e l a t i v e s t r e n g t h (Bourne 1976). The r e l a t i v e s t r e n g t h o f t h e m i d d l e l a m e l l a and the c e l l w a l l i s due t o t h e p r e s e n c e o f p e c t i n s and c e l l u l o s e ( M i l a d i e t a l . 1969). The o t h e r main c o n s t i t u e n t s o f t h e d r y m a t t e r i n t h e c e l l w a l l s o f tomato f r u i t s , a r e h e m i c e l l u l o s e s and p r o t e i n (Hobson and D a v i e s 1971). In t h e p r i m a r y w a l l , c e l l u l o s e has t h e f u n c t i o n o f g i v i n g some r i g i d i t y - and r e s i s t a n c e t o t e a r i n g w h i l e p e c t i c s u b s t a n c e s and h e m i c e l l u l o s e s c o n f e r p l a s t i c i t y and the a b i l i t y t o s t r e t c h (Van B u r e n 1979). Enzyme A c t i v i t y i n R e l a t i o n t o F i r m n e s s D u r i n g R i p e n i n g - T h e t r a n s f o r m a t i o n o f c e l l w a l l components d u r i n g tomato f r u i t r i p e n i n g i s b r o u g h t about by t h e a c t i o n o f enzymes formed - 36 -w i t h i n t h e c e l l s o f t h e p l a n t d u r i n g growth and development (Gould 1974). Hobson (1963, 1964) found t h a t . p e c t i c s u b s t a n c e s undergo t r a n s f o r m a t i o n and d e g r a d a t i o n by enzymic mechanisms d u r i n g t h e l a t e r s t a g e s o f m a t u r a t i o n and r i p e n i n g , accompanied by an a l m o s t c o m p l e t e l o s s o f t i s s u e c o h e s i o n . O t h e r w o r k e r s (Deshpande e t a l . 1965, Foda 1957, M o g h r a b i 1958, Sayed e t a l . 1966) have a l s o found a c l o s e a s s o c i a t i o n between t h e i n c r e a s i n g s o f t n e s s and changes i n t h e p e c t i c s u b s t a n c e s d u r i n g tomato f r u i t r i p e n i n g . P e c t i c s u b s t a n c e s a r e p o l y ^ g a l a c t u r o n i d e s w i t h n o n -u r o n i d e c a r b o h y d r a t e s c o v a l e n t l y bound t o an u n b r a n c h e d c h a i n o f 1 —> 4 l i n k e d C ( - g a l a c t u r o n i c a c i d u n i t s ( P i l n i k and V o r a g e n 1970). The c a r b o x y l g r o u p s o f t h e g a l a c t u r o n i c a c i d u n i t s ' a r e p a r t l y e s t e r i f i e d w i t h m e t h a n o l and t h e f r e e groups a r e more o r l e s s n e u t r a l i z e d by b a s e s . P e c t i c s u b s t a n c e s a r e g e n e r a l l y c l a s s e d as p r o t o p e c t i n , p e c t i n i c a c i d s , p e c t i n and p e c t i c a c i d s on t h e b a s i s o f t h e m o l e c u l a r w e i g h t , t h e d e g r e e o f m e t h y l e s t e r i f i c a t i o n , and s o l u b i l i t y i n w a t e r . The w a t e r - i n s o l u b l e p e c t i c compounds i n t h e m i d d l e l a m e l l a a r e c a l c i u m and magnesium p e c t a t e s (Bonner 1950). They a c t as i n t e r c e l l u l a r b i n d i n g m a t e r i a l and c o n t r i b u t e l a r g e l y t o t h e f i r m n e s s o f the immature tomato f r u i t . A t t h e same t i m e , t h e y a l l o w some p l a s t i c i t y w h i c h accommodates t h e c h a n g i n g s i z e and shape o f t h e c e l l p r o t o p l a s t s d u r i n g growth (Davies and C o c k i n g 1965). E x t e n s i v e r e v i e w s on t h e c h e m i s t r y o f p e c t i c s u b s t a n c e s have been made by K e r t e s z (1951), Doesburg (1965) and P i l n i k and V o r a g e n (1970). - 37 -R i p e n e s s i n t h e tomato i s accompanied by t h e c o n v e r s i o n o f t h e i n s o l u b l e forms o f p e c t i n i n t o the s o l u b l e forms ( D a l a i e t a l . 1965, LeCrone and Haber 1933, Luh e t a l . 1960). Two main c l a s s e s o f enzymes: p o l y g a l a c t u r o n a s e (or p e c t i n a s e ) and p e c t i n e s t e r a s e (or p e c t a s e ) , a r e r e s p o n s i b l e f o r t h e t r a n s f o r m a t i o n o f p e c t i c s u b s t a n c e s . P o l y g a l a c t u r o n a s e d e p o l y m e r i s e t h e l o n g p e c t i c c h a i n s w h i l e p e c t i n e s t e r a s e removes t h e m e t h y l e s t e r g r o u p s from t h e m o l e c u l e . V a r i o u s r e s e a r c h e r s have found t h a t tomato f r u i t s c o n t a i n t h e enzymes ' p e c t i n e s t e r a s e ( H i l l s and M o t t e r n 1947, Lee e t a l . 1968, Hobson 1963), p o l y g a l a c t u r o n a s e (McCready e t a l . 1955, Hobson 1962, Reymond and P h a f f 1965) and - g a l a c t o s i d a s e ( W a l l n e r and Walker 1975). C e l l u l a s e a c t i v i t y has a l s o been o b s e r v e d t o i n c r e a s e d u r i n g r i p e n i n g i n tomatoes ( H a l l 1963). However, Hobson (1968) found no c o r r e l a t i o n between c e l l u l a s e a c t i v i t y and s o f t e n i n g i n t o m a t o . S i m i l a r l y y G r o s s and W a l l n e r (1979) found t h a t t h e d e c l i n e i n g a l a c t o s e and a r a b i n o s e c o n t e n t d u r i n g tomato r i p e n i n g was n o t due t o - g a l a c t o s i d a s e . They a l s o showed t h a t t h e l o s s o f t h e s e n e u t r a l s u g a r s , w a s s e p a r a t e f r o m , a n d i n d e p e n d e n t o f , p o l y u r o n i d e s o l u b i l i z a t i o n . A t the moment, t h e o n l y c e l l w a l l change t h a t i s c l e a r l y r e l a t e d t o f r u i t s o f t e n i n g i s t h e h y d r o l y s i s o f QC - 1 , 4 - g a l a c t u r o n o s y l l i n k a g e s by p o l y g a l a c t u r o n a s e (Gross and W a l l n e r 1979). - 38 -C h e m i c a l C o n s t i t u e n t s A l a r g e number o f c o m p o s i ' t i o n a l s t u d i e s have been c a r r i e d o u t on tomato f r u i t s (Winsor e t a_l. 19 62a, b , D a v i e s and W i n s o r 1969, D a v i e s 1965, D a l a i e t E Q . 1965, Yu e t a l . 1967). A l l showed t h a t t h e major c h e m i c a l c o n s t i t u e n t s o f n u t r i t i o n a l i m p o r t a n c e i n t h e tomato a r e s t a r c h , s u g a r , a s c o r b i c a c i d , o r g a n i c a c i d s ( e . g . c i t r i c and m a l i c a c i d s ) , p r o t e i n s and some amino a c i d s ( e . g . g l u t a m i c and a s p a r t i c a c i d s ) . S t a r c h c o n c e n t r a t i o n d e c r e a s e s t h r o u g h o u t tomato r i p e n i n g . The s o l u b l e c a r b o h y d r a t e s o f tomatoes a r e a l m o s t e n t i r e l y r e d u c i n g s u g a r s (Hobson and D a v i e s 1971) and t h e y c o n s t i t u t e about 1.5-4.5% o f f r e s h w e i g h t (Winsor 1966). The s u g a r c o n t e n t o f t h e tomato i n c r e a s e s p r o g r e s s i v e l y t h r o u g h o u t m a t u r a t i o n up t o t h e m a t u r e - g r e e n s t a g e . I t i n c r e a s e s s h a r p l y a t the t u r n i n g s t a g e and d e c l i n e s d u r i n g the l a t e r s t a g e s o f r i p e n i n g i n s t o r a g e . S t e v e n s (1974) r e p o r t e d t h a t t h e tomato r a n k s t h i r d among f r u i t s and v e g e t a b l e s as a d i e t a r y s o u r c e o f v i t a m i n C i n the U n i t e d S t a t e s because o f t h e l a r g e volume o f f r u i t consumed. Whole r e d - r i p e tomatoes c o n t a i n n e a r l y a l l t h e i r v i t a m i n C i n the r e d u c e d form (Gould 1974). The a s c o r b i c a c i d c o n t e n t i n tomato a v e r a g e s 25 mg p e r 100 g f r e s h w e i g h t ( O l l i v e r 1967). Thus an a v e r a g e s i z e f r u i t s u p p l i e s about 40% o f an a d u l t ' s o r 60% o f a c h i l d ' s , U n i t e d S t a t e s recommended d a i l y a l l o w a n c e o f v i t a m i n C. - 39 -Data c o n c e r n i n g t h e s t a b i l i t y o f a s c o r b i c a c i d c o n t e n t d u r i n g tomato r i p e n i n g a r e i n c o n s i s t e n t . Some i n v e s t i g a t o r s r e p o r t e d l i t t l e change (Clow and M a r l a t t 1930, K a s k i e t a_l. 1944 , Wokes and Organ 1943), w h i l e o t h e r s f o u n d d i f f e r e n t l e v e l s d e p e n d i n g on t h e i r r i p e n e s s b e f o r e h a r v e s t ( S c o t t and Kramer 1949, P a n t o s and M a r k a k i s 1973). F r y e r e t a l . (1954) found t h a t t h e r e was an i n c r e a s e i n a s c o r b i c a c i d c o n c e n t r a t i o n d u r i n g the p e r i o d from m a t u r a t i o n t o the l a s t s t a g e s o f r i p e n e s s . On t h e c o n t r a r y , o t h e r w o r k e r s found t h a t t h e i n i t i a l i n c r e a s e was f o l l o w e d by a s l i g h t d e c r e a s e d u r i n g t h e f i n a l s t a g e s o f r i p e n i n g ( D a l a i e t a_l. 196 5, M a l e w s k i and, M a r k a k i s 1971). T h i s i n c o n s i s t e n c y i s p r o b a b l y due t o v a r i e t a l d i f f e r e n c e s (Stevens e t a l . 1974) and d i f f e r e n t m e t h o d o l o g i e s . The a s c o r b i c a c i d c o n t e n t o f r i p e tomato f r u i t s v a r i e s d e p e n d i n g on t h e s t a g e o f r i p e n e s s b e f o r e h a r v e s t (Pantos and M a r k a k i s ) , s e a s o n a l i t y , g r o w i n g c o n d i t i o n and s h a d i n g (Boe and Salunkhe 1957, B i s o g n i e t a l . 1976). The p r e d o m i n a n t o r g a n i c a c i d s i n tomatoes a r e c i t r i c and m a l i c a c i d s (Hobson and D a v i e s 1971). O t h e r a c i d s o c c u r i n • t r a c e s and t h e y i n c l u d e f o r m i c , a c e t i c , l a c t i c , f u m a r i c and a l p h a o x o - a c i d s ( 0( - o x o g l u t a r i c a c i d , p y r u v i c a c i d and d i h y d r o x y t a r t a r i c a c i d ) . T i t r a t a b l e a c i d i t y i n t h e tomato f r u i t i n c r e a s e s i n i t i a l l y and r e a c h e s a maximum v a l u e a t a p p r o x i m a t e l y the t i m e o f f i r s t a p p e a r a n c e o f p i n k c o l o u r a t t h e b r e a k e r s t a g e . T h e r e a f t e r , a c i d i t y d e c r e a s e s p r o g r e s s i v e l y (Winsor e t a l . 1962b) Changes i n t i t r a t a b l e a c i d i t y o f t h e tomato can be a t t r i b u t e d t o changes i n c i t r i c a c i d a l o n e ( B r a d l e y 1962) o r b o t h c i t r i c and m a l i c a c i d s (Davies 1964). - 40 -pH i s i n v e r s e l y r e l a t e d t o t i t r a t a b l e a c i d i t y . K o s k i t a l o (1970) found t h a t pH i n tomatoes i n c r e a s e d u n i f o r m l y as t i t r a t a b l e a c i d i t y d e c r e a s e d d u r i n g r i p e n i n g . The pH o f tomato f r u i t s i n c r e a s e w i t h l a t e r t i m e o f h a r v e s t (Hanna 1961, Yamaguchi e t a l . 1 9 6 0 ) a n d a l s o w i t h i n c r e a s i n g t e m p e r a t u r e s d u r i n g t h e g r o w i n g s e a s o n ( K o s k i t a l o 1970) . The C l i m a c t e r i c , E t h y l e n e P r o d u c t i o n and T h e i r  R e l a t i o n s h i p t o R i p e n i n g i n Tomato F r u i t s The term " c l i m a c t e r i c " r e f e r s t o a p e r i o d i n the ontogeny o f c e r t a i n f r u i t s d u r i n g w h i c h , c o n c u r r e n t w i t h a s e r i e s o f b i o c h e m i c a l and b i o p h y s i c a l c h a n g e s , t h e r e i s an u p s u r g e i n c a r b o n d i o x i d e p r o d u c t i o n from a minimum t o a maximum and t h e n a d e c l i n e . The term r e s p i r a t o r y c l i m a c t e r i c d a t e s back t o 1922 when K i d d and West (Rhodes 1970), m e a s u r i n g t h e r e s p i r a t o r y a c t i v i t y o f "Bramley" s e e d l i n g apples,, found t h a t a f t e r p i c k i n g , the r a t e o f c a r b o n d i o x i d e p r o d u c t i o n o f the f r u i t f e l l t o a minimum v a l u e , t h e n r o s e r a p i d l y t o a peak and s u b s e q u e n t l y d e c l i n e d . F r u i t s p o s s e s s i n g t h i s c h a r a c t e r i s t i c a r e termed " c l i m a c t e r i c " w h i l e t h o s e t h a t do n o t a r e c a l l e d " n o n - c l i m a c t e r i c " f r u i t s ( B i a l e 1 9 6 0 ) . G u s t a f s o n (1929) was t h e f i r s t t o show t h a t t h e tomato e x h i b i t s t h e c l i m a c t e r i c r i s e i n r e s p i r a t i o n . - 41 -E t h y l e n e p r o d u c t i o n a l s o u s u a l l y f o l l o w s the r e s p i r a t o r y p a t t e r n . Workman and P r a t t (1957) found t h a t t h e p a t t e r n o f e t h y l e n e p r o d u c t i o n o f tomato f r u i t s was a s i g m o i d c u r v e . M e a s u r a b l e q u a n t i t i e s o f e t h y l e n e began t o a c c u m u l a t e w i t h t h e f i r s t a p p e a r a n c e o f p i n k c o l o u r a t about t h e o n s e t o f t h e r i s e i n r e s p i r a t i o n r a t e , and e t h y l e n e r e l e a s e r e a c h e d a maximum r a t e n e a r t h e end o f t h e s t o r a g e l i f e o f t h e f r u i t . In t h e 1950s and e a r l y 60s, t h e r o l e o f e t h y l e n e i n r i p e n i n g c o n s t i t u t e d an a r e a o f much c o n t r o v e r s y i n p o s t - h a r v e s t p h y s i o l o g y . C r o k e r and h i s c o w o r k e r s a t t h e Boyce Thompson I n s t i t u t e had s u g g e s t e d i n 1935 t h a t e t h y l e n e was a r i p e n i n g hormone. But B i a l e and c o w o r k e r s o b t a i n e d d a t a from a s e r i e s o f e x p e r i m e n t s t o show t h a t e t h y l e n e i s a b y - p r o d u c t o f r i p e n i n g . Subsequent s t u d i e s i n v o l v i n g b e t t e r methodology p r o d u c e d r e s u l t s w h i c h t e n d e d t o f a v o u r t h e e s s e n t i a l i t y o f e t h y l e n e as a r i p e n i n g hormone (Burg and Burg 1962, 1965, Mapson and R o b i n s o n 1960, S c o t t e t a_l. 1970). However, r e c e n t e v i d e n c e from s t u d i e s on tomatoes has shown t h a t e t h y l e n e i s n o t an " e f f e c t u a t o r " o f r i p e n i n g b u t t h a t i n c r e a s e d e t h y l e n e p r o d u c t i o n i s an i n t e g r a l p a r t o f t h e r i p e n i n g p r o c e s s ( S t e n v e r s and B r u i n s m a 1975, M c G l a s s o n e t a l . 1975). O t h e r c h e m i c a l s , i n c l u d i n g p r o p y l e n e , e t h a n e and p r o p a n e , have a l s o been found t o p r o d u c e the same e f f e c t as e t h y l e n e on tomato m i t o c h o n d r i a (Mehard 1 9 6 9 ) . R e c e n t l y , i t was a l s o s u g g e s t e d t h a t c a r b o n monoxide m i g h t i n i t i a t e t h e a u t o -- 42 -c a t a l y t i c f o r m a t i o n o f e t h y l e n e d u r i n g r i p e n i n g . G l a d o n and S t a b y (1979) found t h a t a l t h o u g h c a r b o n monoxide was p r o d u c e d i n t h e i n t e r n a l atmosphere o f tomato f r u i t s a t a l l s t a g e s of r i p e n i n g , the c o n c e n t r a t i o n had an i r r e g u l a r t i m e c o u r s e and t h e r e was i n s u f f i c i e n t q u a n t i t y t o e l i c i t t h e t y p i c a l e t h y l e n e r e s p o n s e s . The r o l e and mechanism o f e t h y l e n e i n f r u i t r i p e n i n g i s d e a l t w i t h i n s e v e r a l r e v i e w a r t i c l e s by Burg (1962), Lyons (1962), P r a t t and G o e s c h l (1969), L i e b e r m a n (1979) and t h e t r e a t i s e by M c G l a s s o n (1970). A l l r i p e n e s s c h a n g e s , such as c o l o u r , t e x t u r e and f l a v o u r , have been found t o accompany o r become more p r o n o u n c e d d u r i n g t h e r e s p i r a t o r y c l i m a c t e r i c and t h e p e r i o d o f peak e t h y l e n e p r o d u c t i o n . However, i t has been shown by some w o r k e r s t h a t t h e c l i m a c t e r i c i n c r e a s e i n r e s p i r a t i o n i s n o t dependent upon r i p e n i n g . F o r example, D o s t a l and L e o p o l d (19 67) were a b l e t o s e p a r a t e t h e c l i m a c t e r i c r i s e from t h e c o l o u r changes a s s o c i a t e d w i t h r i p e n i n g i n tomato f r u i t s . They found t h a t g i b b e r e l l i c a c i d had no e f f e c t on t h e c l i m a c t e r i c r i s e but m a r k e d l y r e t a r d e d c o l o u r c h a n g e s . The mode o f a c t i o n o f g i b b e r e l l i c a c i d as a r i p e n i n g r e t a r d a n t i s , h o w e v e r , n o t known. S i m i l a r l y , F r e n k e l e t a l . (1968) found t h a t c y c l o h e x i m i d e , a p r o t e i n s y n t h e s i s i n h i b i t o r , i n h i b i t e d b o t h r i p e n i n g and e t h y l e n e s y n t h e s i s whereas r e s p i r a t i o n r a t e was u n a f f e c t e d . I t must be p o i n t e d o u t , however, t h a t i n a l l t h e s t u d i e s r e p o r t e d , i n t h e l i t e r a t u r e on c l i m a c t e r i c f r u i t s , - 43 -t h e q u a l i t y changes a s s o c i a t e d w i t h r i p e n i n g d i d not o c c u r w i t h o u t t h e t y p i c a l r i s e i n r e s p i r a t i o n . The o c c u r r e n c e o f t h e c l i m a c t e r i c w i t h o u t t h e c o n c o m i t a n t changes i n r i p e n e s s and e t h y l e n e p r o d u c t i o n i n t h e p r e s e n c e o f c y c l o h e x i m i d e , m i g h t be due t o t h e c o n c e n t r a t i o n o f c y c l o h e x i m i d e w h i c h i n i t s e l f can u n c o u p l e o x i d a t i o n and p h o s p h o r y l a t i o n ( E l l i s and MacDonald 1969). Basham (1965) emphasized t h a t e t h y l e n e p r o d u c t i o n and r e s p i r a t i o n r a t e s were c l o s e l y c o r r e l a t e d o n l y up t o t h e o n s e t o f t h e c l i m a c t e r i c r i s e . But t h e r e l a t i o n between e t h y l e n e p r o d u c t i o n and r e d c o l o u r f o r m a t i o n w h i c h o c c u r s i n the p o s t -c l i m a c t e r i c p e r i o d i n tomato was a c o n t i n u i n g o n e , b o t h h a v i n g the same t e m p e r a t u r e c o e f f i c i e n t s . E t h y l e n e P r o d u c t i o n Under S t r e s s C o n d i t i o n s E t h y l e n e p r o d u c t i o n by p l a n t t i s s u e s i s g e n e r a l l y s t i m u l a t e d by s t r e s s c o n d i t i o n s such as m e c h a n i c a l i n j u r y , c h i l l i n g , f r e e z i n g , water s t r e s s , n o x i o u s c h e m i c a l s , i r r a d i a t i o n , and damage from i n s e c t s and d i s e a s e s ( L i e b e r m a n 1979, M c G l a s s o n 1970, P r a t t and G o e s c h l 1969). The amount o f e t h y l e n e p r o d u c e d by s t r e s s e d t i s s u e s depends upon t h e magnitude o f i n j u r y c a u s e d by t h e s t r e s s ( B r e s s a n e t a l . 1979, E l s t n e r and Konze 1976) . However, s t r e s s e t h y l e n e i s a p r o d u c t o f l i v i n g t i s s u e s . I t c e a s e s when a damage i s extreme enough t o k i l l t h e t i s s u e (Abeles 1973). The mechanism by w h i c h s t r e s s e d t i s s u e s p r o d u c e e t h y l e n e i s n o t known. L i e b e r m a n (197 9) s u g g e s t e d s t r e s s e d t i s s u e s a r e e i t h e r i n c a p a b l e o f m e t a b o l i z i n g - 44 -ethylene or that t h e i r metabolism of ethylene i s severely reduced. The physiological role of stress ethylene i s also not known (Lieberman 1979), but i t has been associated with defence mechanisms and disease resistance (Stahmann et aJL. 1966) . The o r i g i n of ethylene i n stressed tissues i s considered to be sim i l a r to that of the unstressed tissues. It i s probably derived from the same precursor, methionine (Abeles and Abeles 1972, Hanson and Kende 1976, Hyodo 1977, Mapson et a l . 1970) . - 45 -MATERIALS AND METHODS P l a n t M a t e r i a l : H a r v e s t i n g and P r e - t r e a t m e n t H a n d l i n g Tomato ( L y c o p e r s i c o n e s c u l e n t u m M i l l . ) f r u i t s used i n t h i s s t u d y were grown i n g r e e n h o u s e s a t S e t o Farms, 17453 - 8th Avenue, S u r r e y , B . C . o r a t Magnum P r o d u c t s L t d . , 15860 - 2 4th Avenue, White Rock, B . C . B o t h g r e e n h o u s e s grew the c u l t i v a r V e n d o r . In a l l e x p e r i m e n t s , I p e r s o n a l l y h a n d -h a r v e s t e d t h e f r u i t s , s e l e c t i n g them f o r s i z e , shape and m a t u r i t y . O n l y f r u i t s from t r u s s e s t h a t were a p p r o x i m a t e l y 100-150 cm above t h e ground were p i c k e d . H a r v e s t e d f r u i t s were t h e n q u i c k l y t r a n s p o r t e d i n s t a n d a r d tomato c r a t e s t o U . B . C . As soon as t h e f r u i t s a r r i v e d i n the l a b o r a t o r y , t h e y were f u r t h e r s e l e c t e d f o r u n i f o r m s i z e and shape and s u b d i v i d e d i n t o r i p e n e s s c l a s s e s , whenever a p p l i c a b l e , b e f o r e t r e a t m e n t . The p e r i o d between p i c k i n g and t h e b e g i n n i n g o f t r e a t m e n t was n e v e r more t h a n 2 h o u r s . T r e a t m e n t Chamber D e s i g n and C o n s t r u c t i o n F i e l d o b s e r v a t i o n s and r e p o r t s i n the l i t e r a t u r e i n d i c a t e d t h a t " h i g h l i g h t i n t e n s i t y " a n d / o r h i g h t e m p e r a t u r e s were p r o b a b l y t h e p r i n c i p a l f a c t o r s c a u s i n g S u n s c a l d and s i m i l a r s u n - m e d i a t e d i n j u r i e s o f t o m a t o e s . T r e a t m e n t chambers ( F i g . 1) were t h e r e f o r e d e s i g n e d and c o n s t r u c t e d t o p e r m i t s e p a r a t e o r s i m u l t a n e o u s d e t e r m i n a t i o n o f t h e e f f e c t s o f d i f f e r e n t l e v e l s ~ 46 -F i g u r e 1. D i a g r a m o f t h e T r e a t m e n t Chamber u s e d t o i r r a d i a t e tomato f r u i t s showing t h e E x t e r n a l View (A) and t h e C r o s s - s e c t i o n a l View ( B ) . L e g e n d : a Cap b Body o f chamber c I n n e r C o p p e r t u b i n g d Aluminum f o i l l i n i n g e E x t e r n a l C o p p e r t u b i n g f T h e r m o c o u p l e ( a i r t e m p e r a t u r e ) g T h e r m o c o u p l e ( F r u i t t e m p e r a t u r e ) h D i a l Thermometer i T h e r m i s t o r j Tomato F r u i t k The Base 1 F a n m H e a t i n g E l e m e n t p Lamps A r r o w s i n d i c a t e t h e d i r e c t i o n o f c o l d w a t e r c i r c u l a t i o n . - 47 -- 48 -o f t e m p e r a t u r e and r a d i a n t f l u x d e n s i t y on tomato f r u i t s . F o u r s i m i l a r chambers were u s e d ; One chamber s e r v e d as the c o n t r o l w h i l e t h e r e m a i n i n g t h r e e were used as d e s i r e d t o p r o d u c e d i f f e r e n t l e v e l s o f t e m p e r a t u r e and r a d i a n t f l u x d e n s i t y . E a c h chamber c o n s i s t e d o f t h r e e p a r t s : the main u n i t o r t h e Body, and two s u b - u n i t s , t h e Base and the Cap. The Body was a m e t a l b a r r e l 39 cm l o n g by 27 cm o u t e r d i a m e t e r , c u t open on b o t h ends l e a v i n g a f l a n g e 1 cm wide p r o t r u d i n g i n w a r d s . A 4..5 meter l o n g c o p p e r t u b i n g (6 mm O . D . ) was c o i l e d and a l i g n e d i n s i d e a l o n g t h e a x i s o f t h e b a r r e l . The e n t i r e i n n e r s u r f a c e o f t h e b a r r e l i n c l u d i n g t h e c o p p e r c o i l s , was c o v e r e d w i t h a l a y e r o f aluminum f o i l . A n o t h e r t u b i n g o f 8 mm O . D . was wound s i x t i m e s a r o u n d t h e o u t e r c i r c u m f e r e n c e o f t h e b a r r e l . The o u t e r t u b i n g was s o l d e r e d t o the b a r r e l a l o n g i t s e n t i r e l e n g t h t o e n s u r e good c o n t a c t and hence good h e a t exchange. B o t h t u b i n g s c a r r i e d w a t e r t h a t i n i t i a l l y had been c o o l e d to l e s s t h a n 6°C by c i r c u l a t i n g i t w i t h pumps t h r o u g h a r e f r i g e r a t e d w a t e r - b a t h c o n t r o l l e d by a M i c r o t r o l C o n s t a n t Flow C o n t r o l l i n g T h e r m o s t a t (Blue M E l e c t r i c C o . U . S . A . ) . A r i n g - s h a p e d r u b b e r g a s k e t was g l u e d w i t h s i l i c o n e r u b b e r t o each p r o t r u d i n g m e t a l f l a n g e on t h e b a r r e l t o e n s u r e an a i r - t i g h t f i t t i n g o f t h e Base and t h e Cap. 1 The Base was made o f P l e x i g l a s . I t c o n s i s t e d o f two c i r c u l a r d i s c s , t h e Te mplate and t h e Base p r o p e r , e a c h 6.4 mm t h i c k b u t 24 cm and 26.5 cm d i a m e t e r , r e s p e c t i v e l y . The T e m p l a t e w h i c h was p e r f o r a t e d w i t h 5 mm d i a m e t e r h o l e s a t 0.5 cm - 49 -i n t e r v a l s , was mounted onto t h e Base p r o p e r by means o f 12 cm x 2.5 cm x 1.25 cm s t u d s . The Base was s e c u r e d t o t h e Body d u r i n g t r e a t m e n t by f o u r s e t s o f s u i t c a s e l o c k s . The Cap was a 4 mm t h i c k p l a i n g l a s s s h e e t . An a i r - t i g h t s e a l between t h e Cap and t h e Body was m a i n t a i n e d by s i l i c o n e g r e a s e a p p l i e d t o the edge o f t h e chamber. In t h e h i g h t e m p e r a t u r e e x p e r i m e n t s , t h e r e was no cap s i n c e t h e h e a t e r w h i c h w i l l be d e s c r i b e d s h o r t l y , a l s o s e r v e d as the c a p . Measurement and C o n t r o l o f I r r a d i a n c e F o r t h e l i g h t e x p e r i m e n t s , t h e Base was a l s o p r o v i d e d w i t h a r i n g - s h a p e d h e a t i n g e l e m e n t mounted on i n s u l a t o r s on the lower d i s c (Base p r o p e r ) . A i r c i r c u l a t i o n w i t h i n t h e chamber was p r o v i d e d by a f a n a f f i x e d t o the c e n t r e o f t h e l o w e r d i s c o f t h e B a s e . Mounted above each chamber e x c e p t f o r t h e c o n t r o l were t h r e e 3 00 W PAR 56/2 MFL medium f l o o d , c o o l l u x S y l v a n i a i n c a n d e s c e n t lamps ( S y l v a n i a E l e c t r i c P r o d u c t s I n c . , D e n v e r , M a s s . , U . S . A . ) . The lamps were suspended from a p u l l e y ( F i g . 1 ) , and d e s i r e d i r r a d i a n c e s were o b t a i n e d by v a r y i n g the lamp d i s t a n c e as w e l l as by l a y e r i n g cheese c l o t h o n t o t h e Cap. The c h e e s e c l o t h p l u s t h e aluminum f o i l l i n i n g p r o v i d e d a more u n i f o r m r a d i a t i o n e n v i r o n m e n t w i t h i n t h e chamber. - 50 -The i r r a d i a n c e a t t h e f r u i t s u r f a c e was measured w i t h K e t t e r i n g r a d i o m e t e r ( Y e l l o w S p r i n g I n s t r u m e n t s C o . ) . S p e c t r a l energy d i s t r i b u t i o n s were d e t e r m i n e d u s i n g an ISCO Model SR s p e c t r o r a d i o m e t e r ( I n s t r u m e n t a t i o n S p e c i a l t i e s C o . ) w h i c h was r e c a l i b r a t e d b e f o r e t h i s r e s e a r c h was done (see A p p e n d i x ) . Measurement and C o n t r o l o f T e m p e r a t u r e F o r t h e h i g h t e m p e r a t u r e e x p e r i m e n t s , a s u b - u n i t s i m i l a r t o the Base d e s c r i b e d above f o r l i g h t e x p e r i m e n t s , was c o n s t r u c t e d and s e r v e d as t h e H e a t e r . I t was s i m p l y i n v e r t e d and p l a c e d on t o p o f t h e Body o f t h e chamber, r e p l a c i n g t h e Cap. T h i s e n s u r e d a s i m i l a r geometry o f t r e a t m e n t i n b o t h the t e m p e r a t u r e and l i g h t e x p e r i m e n t s . The Base i n t h e h i g h t e m p e r a t u r e e x p e r i m e n t s had n e i t h e r a h e a t i n g element nor a f a n . A i r c i r c u l a t i o n was t h e r e f o r e from above t h e f r u i t s i n s t e a d o f from below as i n t h e l i g h t e x p e r i m e n t s . D e s i r e d t e m p e r a t u r e w i t h i n each chamber was a c h i e v e d by v a r y i n g t h e f l o w r a t e o f t h e c o l d water c i r c u l a t e d t h r o u g h t h e c o p p e r t u b i n g s . In a d d i t i o n , t h e h e a t i n g e l e m e n t s i n b o t h t h e t e m p e r a t u r e and l i g h t e x p e r i m e n t s were c o n n e c t e d t o a t h e r m o s t a t . In each chamber, a t t h e l e v e l o f the f r u i t s , was a t h e r m i s t o r c o n n e c t e d t o t h e t h e r m o s t a t . A d i a l t y p e thermometer (Model 2261 Western I n s t r u m e n t s I n c . , Newark, N . J . , - 51 -U . S . A . ) was i n s e r t e d i n t o t h e chamber 15 cm above the Base t o i n d i c a t e t h e a p p r o x i m a t e a i r t e m p e r a t u r e w i t h i n the chamber a t t h e f r u i t l e v e l . More a c c u r a t e measurements o f chamber a i r t e m p e r a t u r e a t f r u i t l e v e l were o b t a i n e d u s i n g c o p p e r - c o n s t a n t a n t h e r m o c o u p l e s c o n n e c t e d t o a Comark e l e c t r o n i c thermometer t y p e 1624. F r u i t t e m p e r a t u r e s were measured by i n s e r t i n g t h e r m o -c o u p l e s s k i n deep i n t o t h e f r u i t a t t h e s t y l a r s c a r . Measurements o f t e m p e r a t u r e s w i t h i n f r u i t s a t depths 0 ( s k i n l e v e l ) , 1, 2, 3 and 4 cm were made by a t t a c h i n g t h e r m o c o u p l e s t o t h e drawn end o f a 3 mm t h i c k g l a s s r o d a t 1 cm i n t e r v a l s . A 20 p o i n t S e l e c t o r u n i t a t t a c h e d t o t h e Comark Thermometer p e r m i t t e d t e m p e r a t u r e s o f s e v e r a l f r u i t s t o be measured d u r i n g an e x p e r i m e n t w i t h o u t d i s t u r b i n g t h e f r u i t s o r t h e r m o c o u p l e s . V i s u a l R a t i n g Schemes ( i) R i p e n e s s A s i m p l e v i s u a l r i p e n e s s r a t i n g scheme was d e v e l o p e d by m o d i f y i n g t h e c l a s s i f i c a t i o n methods o f Abder-Kader e t a l . (1968) and W o r t h i n g t o n (1974). I n d i v i d u a l f r u i t s were s c o r e d on a s c a l e o f 0 f o r m a t u r e - g r e e n t o 6 f o r o v e r - r i p e ( i . e . f u l l r e d but s o f t t o m a t o ) ( T a b l e 1 ) . T a b l e 1. R i p e n e s s S c o r e A V i s u a l R a t i n g Scheme f o r A s s e s s i n g the R i p e n e s s o f Tomato F r u i t s . C l a s s D e s c r i p t i o n 0 Mature g r e e n 1 B r e a k e r 2 T u r n i n g (Advanced b r e a k e r ) 3 P i n k 4 P i n k - r e d 5 Red 6 O v e r - r i p e E n t i r e l y g l o s s y g r e e n i n c o l o r F i r s t appearance o f e x t e r n a l l i g h t p i n k c o l o r F r u i t s are s t i l l >^ 60% g r e e n L e s s than about 50% g r e e n , c o n c e n t r a t i n g m a i n l y a t t h e c a l y x end No g r e e n c o l o r , n e a r t a b l e - r i p e F i r m - r i p e ; d e s i r a b l e t a b l e - r i p e n e s s t o c a n n i n g - r i p e n e s s I n t e n s e r e d c o l o r ; A c c e p t a b l e c a n n i n g r i p e n e s s ; F r u i t no l o n g e r f i r m b u t s o f t - 53 -( i i ) I n j u r y F i e l d o b s e r v a t i o n and p r e l i m i n a r y e x p e r i m e n t s r e v e a l e d v a r y i n g d e g r e e s o f i n j u r y development d e p e n d i n g on f r u i t r i p e n e s s and d u r a t i o n o f e x p o s u r e . A r a t i n g scheme was t h e r e f o r e d e v e l o p e d t o p e r m i t a q u i c k v i s u a l e v a l u a t i o n o f t h e s e v e r i t y o f i n j u r y . T a b l e 2 shows t h e d e s c r i p t i o n o f each s c o r e . In a l l c a s e s where v i s u a l r a t i n g schemes were employed i n t h i s s t u d y , f r u i t s were p e r s o n a l l y s c o r e d f o r r i p e n e s s or i n j u r y under f u l l l a b o r a t o r y l i g h t i n g c o n d i t i o n s a t the same l o c a t i o n e v e r y t i m e t o m i n i m i s e v a r i a b i l i t y due t o o b s e r v e r o r l o c a t i o n . C h a r a c t e r i z a t i o n o f C a u s a l F a c t o r s E n v i r o n m e n t and D u r a t i o n o f E x p o s u r e P r e l i m i n a r y t r i a l s were c a r r i e d o u t t o d e t e r m i n e the e f f e c t o f some e n v i r o n m e n t a l c o n d i t i o n s and d u r a t i o n o f t r e a t m e n t on t h e development o f i n j u r y on tomato f r u i t s . F r u i t s were h a r v e s t e d a t t h e m a t u r e - g r e e n s t a g e and d i v i d e d i n t o b a t c h e s o f t e n . Some f r u i t s were p l a c e d on b e n c h e s , s t y l a r ends u p , e i t h e r i n t h e greenhouse o r i n o u t s i d e open a i r . O t h e r f r u i t s were e n c a s e d i n c y l i n d r i c a l g l a s s t u b e s 30 cm by 10 cm (O.D.) and p l a c e d on benches i n t h e open a i r , o r i e n t e d T a b l e 2. A V i s u a l R a t i n g Scheme f o r I n j u r y Assessment i n R a d i a n t Energy -T r e a t e d Detached Tomato F r u i t s . S c o r e D e s i g n a t i o n D e s c r i p t i o n No A p p a r e n t I n j u r y I n c i p i e n t I n j u r y I n t e r m e d i a t e I n j u r y Advanced I n j u r y S e m i - t o t a l I n j u r y T o t a l I n j u r y F r u i t s a r e not v i s u a l l y d i f f e r e n t from t h e u n t r e a t e d c o n t r o l a t the same s t a g e o f r i p e n e s s . A f a i n t but n o t i c e a b l e change i n s k i n c o l o r . U n d e r l y i n g t i s s u e s and r i d g e s d e m a r c a t i n g t h e l o c u l i show up i n a v i s i b l e network p a t t e r n . A l o c a l i s e d r e g i o n o f t r a n s p a r e n t o r t r a n s l u c e n t e p i c a r p w i t h a w e l l - d e f i n e d f r o n t . Network p a t t e r n may have d i s a p p e a r e d as i n t e r n a l t i s s u e s s t a r t t o b r e a k down. A f f e c t e d a r e a -> 10 % but -<40% o f t h e t o t a l s u r f a c e a r e a o f t h e f r u i t . I n j u r y c o v e r s 40-60% o f the t o t a l s u r f a c e a r e a o f the f r u i t . A f f e c t e d a r e a i s c l o u d y except a t t h e a d v a n c i n g f r o n t . A f f e c t e d area>»60% o f the f r u i t s u r f a c e a r e a . T h i s s tage i s c h a r a c t e r i z e d by i n t e r n a l foaming due t o p o c k e t s o f gas i n the a f f e c t e d t i s s u e as i t b r e a k s down. F l u i d may s t a r t t o ooze out a t t h e s t y l a r e n d . The e n t r a p p e d p o c k e t s o f gas produce a m o s a i c whose i n t e n s i t y depends upon stage o f r i p e n e s s o f f r u i t b e f o r e t r e a t m e n t . A f f e c t e d a r e a c l o s e t o 100% o f t o t a l f r u i t s u r f a c e . The e p i c a r p on t h e s t y l a r h a l f ( p r o x i m a l t o r a d i a n t energy source) i s v e r y w r i n k l e d i n u n r i p e f r u i t s ; In r i p e f r u i t s , the e p i c a r p i s s p l i t . - 55 -i n a N o r t h - S o u t h d i r e c t i o n . T h e r e were f i v e f r u i t s p e r g l a s s t u b e . Some o f t h e g l a s s - t u b e s were s e a l e d on b o t h ends w i t h P l e x i g l a s p l a t e s . A p r e c i s i o n A n s c h u t z thermometer was p l a c e d w i t h f r u i t s t o i n d i c a t e t h e a i r t e m p e r a t u r e w i t h i n each t u b e . F r u i t s were exposed f o r 0, 2, 4, 6, 8 o r 10 h o u r s . They were c o l l e c t e d a t t h e end o f t h e t r e a t m e n t s and s t o r e d a t 2 0°C and 12 h o u r p h o t o p e r i o d f o r 7 d a y s . A f t e r s t o r a g e , t h e y were examined f o r any v i s i b l e s i g n s o f u n i l a t e r a l c o l o r d e f e c t . A f f e c t e d f r u i t s were r e c o r d e d as p e r c e n t a g e o f i n i t i a l number o f f r u i t s under each t r e a t m e n t . R a d i a t i o n Types U s i n g t h e t r e a t m e n t chambers d e s c r i b e d p r e v i o u s l y , t h i s e x p e r i m e n t was o r g a n i z e d as f o l l o w s : t h r e e 300 w a t t s PAR 56/2 MFL medium f l o o d , c o o l l u x i n c a n d e s c e n t lamps ( S y l v a n i a E l e c t r i c P r o d u c t s I n c . , D e n v e r , M a s s . ) s u p p l i e d t h e r a d i a t i o n f o r each o f t r e a t m e n t s 1 and 2. In t r e a t m e n t 1, t h e r a d i a n t energy was i n t e r c e p t e d by a 4 mm p l a i n g l a s s p l a t e (Cap) b e f o r e i t e n t e r e d t h e chamber. T r e a t m e n t 2 had a 6 cm deep w a t e r - b a t h as a f i l t e r , t h u s e n s u r i n g t h a t most o f t h e r a d i a t i o n r e c e i v e d a t t h e f r u i t s u r f a c e was i n t h e v i s i b l e p a r t o f t h e s p e c t r u m . Lamp h e i g h t s above t h e chambers f o r b o t h t r e a t m e n t s 1 and 2 were 75 and 30 c m , r e s p e c t i v e l y t o a c h i e v e e q u a l i r r a d i a n c e o f -2 690 W m a t t h e f r u i t s u r f a c e . - 56 -The h e a t e r d e s c r i b e d p r e v i o u s l y p r o v i d e d the " r a d i a t i o n " t h a t c o n s t i t u t e d t r e a t m e n t 3. In t r e a t m e n t 4, f r u i t s were e n c l o s e d i n 21 cm l o n g , 8 cm mouth g l a s s j a r s , s e a l e d and immersed t o t h e neck (18 cm) i n a c o n s t a n t t e m p e r a t u r e w a t e r - b a t h ( " M a g n i w h i r l " B l u e M E l e c t r i c C o . , I l l i n o i s , U . S . A . ) . A i r t e m p e r a t u r e s w i t h i n t h e j a r s were measured by a c o p p e r - c o n s t a n t a n t h e r m o c o u p l e s c o n n e c t e d t o a Comark E l e c t r o n i c thermometer. One o f t h e t r e a t m e n t chambers was k e p t a t 2 2°C i n t h e d a r k and s e r v e d as the c o n t r o l . A i r t e m p e r a t u r e was 40°C i n a l l t h e t r e a t m e n t s e x c e p t t h e c o n t r o l . A l l t r e a t m e n t s i n c l u d i n g t h e c o n t r o l were p r e -s e t t o t h e d e s i r e d t e m p e r a t u r e and t h e a c c u r a c y o f t h e r m o s t a t s e t t i n g was o b s e r v e d f o r a t l e a s t 2 h o u r s b e f o r e p l a c i n g f r u i t s i n them. A p a r t from t r e a t m e n t s 1 and 2, a b l a c k hood was u s e d o v e r t h e chambers t o keep t h e f r u i t s i n d a r k n e s s d u r i n g t r e a t m e n t . VTaveband E f f e c t s B o t h v i s i b l e and f u l l ( u n f i l t e r e d ) r a d i a t i o n were a c h i e v e d as d e s c r i b e d p r e v i o u s l y . A CBS 750 F a r - r e d f i l t e r was r e i n f o r c e d by i n s e r t i n g i t between two 3 mm t h i c k p l a i n g l a s s s h e e t s and t h i s f i l t e r arrangement was u s e d t o "cap" the chamber t o p r o d u c e n e a r i n f r a - r e d r a d i a t i o n . Long-wave r a d i a t i o n was s u p p l i e d from a h e a t i n g element as d e s c r i b e d - 57 -p r e v i o u s l y . In t h e f i r s t waveband e x p e r i m e n t , t h e i r r a d i a n c e was 500 W m 2 and a i r t e m p e r a t u r e was 50°C. In t h e second -2 waveband e x p e r i m e n t t h e i r r a d i a n c e was 600 W m a t t h e f r u i t s u r f a c e a t chamber a i r t e m p e r a t u r e o f 40°C. F o r t h e s o l a r r a d i a t i o n t r e a t m e n t , f r u i t s were p l a c e d i n 30 cm x 10 cm d i a m e t e r c y l i n d r i c a l g l a s s t u b e s as b e f o r e . The f l o o r o f each t u b e was packed w i t h D r i e r i t e and c o v e r e d w i t h a mesh t o p r e v e n t d i r e c t c o n t a c t between f r u i t and D r i e r i t e . The D r i e r i t e was used t o p r e v e n t m o i s t u r e c o n d e n s a t i o n as a r e s u l t o f the s e a l e d atmosphere a r o u n d f r u i t s . Both t e m p e r a t u r e and s p e c t r a l energy d i s t r i b u t i o n o f t h e i r r a d i a n c e under t h e v a r i o u s t r e a t m e n t s were r e c o r d e d ( F i g . 2 ) . E a c h s p e c t r a l t r a c e c o n s i s t e d o f -2 -1 s p e c t r a l i n t e n s i t y r e a d i n g s uW cm nm t a k e n a t 380 nm, 400 nm and a t 25 nm i n t e r v a l s between 400 and 750 i n t h e v i s i b l e range and a t 50 nm i n t e r v a l s between 750 and 1500 nm i n the i n f r a - r e d r a n g e . S w i t c h i n g o f t h e r a n g e s from v i s i b l e t o i n f r a - r e d r e s u l t e d i n two v a l u e s f o r 750 nm. H i g h T e m p e r a t u r e s Chamber a i r t e m p e r a t u r e s were m a i n t a i n e d a t 22°C ( C o n t r o l ) , 30°C, 50°C and 70°C i n t h e d a r k as d e s c r i b e d p r e v i o u s l y . F r u i t s were p l a c e d i n chambers s t y l a r end up f o r a 5 - h o u r t r e a t m e n t d u r a t i o n . - 58 -Figure 2. Spectral Energy D i s t r i b u t i o n of U n f i l t e r e d Radiation from 300 VJatts PAR 56/2MFL medium flood, cool lux incandescent Sylvania lamps (LUR) and the Sun SR: E f f e c t s of 2.5 cm deep water-bath and CBS 7 50 Far-red f i l t e r on the Spectral Energy D i s t r i b u t i o n of the Radiation from Sylvania lamps. -2 LUR 600 \-l m u n f i l t e r e d r a d i a t i o n from Sylvania lamps LWR ,: 2.5 cm deep water-bath f i l t e r e d r a d i a t i o n from Sylvania lamps LIR " Far-red f i l t e r e d r a d i a t i o n from Sylvania lamps SR " Spectral irradiance of the sun at noon i n the midsummer i n UBC. - 60 -Oxygen C o n c e n t r a t i o n A P l e x i g l a s a s s i m i l a t i o n chamber was used i n an e x p e r i m e n t t o d e t e r m i n e t h e e f f e c t o f d i f f e r e n t 0 2 l e v e l s on i n j u r y d e v e l o p m e n t . I r r a d i a n c e a t f r u i t l e v e l w i t h i n the - 2 chamber was 640 W m and t h e chamber a i r t e m p e r a t u r e was 37+3°C d u r i n g t h e c o u r s e o f t h e e x p e r i m e n t . Chamber a i r t e m p e r a t u r e was m a i n t a i n e d by a j a c k e t o f r u n n i n g c o l d w a t e r a l o n g the s i d e and b o t t o m o f t h e chamber. T h e r e was no w a t e r j a c k e t on t o p o f t h e chamber. One f r u i t was e n c l o s e d p e r chamber a t a t ime and e x c e p t d u r i n g C O 2 measurements, gas c o n t a i n i n g t h e d e s i r e d 0^ c o n c e n t r a t i o n was c o n t i n u o u s l y f l u s h e d t h r o u g h t h e chamber from a gas c y l i n d e r (Canadian L i q u i d A i r L t d . ) d u r i n g t h e t r e a t m e n t a t a r a t e o f 1 l i t e r p e r m i n u t e . A t 15 m i n u t e i n t e r v a l s , t h e chamber was s e a l e d o f f by c l o s i n g t h e t a p s a t t h e a i r i n l e t and a i r o u t l e t t u b i n g s and t h e chamber was then i m m e d i a t e l y c o n n e c t e d i n s e r i e s w i t h an a i r pump, a D r i e r i t e c y l i n d e r , a f lowmeter and an I n f r a - r e d gas a n a l y z e r (IRGA) i n a c l o s e d system ( F i g . 3 ) . The volume o f t h e c l o s e d s y s t e m was 1.10 l i t r e s and gas f low r a t e t h r o u g h the system was 1.6 l i t r e s min I r r a d i a t i o n was always v e r t i c a l l y downwards on f r u i t s p l a c e d s t y l a r end up w i t h i n t h e chamber. The e x p e r i m e n t was r u n two t i m e s f o r e a c h 0 2 c o n c e n t r a t i o n u s e d . - 61 -D R G A R F i g u r e 3. S c h e m a t i c Drawing o f t h e C l o s e d Gas Exchange System Used t o Measure C0» Exchange P a t t e r n s o f Tomato F r u i t s a t D i f f e r e n t 0„ C o n c e n t r a t i o n s , D u r i n g E x p o s u r e t o R a d i a n t E n e r g y . C F r u i t chamber; P A i r Pump; D D r i e r i t e C y l i n d e r ; F F l o w m e t e r ; IRGA I n f r a - r e d gas a n a l y z e r ; R S t r i p C h a r t R e c o r d e r . - 62 -C h a r a c t e r i z a t i o n o f F r u i t Responses t o I n j u r y  T r e a t m e n t S t a n d a r d i z a t i o n The t r e a t m e n t chambers were s e t a t a f i x e d i r r a d i a n c e o f 680 VI m 2 and an a i r t e m p e r a t u r e o f 40°C a t f r u i t l e v e l . Ten f r u i t s were i r r a d i a t e d f o r each o f 1, 2, 3, 4, 5, 6, 7 o r 8 h o u r s and t h e n s c o r e d f o r i n j u r y i m m e d i a t e l y a f t e r e a c h t r e a t m e n t d u r a t i o n . A s t a n d a r d c u r v e was t h u s d e v e l o p e d t o a c t as a g u i d e i n d e t e r m i n i n g t h e d u r a t i o n o f e x p o s u r e t h a t w o u l d p r o d u c e a s p e c i f i e d i n j u r y s c o r e i n s u b s e q u e n t e x p e r i m e n t s . Measurement o f P h y s i c a l C h a r a c t e r i s t i c s I n f r a - r e d A b s o r p t i o n S p e c t r a - Samples o f tomato f r u i t s were c u t i n t o p i e c e s i n 150 ml b e a k e r s and e n c l o s e d i n 1200 ml f a s t - f r e e z e f l a s k s and put i n a f r e e z e r f o r 5 h o u r s . The f l a s k s were t h e n t a k e n and c o n n e c t e d t o t h e m a n i f o l d s o f Labconco f r e e z e - d r y e r s and t h e f r u i t samples were d r i e d f o r 48 h o u r s . U s i n g an aluminum o x i d e m o r t a r (50 mm O . D . ) and p e s t l e , 0.2 g o f t h e ' f r e e z e - d r i e d samples were ground i n t o v e r y f i n e f r a g m e n t s , a d d i n g 2.5 ml o f s o l v e n t ( C h l o r o f o r m o r C a r b o n - t e t r a c h l o r i d e ) each t i m e . A f i l t e r i n g f u n n e l was made by p l u g g i n g a 10 cm l o n g 1 cm (O.D.) g l a s s tube drawn a t one - 63 -end w i t h f i b r e - g l a s s . A few d r o p s o f the s o l v e n t were added t o wet t h e f i b r e - g l a s s . T h e n , u s i n g a P a s t e u r p i p e t t e , a sample was withdrawn from t h e m o r t a r i n t o t h e f i l t e r i n g f u n n e l . The f i r s t few d r o p s o f t h e f i l t r a t e were d i s c a r d e d w h i l e t h e r e m a i n d e r was c o l l e c t e d i n a 10 ml t e s t t u b e . A b s o r p t i o n s p e c t r a o f t h e c l e a r s o l u t i o n s were d e t e r m i n e d between 700 and 2500 nm on a C a r y (Model 17D) S p e c t r o p h o t o m e t e r u s i n g IR v i t r e o s i l c e l l s (10 mm p a t h l e n g t h ) . A b s o r p t i o n i n t h e waveband 2.5 t o 14 u was d e t e r m i n e d w i t h a Unicam ( S . P . 200G G r a t i n g I n f r a r e d ) S p e c t r o p h o t o m e t e r by u s i n g a c e l l mount i n the f o l l o w i n g way. S o l u t i o n was withdrawn i n a h y p o d e r m i c s y r i n g e and i n j e c t e d i n t o the L u e r p o r t s o f a W i l k s p r e c i s i o n s e a l e d l i q u i d c e l l w h i c h was t h e n c a p p e d . The c e l l was mounted o n t o t h e Unicam S p e c t r o p h o t o m e t e r and t h e a b s o r p t i o n spectrum was s c a n n e d . F o r c e - D e f o r m a t i o n C h a r a c t e r i s t i c s - A 3 cm l o n g p r o b e w i t h a 1 mm d i a m e t e r t i p was c o n s t r u c t e d and screwed on t o a c h u c k . The chuck was a t t a c h e d t o t h e I n s t r o n U n i v e r s a l T e s t i n g M a c h i n e t o p e r f o r m p u n c t u r e t e s t s ( F i g . 4 ) . The t i p o f the p r o b e was f l a t . A 1 mm d i a m e t e r p r o b e was u s e d b e c a u s e i t was found i n p r e l i m i n a r y t e s t s t o p r o d u c e the l e a s t a r e a o f l o c a l d e f o r m a t i o n on t h e f r u i t s . - 64 -Figure 4. Inst r o n T e s t i n g Machine Showing the Puncture Probe Attachment Used i n the Measurement of Force-Deformation C h a r a c t e r i s t i c s . - 65 -T h r e e p o s i t i o n s : " s t y l a r " , " e q u a t o r i a l " , and " c a l y x " , were i d e n t i f i e d on t h e f r u i t ( F i g . 5 ) . Each f r u i t was a l i g n e d u n d e r the probe on a f l a t aluminum p l a t e and was s u p p o r t e d by moulded s t u d s o f m o d e l l i n g c l a y . The c a l y x a x i s was a t r i g h t a n g l e t o t h e d i r e c t i o n o f f o r c e a p p l i c a t i o n f o r b o t h t h e e q u a t o r i a l and c a l y x p o s i t i o n d e t e r m i n a t i o n s . F o r t h e s t y l a r end d e t e r m i n a t i o n , f r u i t s were a l i g n e d s t y l a r end up i n the d i r e c t i o n o f t h e p r o b e . The f o r c e t r a n s d u c e r and s t r i p c h a r t r e c o r d e r were a d j u s t e d t o p r o v i d e a f u l l s c a l e s e n s i t i v i t y o f 1 k g . T h r e e f r u i t s were measured p e r t r e a t m e n t . Two d e t e r m i n a t i o n s were made p e r p o s i t i o n a t p o i n t s away from t h e l o c u l a r r i d g e , a t a c r o s s h e a d speed o f 20 mm/minute and a c h a r t speed o f 100 mm/ m i n u t e . A t y p i c a l f o r c e - d e f o r m a t i o n c u r v e i s shown i n F i g u r e 6. S i x p h y s i c a l c h a r a c t e r i s t i c s were d e t e r m i n e d from t h e s t r i p c h a r t f o r c e - d e f o r m a t i o n c u r v e s . A d e s c r i p t i o n o f e a c h p h y s i c a l c h a r a c t e r i s t i c and t h e u n i t s o f measurement a r e shown i n T a b l e 3. An i n i t i a l t r i a l c l e a r l y showed t h a t t h r e e o f t h e p h y s i c a l c h a r a c t e r i s t i c s , P e r i c a r p s t r e n g t h , D e f o r m a t i o n and Toughness were i n f l u e n c e d by f r u i t s i z e (Table 4 ) . A l l t h r e e d e c r e a s e d as f r u i t s i z e i n c r e a s e d . The o t h e r t h r e e c h a r a c t e r i s t i c s , Mesocarp r e s i s t a n c e , C o m p l i a n c e and F i r m n e s s showed comparable r e s u l t s i r r e s p e c t i v e o f s i z e . F r u i t s used f o r s u b s e q u e n t measurement o f p h y s i c a l c h a r a c t e r i s t i c s were p r e - s e l e c t e d f o r shape and w e i g h t b e f o r e t r e a t m e n t so t h a t t h e d i f f e r e n c e , - 66; -F i g u r e 5. F r u i t P o s i t i o n D e m a r c a t i o n f o r P u n c t u r e T e s t s : 1. ' ' S t y l a r " R e g i o n ; 2. " E q u a t o r i a l " R e g i o n ; 3. " C a l y x " R e g i o n . - 67 -D i s tance mm F i g u r e 6 . T y p i c a l F o r c e - D e f o r m a t i o n Curve O b t a i n e d D u r i n g P u n c t u r e T e s t s Showing How F o r c e - D e f o r m a t i o n C h a r a c t e r i s t i c s were D e t e r m i n e d : a D e f o r m a t i o n (mm) b P e r i c a r p S t r e n g t h (g) c Mesocarp R e s i s t a n c e (g) _^ a/b C o m p l i a n c e (mm g_^) b / a F i r m n e s s (g mm ) b ci —'TT— Toughness (g mm) T a b l e 3. D i m e n s i o n a l A n a l y s i s o f the F o r c e - D e f o r m a t i o n Curve o f Tomato F r u i t s O b t a i n e d from t h e I n s t r o n T e s t i n g M a c h i n e . C h a r a c t e r i s t i c P a r a m e t e r D e s c r i p t i o n Measured V a r i a b l e D i m e n s i o n s D e f o r m a t i o n Amount o f c o m p r e s s i o n t h a t o c c u r s on f r u i t t i s s u e b e f o r e b r e a k i n g t h r o u g h t h e e p i c a r p P e r i c a r p S t r e n g t h M a g n i t u d e o f f o r c e r e q u i r e d t o b r e a k t h r o u g h the p e r i c a r p o f t h e f r u i t d i s t a n c e mm Mesocarp R e s i s t a n c e C o m p l i a n c e F i r m n e s s Toughness R e s i d u a l f o r c e a f t e r b r e a k i n g t h r o u g h the e x o c a r p Rate o f change i n d e f o r m a t i o n p e r u n i t f o r c e F o r c e r e q u i r e d t o produce u n i t d e f o r m a t i o n o f f r u i t t i s s u e The t o t a l e n e r g y a b s o r b e d by f r u i t b e f o r e b r e a k i n g t h r o u g h t h e p e r i c a r p f o r c e f o r c e R a t i o o f d i s t a n c e o v e r f o r c e f o r c e p e r u n i t d i s t a n c e p r o d u c t o f f o r c e and d i s t a n c e mm g -1 g mm g mm -1 CO T a b l e 4. E f f e c t s o f F r u i t S i z e on t h e D e t e r m i n a t i o n o f F o r c e - D e f o r m a t i o n C h a r a c t e r i s t i c s o f Tomato F r u i t s by the I n s t r o n U n i v e r s a l T e s t i n g M a c h i n e , U s i n g a M o d i f i e d P u n c t u r e Probe 1 mm Diameter T i p . FRUIT SIZE FORCE-DEFORMATION CHARACTERISTICS . i _ 4 _ * p» \c ltriCall mesocarp C o m p l i a n c e F i r m n e s s Toughness W e i g h t * D e f o r m a t i o n S t r e n g t h R e s i s t a n c e f_1 _ 2 _ 1 D e s c r i p t i o n g mm g g mm g xlO g mm g mm S m a l l 85.10 22.5 291.0 12.5 7.73 12.96 3228 L a r g e 138.95 11.8 158.0 13 .3 7.49 13. 40 968 A v e r a g e w e i g h t o f two f r u i t s . T h r e e d e t e r m i n a t i o n s were made p e r f r u i t a t the " s t y l a r " r e g i o n . F r u i t s u s e d i n P u n c t u r e T e s t s were a t t h e s t a g e 6 ( F u l l r e d b u t s o f t ) r i p e n e s s . - 70 -i n w e i g h t between t h e s m a l l e s t and t h e b i g g e s t was n o t more t h a n 10 g- Mean f r u i t w e i g h t i n the p h y s i c a l s t u d i e s was 100.25 g . Measurement o f Some C h e m i c a l C h a r a c t e r i s t i c s P r o t o p e c t i n - T w e n t y - f i v e g samples o f f r u i t t i s s u e were o b t a i n e d , s a m p l i n g from t h e s t y l a r e n d , and e a c h sample was p l a c e d i n a b l e n d e r cup and b l e n d e d w i t h 250 ml o f 95% e t h a n o l f o r 2-3 m i n u t e s u s i n g an O s t e r i z e r b l e n d e r . The b l e n d e d m a t e r i a l was a l l o w e d t o s t a n d f o r 1 h o u r , a f t e r w h i c h t h e s u p e r n a t a n t was removed by f i l t e r a t i o n t h r o u g h a Whatman No. 1 f i l t e r p a p e r under s u c t i o n . The a l c o h o l - i n s o l u b l e r e s i d u e was washed once w i t h 95% e t h a n o l and t w i c e w i t h 70% e t h a n o l . The m o i s t r e s i d u e and f i l t e r p a p e r were t r a n s f e r r e d i n t o a 500 ml b e a k e r and 300 ml d i s t i l l e d w a t e r were a d d e d . About 5 d r o p s o f T o l u e n e were added and t h e m i x t u r e was s t i r r e d w i t h a m a g n e t i c s t i r r e r . The r e m a i n d e r o f the a n a l y s i s f o l l o w e d t h e p r o c e d u r e o f Kanujoso and Luh (1967). P e c t i n c o n t e n t was d e t e r m i n e d c o l o r i m e t r i c a l l y a c c o r d i n g t o t h e method o f McComb and McCready (19 5 2 ) . A s t a n d a r d c u r v e was c o n s t r u c t e d u s i n g D - g a l a c t u r o n i c a c i d (Sigma) o v e r a c o n c e n t r a t i o n range o f 0 to 50 p g / m l . The r e s u l t s were e x p r e s s e d as mg% AUA ( A n h y d r o u r o n i c a c i d ; 4 0 ug G a l a c t u r o n i c a c i d h y d r a t e = 33.2 jug A U A ) . - 71 -A s c o r b i c A c i d - A s c o r b i c a c i d c o n t e n t was d e t e r m i n e d as r e d u c e d a s c o r b i c a c i d a c c o r d i n g t o t h e method o f Ruck (1963) w h i c h was a d a p t e d f o r use on the Bausch and Lomb S p e c t r o n i c 20 s p e c t r o p h o t o m e t e r u s i n g 2, 6 - d i c h l o r o b e n z e n o n e i n d o p h e n o l ( F i s h e r ) s t a n d a r d i z e d w i t h L - a s c o r b i c a c i d (Matheson Coleman and B e l l ) . T w e n t y - f i v e g samples were t a k e n i n t r i p l i c a t e , one sample p e r f r u i t , s a m p l i n g each t i m e from t h e s t y l a r e n d . D u p l i c a t e measurements were made p e r sample and v a l u e s were r e c o r d e d as t h e a v e r a g e o f two measurements. pH - T h r e e 100 g samples were o b t a i n e d , each from a p o o l e d sample o f two f r u i t s , b l e n d e d f o r 3 m i n u t e s a t slow speed i n an O s t e r i z e r b l e n d e r and f i l t e r e d u s i n g two l a y e r s o f cheese c l o t h . The pH o f t h e f i l t e r e d s o l u t i o n was d e t e r m i n e d u s i n g a Beckman Z e r o m a t i c pH Meter p r e v i o u s l y s t a n d a r d i z e d w i t h a pK 4.0 s t a n d a r d b u f f e r s o l u t i o n (American S c i e n t i f i c and C h e m i c a l ) . Lycopene - T h r e e 20 g samples were t a k e n from t h e s t y l a r end o f d i f f e r e n t tomato f r u i t s . E a c h sample was b l e n d e d w i t h 75 ml a c e t o n e i n i t i a l l y a t a slow speed t h e n a t a f a s t speed i n an O s t e r i z e r b l e n d e r and c a r o t e n e s were e x t r a c t e d a c c o r d i n g t o t h e method o f Z s c h e i l e and P o r t e r - 72 -(1947). Measurements were t a k e n as a b s o r b a n c e a t 501 nm u s i n g a Double beam Unicam P200 S p e c t r o p h o t o m e t e r . Lycopene c o n t e n t was d e t e r m i n e d from a s t a n d a r d c u r v e w h i c h was d e v e l o p e d u s i n g s t a n d a r d Lycopene (Sigma). Measurement o f F r u i t Gas Exchange and Water L o s s -2 F r u i t s were i r r a d i a t e d w i t h 680 W m u n f i l t e r e d r a d i a t i o n from S y l v a n i a i n c a n d e s c e n t lamps a t 4 0°C a i r t e m p e r a t u r e f o r 0, 1, 2 o r 5 h o u r s t o p r o d u c e i n j u r y s c o r e s o f 0 ( " u n t r e a t e d " ) , - C I ( " i n d u c t i o n " ) , 1 ( " i n c i p i e n t " ) and 3 ("advanced") r e s p e c t i v e l y . S i m i l a r l y t r e a t e d f r u i t s , were t h e n grouped i n t o p a i r s . T h e r e were t h r e e p a i r s p e r t r e a t m e n t . Gas exchange measurement commenced a t 10 o ' c l o c k a.m. each day w i t h t h e d e t e r m i n a t i o n o f C O 2 exchange , f o l l o w e d by a s s a y o f e t h y l e n e e v o l u t i o n and t h e water l o s s on each s e t . F o r e a c h p a i r , t h e r e was a p e r i o d o f two h o u r s between CG^ and e t h y l e n e measurements, and a f u r t h e r two h o u r s between the e t h y l e n e e v o l u t i o n and m o i s t u r e l o s s d e t e r m i n a t i o n s . Carbon D i o x i d e - A s i m p l e c l o s e d system was used f o r t h e measurement o f f r u i t r e s p i r a t i o n . The f r u i t chambers were S y b r o n / N a l g e wide-mouth 2 l i t r e b o t t l e s . Two r u b b e r s e p t a 4 cm a p a r t were f i x e d i n t o t h e b o t t l e c o v e r s , and h o l e s - 73 -were d r i l l e d i n t o e a c h septum i n t o w h i c h g l a s s t u b i n g s were f i x e d . The t u b i n g s a c t e d as i n l e t and o u t l e t s u p p o r t s f o r t h e Tygon t u b i n g . The c o v e r s were a l s o f i x e d on the i n s i d e w i t h r u b b e r g a s k e t r i n g s and gas l e a k s were f u r t h e r p r e v e n t e d by a p p l y i n g s i l i c o n e g r e a s e t o a l l j o i n t s . The f r u i t chamber was l i n k e d i n s e r i e s w i t h a Beckman model 864 I n f r a r e d gas a n a l y z e r (IRGA), a "Neptune Dyna-pump" (VMR S c i e n t i f i c ) a i r pump, and a Matheson 603 f lowmeter u s i n g Tygon t u b i n g . A F i s h e r R e c o r d a l l 5000 s t r i p c h a r t r e c o r d e r was c o n n e c t e d t o t h e IRGA and i t r e c o r d e d the CC^ c o n c e n t r a t i o n s measured by t h e IRGA. The volume o f t h e c l o s e d system was 2.10 l i t r e s and a i r was c i r c u l a t e d t h r o u g h t h e system a t 2 l i t r e s min ^. CC^ exchange measurements l a s t e d 10 m i n u t e s p e r f r u i t p a i r p e r d a y . E t h y l e n e - F r u i t s were i n c u b a t e d i n 1 l i t r e S y b r o n / N a l g e b o t t l e s f o r 3 0 m i n u t e s each d a y . D u p l i c a t e 1 ml samples were withdrawn and e t h y l e n e c o n c e n t r a t i o n i n t h o s e samples was d e t e r m i n e d on a H e w l e t t P a c k a r d Gas Chromatograph model 5830A w i t h a H e w l e t t P a c k a r d G . C . T e r m i n a l model 18850A. The gas c h r o m a t o g r a p h had a Poropak N column and a Flame I o n i z a t i o n D e t e c t o r . On t h e gas c h r o m a t o g r a p h , the i n j e c t i o n p o r t , oven and d e t e c t o r t e m p e r a t u r e s , w e r e 105, 80 and 130°C r e s p e c t i v e l y . The e t h y l e n e r e t e n t i o n t i m e a t a c a r r i e r gas f low r a t e o f 19 c c / m i n was 1.15 m i n u t e s . The c a r r i e r gas - 74 was n i t r o g e n . E t h y l e n e c o n c e n t r a t i o n s i n samples were a u t o m a t i c a l l y c a l c u l a t e d i n ppm by t h e gas c h r o m a t o g r a p h T e r m i n a l based on known s t a n d a r d s p r o v i d e d t o t h e T e r m i n a l e a c h day b e f o r e measurement. M o i s t u r e L o s s - F r u i t s were weighed each day a f t e r t h e CC»2 exchange and e t h y l e n e measurement were done. The change i n f r u i t w e i g h t was c a l c u l a t e d and e x p r e s s e d as p e r c e n t a g e o f t h e i n i t i a l f r u i t f r e s h w e i g h t a t the s t a r t o f e x p e r i m e n t . C o n t r o l o f I n j u r y -2 U s i n g s t a n d a r d t r e a t m e n t c o n d i t i o n s (680 W m i r r a d i a n c e a t 40°C a i r t e m p e r a t u r e ) f r u i t s were i r r a d i a t e d f o r 1 h o u r o r 4 h o u r s , p r o d u c i n g c o r r e s p o n d i n g i n j u r y l e v e l s o f *C 1 ( u n d e t e c t a b l e a f t e r t r e a t m e n t ) o r ^ 2 . 0 . Ten f r u i t s i n each c a t e g o r y were k e p t i n each o f v a r i o u s s t o r a g e c o n d i t i o n s o f c o n t i n u o u s d a r k n e s s , 12 hour p h o t o p e r i o d and c o n t i n u o u s l i g h t a t 10°C o r 22°C. In a n o t h e r t r i a l , u n i n j u r e d p o r t i o n s o f i r r a d i a t e d f r u i t s were k e p t i n d a r k n e s s by u s i n g b l a c k p o l y e t h y l e n e wrappers w h i l e t h e i n j u r e d p o r t i o n s were exposed t o v a r y i n g p h o t o p e r i o d o r Qt^ l e v e l s a t 25°C f o r s e v e r a l d a y s . A t t h e end o f t h e s t o r a g e p e r i o d , f r u i t s were examined f o r changes i n i n j u r y l e v e l s . - 75 -Data A n a l y s i s F o r c e - D e f o r m a t i o n C h a r a c t e r i s t i c s , P r o t o p e c t i n ,  A s c o r b i c A c i d and pH In e a c h o f t h e above s t u d i e s , the e f f e c t s o f f o u r s t a g e s o f r i p e n e s s , t h r e e l e v e l s o f i n j u r y and s t o r a g e were i n v e s t i g a t e d . U s i n g t h r e e chambers, t w e n t y - f o u r f r u i t s made up o f s i x f r u i t s p e r r i p e n e s s s t a g e o f 0 ( " M a t u r e - g r e e n " ) , 1 ( " T u r n i n g " ) , 3 ( " P i n k " ) , and 5 ( " F i r m r e d " ) , were p l a c e d a t random i n t h e chambers and i r r a d i a t e d a t a f i x e d i r r a d i a n c e o f 680 W m 2 and 4 0°C a i r t e m p e r a t u r e . E i g h t f r u i t s made up o f two f r u i t s p e r r i p e n e s s c a t e g o r y were w i t h d r a w n a t 0, 2 o r 5 h o u r s a f t e r t h e s t a r t o f t r e a t m e n t , p r o d u c i n g c o r r e s p o n d i n g i n j u r y l e v e l s 0 ("untreated") , 1 ( " I n c i p i e n t " ) and 3 ("advanced") r e s p e c t i v e l y . One f r u i t p e r r i p e n e s s c a t e g o r y was a n a l y z e d w i t h i n 24 h o u r s w h i l e t h e o t h e r was s t o r e d u n t i l u n i f o r m p h y s i o l o g i c a l s t a g e (Ripeness s t a g e 6) was r e a c h e d b e f o r e i t was u s e d f o r t h e measurement o f f o r c e - d e f o r m a t i o n c h a r a c t e r i s t i c s o r a n a l y s i s o f p r o t o p e c t i n , a s c o r b i c a c i d o r p H . An i n d i v i d u a l f r u i t was u s e d f o r o n l y one a n a l y s i s . The e x p e r i m e n t was r u n t h r e e t i m e s f o r each a n a l y s i s . Each e x p e r i m e n t was t r e a t e d as a 3 (Run) x 4 (Ripeness) x 3 ( I n j u r y ) x 2 (Storage) f a c t o r i a l and s t a t i s t i c a l a n a l y s i s was p e r f o r m e d u s i n g the UBC MFAV c o m p u t e r . C o r r e l a t i o n s t u d i e s and r e g r e s s i o n a n a l y s i s were done u s i n g t h e UBC TRP computer p r o g r a m . - 7 6 -RESULTS R e p o r t s o f t h e o c c u r r e n c e o f s u n s c a l d and s i m i l a r s u n - m e d i a t e d i n j u r i e s of tomatoes have come m o s t l y from hot and humid t r o p i c a l and s u b - t r o p i c a l r e g i o n s o f the w o r l d . However, i t i s known t h a t summer c o n d i t i o n s i n t e m p e r a t e r e g i o n s a r e c o m p a r a b l e t o t h o s e o f t h e t r o p i c s . A s e r i e s o f t r i a l s were t h e r e f o r e c a r r i e d o u t t o e s t a b l i s h whether t h e s u n s c a l d syndrome c o u l d be p r o d u c e d i n t e m p e r a t e B r i t i s h C o l u m b i a d u r i n g the summer. E f f e c t o f E n v i r o n m e n t and T r e a t m e n t D u r a t i o n on I n j u r y Development T a b l e 5 shows t h a t s u n s c a l d i n j u r y c o u l d be i n d u c e d b o t h o u t d o o r s and i n t h e g r e e n h o u s e . A much g r e a t e r p e r c e n t a g e o f f r u i t s w i t h n o t i c e a b l e i n j u r y was found when f r u i t s were e n c a s e d i n 30 cm X 10 cm (O.D.) c y l i n d r i c a l o p e n - e n d e d g l a s s t u b e s . S e a l i n g o f t h e g l a s s t u b e s f u r t h e r i n c r e a s e d the d e g r e e o f i n j u r y . The l o w e s t p e r c e n t a g e o f i n j u r e d f r u i t s o c c u r r e d among tomatoes t r e a t e d under g r e e n h o u s e c o n d i t i o n s . E x p o s u r e p e r i o d s o f l e s s t h a n 4 , h o u r s p r o d u c e d d e t e c t a b l e i n j u r y i n a t l e a s t 50% o f t h e f r u i t s when t h e y were e n c l o s e d i n g l a s s - t u b e s . E x p o s u r e s o f 10 hour d u r a t i o n p r o d u c e d d e t e c t a b l e i n j u r y i n o n l y about 30% o f t h e f r u i t s i n t h e g r e e n h o u s e . I r r e s p e c t i v e o f e n v i r o n m e n t , t h e p e r c e n t a g e o f i n j u r e d f r u i t s i n c r e a s e d w i t h d u r a t i o n o f e x p o s u r e . T a b l e 5. E f f e c t s o f E n v i r o n m e n t and Treatment D u r a t i o n on i n j u r y Development. % F r u i t s W i t h N o t i c e a b l e I n j u r y * E n v i r o n m e n t D u r a t i o n (hr) 0 2 4 6 8 10 Greenhouse 0 . 0 0 20 20 3 0 Open a i r 0 0 30 40 60 90 G l a s s tube (open end) 0 20 70 90 100 100 G l a s s t u b e ( s e a l e d ) 0 80 100 100 100 100 * F r u i t s were a s s e s s e d a f t e r 7 days i n s t o r a g e . 10 f r u i t s / t r e a t m e n t I n j u r y was s c o r e d as any s i g n o f sunken s u r f a c e a r e a w i t h d e f e c t i v e c o l o r a t i o n a t t h e s t y l a r h a l f o f f r u i t s w h i l e t h e r e m a i n i n g f r u i t s u r f a c e a t t a i n e d f u l l r e d c o l o u r . - 78 -These r e s u l t s d e m o n s t r a t e d t h a t i n j u r y can d e v e l o p on d e t a c h e d tomato f r u i t s exposed t o s o l a r r a d i a t i o n d u r i n g t h e summer i n B r i t i s h C o l u m b i a . They c o n f i r m t h e work o f R e t i g and Kedar (1967) who showed t h a t e x p o s u r e o f d e t a c h e d tomato f r u i t s t o d i r e c t s o l a r r a d i a t i o n p r o d u c e d s u n s c a l d . The t r i a l r a i s e d s e v e r a l q u e s t i o n s most o f w h i c h c o u l d n o t be answered due t o t h e l a r g e l y u n c o n t r o l l e d n a t u r e o f t h e e x p e r i m e n t . L i p t o n (1970a and b) had shown t h a t h i g h t e m p e r a t u r e s and h i g h r e l a t i v e h u m i d i t y c a u s e d n e c r o s i s o f p a r t i a l l y expanded l e a f l e t s as w e l l as p o o r f r u i t c o l o r a t i o n o f tomatoes grown i n t h e g r e e n h o u s e . The enhancement o f i n j u r y i n t h e open a i r o v e r t h e greenhouse c o u l d n o t be e x p l a i n e d on t h e b a s i s o f L i p t o n 1 s r a t i o n a l e s i n c e b o t h t e m p e r a t u r e and h u m i d i t y i n the open a i r were l o w e r t h a n i n t h e g r e e n h o u s e . R a t h e r , i t was t h o u g h t t h a t t h e g r e a t e r o c c u r r e n c e o f i n j u r y i n t h e open a i r might p o s s i b l y be due t o t h e f i l t e r i n g out o f c e r t a i n wavebands by the f i b r e g l a s s s h e e t s u s e d f o r t h e greenhouse c o v e r i n g o r s i m p l y a r e d u c t i o n i n t h e r a d i a n t f l u x d e n s i t y . F r u i t t e m p e r a t u r e s have been known t o r i s e s i g n i f i c a n t l y above a i r t e m p e r a t u r e s e s p e c i a l l y a t low wind speeds ( H a l l 1964, T h o r p e 1974). The g r e a t e r i n c i d e n c e o f i n j u r y i n f r u i t s e n c l o s e d i n t h e g l a s s t u b e s was p r o b a b l y due t o a r e d u c t i o n o f wind v e l o c i t y by the g l a s s s h i e l d and t h e r e f o r e r e d u c e d c o n v e c t i v e h e a t l o s s . In t h e c a s e o f the s e a l e d g l a s s - t u b e s t h e enhanced i n j u r y was p r o b a b l y due t o a c o m b i n a t i o n o f t e m p e r a t u r e and - 79' -h i g h r e l a t i v e h u m i d i t y as s u g g e s t e d by L i p t o n (1970b). The a i r t e m p e r a t u r e i n t h e s e a l e d g l a s s - t u b e was 4 0°C a t the end o f t h e e x p e r i m e n t . I n i t i a l E v a l u a t i o n o f t h e E f f e c t s o f D i f f e r e n t R a d i a t i o n  and T e m p e r a t u r e T r e a t m e n t s on I n j u r y Development As a r e s u l t o f t h e i s s u e s r a i s e d above, an e x p e r i m e n t was c a r r i e d o u t under c o n t r o l l e d c o n d i t i o n s t o e v a l u a t e t h e e f f e c t i v e n e s s o f d i f f e r e n t t y p e s o f r a d i a t i o n i n c a u s i n g t h e i n j u r y . A l l t r e a t m e n t s were a p p l i e d a t a i r t e m p e r a t u r e s o f 4 0°C s i n c e t h a t t e m p e r a t u r e was a s s o c i a t e d w i t h t h e g r e a t e s t o c c u r r e n c e o f i n j u r y d u r i n g t h e p r e l i m i n a r y t r i a l . S i m i l a r l y , an i r r a d i a n c e o f s i m i l a r magnitude t o t h a t o f t h e open a i r was a l s o employed. The r e s u l t s o f t h e e x p e r i m e n t a r e p r e s e n t e d i n F i g u r e 7. A t a chamber a i r t e m p e r a t u r e o f 40°C, a 5 hour t r e a t m e n t -2 . w i t h 690 W m u n f i l t e r e d r a d i a t i o n from an i n c a n d e s c e n t 300 W lamp s o u r c e was t h e most e f f e c t i v e i n c a u s i n g i n j u r y . The w a t e r b a t h - f i l t e r e d r a d i a t i o n o f comparable i r r a d i a n c e from t h e same s o u r c e p r o d u c e d o n l y a s l i g h t i n j u r y . R a d i a t i o n from t h e h e a t i n g e l e m e n t and " t e m p e r a t u r e " a p p l i e d t h r o u g h a hot w a t e r b a t h c o u l d n o t p r o d u c e a m e a s u r a b l e i n j u r y a t the same a i r t e m p e r a t u r e and o v e r t h e same p e r i o d . - 8.0 -F i g u r e 7. E f f e c t i v e n e s s o f D i f f e r e n t S o u r c e s o f R a d i a t i o n i n C a u s i n g I n j u r y on Detached Tomato F r u i t s a t 40 C A i r T e m p e r a t u r e : -2 LUR 690 W m u n f i l t e r e d r a d i a t i o n from 300 Watts PAR 5 6/2 MFL medium f l o o d , c o o l l u x i n c a n d e s c e n t S y l v a n i c ^ l a m p s . LWR 69 0 W m w a t e r - b a t h f i l t e r e d r a d i a t i o n from 300 Watts PAR 56/2 MFL medium f l o o d , c o o l l u x i n c a n d e s c e n t S y l v a n i a l a m p s . HER R a d i a t i o n from a h e a t i n g e l e m e n t . HWR " R a d i a t i o n " from a c o n s t a n t t e m p e r a t u r e h o t w a t e r - b a t h . CON U n t r e a t e d c o n t r o l a t 22°C. T r e a t m e n t l a s t e d 5 h o u r s . * E a c h v a l u e i s an average o f 12 f r u i t s ; I n j u r y was s c o r e d on a s c a l e o f 0-5 i m m e d i a t e l y a f t e r t r e a t m e n t . - 81 -A l l t r e a t m e n t s r e s u l t e d i n h i g h e r m o i s t u r e l o s s t h a n t h e c o n t r o l . The g r e a t e s t m o i s t u r e l o s s , measured as % change i n f r u i t f r e s h w e i g h t , was a s s o c i a t e d w i t h the t r e a t m e n t t h a t p r o d u c e d t h e h i g h e s t s c o r e o f i n j u r y . The t r e n d i n w e i g h t l o s s t e n d e d t o f o l l o w t h e p a t t e r n o f i n j u r y , b u t a s e v e r e w e i g h t l o s s d i d n o t a p p e a r t o be a p r e r e q u i s i t e f o r the i n i t i a t i o n o f i n j u r y . F o r example, t h e h o t water b a t h t r e a t m e n t r e s u l t e d i n a g r e a t e r w e i g h t l o s s t h a n water b a t h -f i l t e r e d r a d i a t i o n from a lamp s o u r c e but d i d n o t i n d u c e any m e a s u r a b l e i n j u r y . I t must be p o i n t e d o u t , however, t h a t a b s o l u t e c o m p a r i s o n s between t h e s e t r e a t m e n t s , and e s p e c i a l l y between t h e hot water b a t h and t h e o t h e r t r e a t m e n t s , a r e d i f f i c u l t t o make s i n c e t h e methods o f a p p l y i n g t h e t r e a t m e n t s were d i f f e r e n t . Compared w i t h t h e h o t w a t e r - b a t h , a l l o t h e r t r e a t m e n t s were a p p l i e d u n i d i r e c t i o n a l l y and had g r e a t e r volume o f a i r space p e r q u a n t i t y o f t r e a t m e n t m a t e r i a l . A l t h o u g h t r e a t m e n t chamber a i r t e m p e r a t u r e s were t h e same i n a l l t h e t r e a t m e n t s , e x c e p t f o r t h e c o n t r o l , f r u i t t e m p e r a t u r e s v a r i e d a c c o r d i n g t o t h e d u r a t i o n and n a t u r e o f t h e t r e a t m e n t ( F i g . 8 ) . G e n e r a l l y , f r u i t t e m p e r a t u r e r o s e s t e e p l y a t t h e s t a r t o f t r e a t m e n t and c o n t i n u e d t o r i s e u n t i l a maximum was r e a c h e d and t h e r e a f t e r r e m a i n e d more o r l e s s c o n s t a n t . T r e a t m e n t s t h a t p r o d u c e d the most s e v e r e i n j u r y a l s o r e s u l t e d i n t h e h i g h e s t f r u i t t e m p e r a t u r e s and the most r a p i d i n c r e a s e i n f r u i t t e m p e r a t u r e s . T e m p e r a t u r e s d e c r e a s e d w i t h d e p t h w i t h i n t h e f r u i t ( F i g . 8 b ) , and a t any s p e c i f i c d e p t h i n c r e a s e d w i t h d u r a t i o n o f t r e a t m e n t . The p a t t e r n o f - 82 -F i g u r e 8 (a). F r u i t Surface Temperatures* During Exposure of Detached Tomato F r u i t s t o : LUR 690 W m~2 u n f i l t e r e d r a d i a t i o n from 300 Watts PAR 56/ 2 MFL medium f l o o d , c o o l lux incandescent _ 2 S y l v a n i a lamps LWR 690 W m water-bath f i l t e r e d r a d i a t i o n from 300 Watts PAR 56/2MFL medium f l o o d , c o o l lux incandescent lamps HER R a d i a t i o n from a Heating Element HWR "Radiation'' from a constant temperature Hot Water-bath C o n t r o l u n t r e a t e d f r u i t s kept a t 22°C * A i r temperature i n a l l treatments was maintained a t 4 0°C throughout the d u r a t i o n of treatment. (b) F r u i t Temperatures at Various Depths During Exposure to U n f i l t e r e d R a d i a t i o n From 300 Watts PAR 56/2MFL Medium Flood, Cool Lux S y l v a n i a Lamps (LUR) - 33 -TIME , min T a b l e 6. R e l a t i v e E f f e c t i v e n e s s o f D i f f e r e n t R a d i a t i o n T r e a t m e n t s i n C a u s i n g T e m p e r a t u r e Changes i n Tomato F r u i t s D u r i n g T r e a t m e n t . T r e a t m e n t R e l a t i v e E f f e c t i v e n e s s * 690 Wm 2 LUR 40°C 5 h r 10 690 W m 2 LWR 40°C 5 h r 3.58 HER 40°C 5 h r HWR 40 C 5 h r CONTROL 20 C 5 h r 3.12 1.90 No Change R e l a t i v e e f f e c t i v e n e s s was c a l c u l a t e d as 100 "eq where t m = t i m e i n m i n u t e s t a k e n f o r f r u i t t e m p e r a t u r e t o e q u a l a i r t e m p e r a t u r e "T eq LUR LWR = HER = HWR = U n f i l t e r e d r a d i a t i o n from 300 Watts PAR 56/2 MFL medium f l o o d , c o o l l u x i n c a n d e s c e n t lamps W a t e r b a t h f i l t e r e d r a d i a t i o n from 300 Watts PAR 56/2 MFL medium f l o o d , c o o l l u x i n c a n d e s c e n t lamps R a d i a t i o n from a h e a t i n g element " R a d i a t i o n " from h o t w a t e r - b a t h . - 35 -i n c r e a s e i n f r u i t t e m p e r a t u r e w i t h d u r a t i o n was s i m i l a r a t a l l d e p t h s used i n t h e t r i a l . T h e r e was a s l i g h t d e c l i n e i n s u r f a c e t e m p e r a t u r e (depth 0 cm) a f t e r 1 hour e x p o s u r e t o t r e a t m e n t c o n d i t i o n . T h i s was p r o b a b l y due t o a c o m b i n a t i o n o f s k i n d e s i c c a t i o n and t h e r e s u l t a n t l o s s i n l a t e n t h e a t , and g r e a t e r h e a t exchange a t the s u r f a c e as a r e s u l t o f s k i n p u n c t u r e by t h e t h e r m o c o u p l e . I t t h u s became e v i d e n t t h a t d i f f e r e n t t y p e s o f r a d i a t i o n d i f f e r i n t h e i r a b i l i t y t o cause s u n s c a l d a t t h e same a i r t e m p e r a t u r e . A r t i f i c i a l l i g h t s o u r c e s were g e n e r a l l y more e f f e c t i v e t h a n o t h e r forms o f h e a t . The much r e d u c e d a b i l i t y o f water b a t h - f i l t e r e d r a d i a t i o n t o cause h e a t i n g ( T a b l e 6) s t r o n g l y s u g g e s t e d t h a t t h e i n f r a r e d r a d i a t i o n c o u l d be a f a c t o r c a u s i n g i n j u r y . A c c o r d i n g l y , i t was d e c i d e d t o i n v e s t i g a t e t h i s f a c t o r f u r t h e r . E f f e c t o f D i f f e r e n t Wavebands on I n j u r y Development The i n f r a r e d component o f t h e r a d i a t i o n from the a r t i f i c i a l l i g h t s o u r c e was i s o l a t e d u s i n g a CBS 750 IR f i l t e r and i t s e f f e c t s were compared w i t h the e f f e c t s o f b o t h v i s i b l e ' and f u l l r a d i a t i o n as w e l l as w i t h r a d i a t i o n from the h e a t i n g e l e m e n t . An a i r t e m p e r a t u r e o f 50°C was c h o s e n f o r a l l the t r e a t m e n t s m a i n l y t o improve t h e e f f e c t i v e n e s s o f t h e h e a t i n g e l e m e n t . - 86 -A l l t r e a t m e n t s p r o d u c e d i n j u r y a t 50°C (Table 7 ) , - 2 b u t t h e 500 W m i n f r a - r e d r a d i a t i o n was t h e most e f f e c t i v e . T r e a t m e n t s 3 and 4, i n w h i c h t h e i n f r a - r e d waveband was c u t o f f o r r e d u c e d , c a u s e d c o n s i d e r a b l y l e s s i n j u r y . A g a i n , m o i s t u r e l o s s was a s s o c i a t e d w i t h t h e i n j u r y and the g r e a t e s t w e i g h t l o s s o c c u r r e d i n the t r e a t m e n t t h a t p r o d u c e d the most s e v e r e i n j u r y . These r e s u l t s a g a i n s u g g e s t e d an i n f r a - r e d waveband e f f e c t . However, t h e r e was a l s o a s t r o n g t e m p e r a t u r e e f f e c t hence t h e i n f r a - r e d e f f e c t c o u l d n o t be i s o l a t e d . I t was, t h e r e f o r e , d e c i d e d t o c o n d u c t a n o t h e r t r i a l a t a l o w e r a i r •temperature u s i n g b o t h a r t i f i c i a l and n a t u r a l l i g h t s o u r c e s t o d e t e r m i n e t h e speed o f i n j u r y development under d i f f e r e n t wavebands. A t 40°C an i n f r a - r e d t r e a t m e n t w i t h an i r r a d i a n c e -2 o f 600 W m c a u s e d an i n j u r y s c o r e o f 2.0 t o be d e v e l o p e d i n f r u i t s w i t h i n 2.5 h o u r s o f e x p o s u r e ( T a b l e 8 ) . T h r e e h o u r s were r e q u i r e d w i t h f u l l - s p e c t r u m r a d i a t i o n and the f u l l s p e c t r u m r a d i a n t e n e r g y from t h e a r t i f i c i a l l i g h t s o u r c e was s l i g h t l y more e f f e c t i v e t h a n f u l l s p e c t r u m s o l a r r a d i a t i o n i n p r o d u c i n g a g i v e n l e v e l o f i n j u r y . Lower t e m p e r a t u r e s o r e l i m i n a t i o n o f t h e i n f r a - r e d waveband c o n s i d e r a b l y r e d u c e d the speed o f i n j u r y d e v e l o p m e n t . I t was, t h e r e f o r e , c o n c l u d e d t h a t t h e main f a c t o r r e s p o n s i b l e f o r t h e o c c u r r e n c e o f s u n s c a l d whenever f r u i t s a r e exposed t o s o l a r r a d i a t i o n was a s s o c i a t e d w i t h i n f r a - r e d r a d i a t i o n . - 87 -T a b l e 7. E f f e c t s o f D i f f e r e n t Wavebands on I n j u r y Development i n D e t a c h e d Tomato F r u i t s a t 50°C A i r T e m p e r a t u r e . T r e a t m e n t I r r a d i a n c e 3 Waveband M o i s t u r e L o s s I n j u r y (nm) (% f r e s h w t . ) 1. 500 W m 380-700 1.69 0.8 2. 500 W m~ 2 380-3000 6. 71 4.0 3. 500 W m~ 2 700-3000 8.23 4.8 4. H e a t i n g E l e m e n t Over 3000 3.92 2.5 5. C o n t r o l 23°C 0.35 a R a d i a t i o n was s u p p l i e d by 300 Watts PAR 56/2 MFL medium f l o o d , c o o l l u x i n c a n d e s c e n t lamps ( S y l v a n i a E l e c t r i c P r o d u t s I n c . , D e n v e r s , M a s s . , U . S . A . ) 1. -Radiant E n e r g y from lamps was f i l t e r e d by 8 cm deep c o l d w a t e r - b a t h . 2. U n f i l t e r e d R a d i a t i o n from l a m p s . 3. R a d i a t i o n from lamps was f i l t e r e d by a CBS 750 F a r - r e d f i l t e r . 4. R a d i a t i o n was s u p p l i e d by a H e a t i n g E l e m e n t A v e r a g e o f s c o r e s on s i x f r u i t s . F r u i t s were s c o r e d f o r i n j u r y i m m e d i a t e l y a f t e r a t r e a t m e n t p e r i o d o f 5 h o u r s . T a b l e 8. E f f e c t s o f R a d i a t i o n T r e a t m e n t ^ n t h e Speed o f I n j u r y Development i n D e t a c h e d Tomato F r u i t s a t 40 C A i r T e m p e r a t u r e s . R a d i a t i o n Treatment I r r a d i a n c e S o u r c e Wm -2 Waveband nm Temp. Time t o Development o f #2 I n j u r y * (hr) 1. C o o l beam l a m p s 3 600 380-700 - 40 10.0 2. C o o l beam lamps 600 380-3000 40 3.0 3. C o o l beam lamps 600 700-3000 40 2.5 4. S u n b - 600 380-3000 4 0 + 3 4 . 0 5. Sun 600 380-3000 22 10.0 6. C o n t r o l (Dark) 22 No I n j u r y * Average o f s c o r e s on s i x f r u i t s a 300 Watts PAR 56/2 MFL medium f l o o d , c o o l l u x i n c a n d e s c e n t lamps ( S y l v a n i a E l e c t r i c P r o d u c t s I n c . , D e n v e r s , M a s s . , U . S . A . ) b I r r a d i a n c e a t 12 noon J u l y 21, 1978 a t U . B . C . 1. R a d i a t i o n from lamps was f i l t e r e d by 8.0 cm deep c o l d w a t e r - b a t h . 2. U n f i l t e r e d r a d i a t i o n from l a m p s . 3. R a d i a t i o n from lamp was f i l t e r e d by a CBS 750 F a r - r e d f i l t e r . - 39 -E f f e c t s o f T e m p e r a t u r e T r e a t m e n t s A p p l i e d i n D a r k n e s s I t w i l l be r e c a l l e d t h a t a l l o f the t r i a l s r e p o r t e d so f a r a l s o showed s t r o n g t e m p e r a t u r e e f f e c t s . A c c o r d i n g l y , i t was d e c i d e d t o i n v e s t i g a t e t h e e f f e c t o f d i f f e r e n t t e m p e r a t u r e s i n t h e d a r k on t h e i n i t i a t i o n o f i n j u r y . T a b l e 9 shows t h a t i n j u r y can d e v e l o p i n d a r k n e s s under h i g h t e m p e r a t u r e c o n d i t i o n s and t h a t a g r e a t e r d e g r e e o f i n j u r y d e v e l o p s a t h i g h e r t e m p e r a t u r e s . M o i s t u r e l o s s a l s o i n c r e a s e d w i t h t e m p e r a t u r e . I t must be p o i n t e d o u t , however, t h a t v i s i b l e d i f f e r e n c e s were n o t e d between t h e t y p e o f i n j u r y p r o d u c e d by " t e m p e r a t u r e " and t h a t p r o d u c e d by " l i g h t " t r e a t m e n t s on g r e e n f r u i t s when t h e i n j u r y was a s s e s s e d i m m e d i a t e l y a f t e r t r e a t m e n t . The s u r f a c e c o l o u r o f tomato f r u i t s t r e a t e d w i t h h i g h t e m p e r a t u r e s i n d a r k n e s s was g r e y i s h . In c o n t r a s t , i n j u r e d f r u i t s p r o d u c e d under u n f i l t e r e d r a d i a n t energy from lamp s o u r c e s and t h e sun were w h i t i s h . However, t h e p r o g r e s s i o n o f i n j u r y f o l l o w i n g t r e a t m e n t was s i m i l a r i n b o t h i n j u r i e s and . t h e y c o u l d n o t be d i s t i n g u i s h e d from e a c h o t h e r a f t e r e i g h t days i n s t o r a g e . Hence, b o t h k i n d s o f i n j u r i e s were c o n s i d e r e d t o be e s s e n t i a l l y s i m i l a r . T r e a t m e n t s o f f r u i t s a t d i f f e r e n t t e m p e r a t u r e s and i r r a d i a n c e s were c a r r i e d ^ out f o r d i f f e r e n t d u r a t i o n s and were combined i n a f a c t o r i a l t r i a l . The t r i a l showed t h a t t h e e f f e c t s o f t e m p e r a t u r e and i r r a d i a n c e were a d d i t i v e and t h a t i n j u r y t e n d e d t o f o l l o w a d o s e - r e s p o n s e r e l a t i o n s h i p ( T a b l e 1 0 ) . T a b l e 9. E f f e c t s o f T e m p e r a t u r e T r e a t m e n t s A p p l i e d i n Darkness on I n j u r y Development. T e m p e r a t u r e ( ° C ) * M o i s t u r e L o s s (% w t ) * * I n j u r y * * 30 0.495 0.0 50 2.489 1.5 ± 1 70 5.505 3.8 + 1 C o n t r o l (20) 0.233 0.0 * H i g h t e m p e r a t u r e s were s u p p l i e d from h e a t i n g elements and were a p p l i e d u n i d i r e c t i o n a l l y t o the s t y l a r h a l f o f f r u i t s s i t t i n g s t y l a r - e n d up w i t h i n t r e a t m e n t chambers. * * V a l u e s a r e a v e r a g e s o f s c o r e s from s i x f r u i t s on a s c a l e o f 0 - 5 . F r u i t s were s c o r e d f o r i n j u r y i m m e d i a t e l y a f t e r 2 5 - h r . t r e a t m e n t d u r a t i o n . T a b l e 10. I n j u r y Development on Detached Tomato F r u i t s Exposed t o V a r y i n g C o m b i n a t i o n o f I r r a d i a n c e and Temperature f o r V a r y i n g T r e a t m e n t D u r a t i o n . I r r a d i a n c e * * D u r a t i o n Temperature (°C) (W m~ 2 ) (hr) 30 40 50 500 1 0 . 0 * 0. 0 0.6 + 3 0.0 0.3 2.3 5 0.0 0.6 4.0 650 1 0.0 0.3 1.3 3 0.0 1.6 2.6 5 0.6 2.3 4.3 750 1 0.0 1.0 2.6 3 0.6 2.6 4.6 5 1.6 3.6 5.0 * E a c h v a l u e i s an a v e r a g e o f 3 i n j u r y s c o r e s on a s c a l e o f 0 - 5 . * * F u l l ( u n f i l t e r e d ) r a d i a t i o n from 300 Watt 56 PAR/2 MFL medium f l o o d , c o o l l u x i n c a n d e s c e n t lamps. + S t a n d a r d d e v i a t i o n > + i n a l l c a s e s . - 92 -E f f e c t s o f 0 9 C o n c e n t r a t i o n D u r i n g R a d i a t i o n T r e a t m e n t I t has been shown t h a t c h l o r o p h y l l can be d e s t r o y e d i n g r e e n t i s s u e s by p h o t o o x i d a t i o n (Lomagin and A n t r o p o v a 1966). An e x p e r i m e n t was c a r r i e d out t o t e s t t h e i n v o l v e m e n t o f oxygen i n t h e o c c u r r e n c e o f s u n s c a l d i n j u r y . T a b l e 11 shows t h a t i n j u r y d e v e l o p e d a t a l l c o n c e n t r a t i o n s o f 0 2 u s e d . However, t h e c o l o u r o f t h e f r u i t s i r r a d i a t e d a t 0% 0 2 was g r e y i s h compared w i t h the c o l o u r o f f r u i t s i r r a d i a t e d a t e i t h e r 21% o r 100% 0,,. The r a t e o f f r u i t r e s p i r a t i o n i n c r e a s e d d u r i n g t r e a t m e n t up t o a maximum and t h e n f e l l . I t was much h i g h e r a t h i g h e r 0 2 l e v e l s t h a n a t 0% 0^ ( F i g u r e 9 ) . The r e s u l t s o f t h i s e x p e r i m e n t as w e l l as t h o s e o f t h e d a r k t e m p e r a t u r e t r e a t m e n t c o n c l u s i v e l y p r o v e d t h a t p h o t o o x i d a t i o n was n o t a major f a c t o r i n i n j u r y d e v e l o p m e n t . I n j u r y would d e v e l o p i n t h e l i g h t i n t h e absence o f 0 2 o r i n d a r k n e s s i n t h e p r e s e n c e o f 0^-Changes i n F o r c e - D e f o r m a t i o n C h a r a c t e r i s t i c s o f Tomato F r u i t s B o t h r e d u c e d and improved " f i r m n e s s " have been n o t e d i n tomato f r u i t s f o l l o w i n g e x p o s u r e t o s o l a r r a d i a t i o n ( H a l l 1964, S h e w f e l t 1970). I t i s n o t c l e a r , however, i f t h i s i n c o n s i s t e n c y i s due t o t h e method o f " f i r m n e s s " d e t e r m i n a t i o n o r i s s i m p l y t h e r e s u l t o f v a r i e t a l d i f f e r e n c e s as p o i n t e d out by H a l l (1964). T e x t u r a l q u a l i t y , and hence f r u i t f i r m n e s s , i n the tomato i s i n f l u e n c e d by f l e s h " f i r m n e s s " , t h e r a t i o between T a b l e 11. E f f e c t o f Oxygen C o n c e n t r a t i o n C u r i n g T r e a t m e n t on t h e Development o f I n j u r y and M a t u r e - G r e e n Tomato F r u i t s . T r e a t m e n t (a) I n j u r y S c o r e * C o l o r 0% 0 , 21% O, 100% O, 3.0 + 0.0 3.0 ± 0.0 3.0 + 0.0 G r e y i s h w h i t e White White T r e a t m e n t c o n s i s t e d o f a 5 - h o u r l o n g i r r a d i a t i o n w i t h u n f i l t e r e d r a d i a n t -2 energy 700 Wm from 300 Watts PAR 56/2 MFL medium f l o o d , c o o l l u x i n c a n d e s c e n t lamps a t chamber a i r - t e m p e r a t u r e o f 37+3°C Average o f two t r i a l s , 1 f r u i t p e r t r e a t m e n t . -94-« i 1 i i t ; i 0 15 30 4$ 60 75 90 105 . 120 T i m e m i n u t e s Figure 9. Effects of Oxygen Concentration on the Rate of Respiration of Detached Tomato Fruits During • Exposure to 64 0 V7 m~ Unfiltered Radiant Energy From 300 Watts PAR 56/2 MFL Medium Flood, Cool Lux Incandescent Sylvania Lamps: 0% 0-( *• ) ; 21% 0, ( • ); and 100% 0 2( • ). Chamber Temperature was 37+3 C During Treatment. - 95 -p e r i c a r p and l o c u l a r t i s s u e , and by s k i n t o u g h n e s s . S i x p h y s i c a l c h a r a c t e r i s t i c s d e s c r i b i n g a l l o f t h e above a s p e c t s were c a l c u l a t e d from a s i n g l e d e t e r m i n a t i o n f o r c e - d e f o r m a t i o n c u r v e as d e s c r i b e d i n M a t e r i a l s and Methods. The o b j e c t i v e s o f t h i s work were t o f i n d o u t (a) how d i f f e r e n t p o r t i o n s o f the f r u i t anatomy were a f f e c t e d and (b) w h i c h p h y s i c a l c h a r a c t e r i s t i c s were most r e s p o n s i v e t o s u n s c a l d - l i k e i n j u r y . T a b l e 12 summarizes t h e F v a l u e s and s i g n i f i c a n c e o f main e f f e c t s and i n t e r a c t i o n s i n t h e f o r c e - d e f o r m a t i o n r e s u l t s . F o r most o f t h e c h a r a c t e r i s t i c s measured, s i g n i f i c a n c e was o b t a i n e d f o r the main e f f e c t s o f r i p e n e s s , i n j u r y , s t o r a g e and p o s i t i o n as w e l l as f o r t h e i r i n t e r a c t i o n s . N e i t h e r t h e e f f e c t o f i n j u r y above, n o r t h e i n t e r a c t i o n between r i p e n e s s and i n j u r y , was s i g n i f i c a n t f o r mesocarp r e s i s t a n c e . B o t h r i p e n e s s and t h e i n t e r a c t i o n between r i p e n e s s and s t o r a g e d i d n o t s i g n i f i c a n t l y a f f e c t t o u g h n e s s . The i n t e r a c t i o n o f r i p e n e s s , i n j u r y and s t o r a g e was n o t s i g n i f i c a n t f o r d e f o r m a t i o n . F o r t h e o t h e r c h a r a c t e r i s t i c s , b o t h second and t h i r d l e v e l i n t e r a c t i o n s were s i g n i f i c a n t , b u t s i n c e my p r i m a r y i n t e r e s t was n o t on t h e s e h i g h e r i n t e r a c t i o n s , t h e t h i r d l e v e l i n t e r a c t i o n s were p o o l e d w i t h t h e e r r o r and the a n a l y s i s was r e p e a t e d . E f f e c t s o f F r u i t P o s i t i o n on F o r c e - D e f o r m a t i o n  C h a r a c t e r i s t i c s T h r e e f r u i t p o s i t i o n s : " s t y l a r " , " e q u a t o r i a l " , and " c a l y x " were demarcated and t h e f o r c e - d e f o r m a t i o n c h a r a c t e r i s t i c s were d e t e r m i n e d as d e s c r i b e d i n t h e M a t e r i a l s and M e t h o d s . The T a b l e 12. F V a l u e s and t h e S i g n i f i c a n c e o f Main E f f e c t s and i n t e r a c t i o n s on F o r c e - D e f o r m a t i o n C h a r a c t e r i s t i c s . F a c t o r s D e f o r m a t i o n P e r i c a r p S t r e n g t h Mesocarp R e s i s t a n c e C o m p l i a n c e F i r m n e s s Toughness R i p e n e s s I n j u r y S t o r a g e R. I R.S I . S R . I . S P o s i t i o n P.R P . I P.S P . R . I P . R . S P . I . S P . R . I . S 37.818 74.983 171.63 7. 030 6. 116 13.745 1.562 ns 235.25 15. 5 58.792 21.467 15.515 3.1450 8. 6869 5. 167 44.641 5. 267 149.59 3. 373 24. 46 16.035 4. 994 148.98 5.66 7. 365 32.791 15.242 7. 58 40.530 7.020 184.85 0.0513 ns 344.83 2.057 ns 88.802 16.630 7.116 2.4505 5. 6, 1227 9845 18.6730 2.6755 7.365 18.749 5.3412 185.40 82.981 922.11 6. 933 51.498 18. 07 8. 513 51.807 12.134 26.265 89.7 23.074 19.272 14.763 22. 62 378.82 40.146 1769.5 24.432 259.07 17.043 21.499 5.3390 36.225 71.010 6.539 14.287 38.507 7. 5721 E x c e p t where o t h e r w i s e s t a t e d , a l l v a l u e s were s i g n i f i c a n t a t P = 0.01. * s i g n i f i c a n t a t P = 0.05 ns n o t s i g n i f i c a n t 0.5229 ns 43.496 6.995* 5.955 0.9327 ns 17.694 3 . 0 8 5 * en 20.857 234.28 0.264 37.593 20.716 14.101 3.28 23.22 5.296 - 97 -e f f e c t o f f r u i t p o s i t i o n was s i g n i f i c a n t f o r many o f the c h a r a c t e r i s t i c s . The l o w e s t v a l u e s f o r d e f o r m a t i o n and p e r i c a r p s t r e n g t h were o b t a i n e d when measurements were made a t t h e c a l y x e n d . T h e r e was a s l i g h t i n c r e a s e i n d e f o r m a t i o n a t t h e e q u a t o r i a l r e g i o n o v e r t h e s t y l a r r e g i o n . Mesocarp r e s i s t a n c e showed a s t e a d y p o l a r d e c r e a s e i n v a l u e s from the s t y l a r end towards the c a l y x ( T a b l e 1 3 ) . However, s u c h d i f f e r e n c e s were n o t s i g n i f i c a n t a t t h e 1% p r o b a b i l i t y l e v e l . Toughness d e c r e a s e d s i g n i f i c a n t l y from the s t y l a r t o the c a l y x e n d . I n j u r y a l s o a f f e c t e d many o f the f o r c e - d e f o r m a t i o n c h a r a c t e r i s t i c s m e a s u r e d . B o t h d e f o r m a t i o n and t o u g h n e s s d e c r e a s e d s i g n i f i c a n t l y (P ^ 0 . 0 1 ) from the s t y l a r end t o the c a l y x r e g i o n . P e r i c a r p s t r e n g t h , mesocarp r e s i s t a n c e , c o m p l i a n c e and f i r m n e s s d i d n o t show such a t r e n d . Advanced i n j u r y d e c r e a s e d b o t h mesocarp r e s i s t a n c e and f i r m n e s s . The l o w e s t f i r m n e s s v a l u e s were o b t a i n e d a t the e q u a t o r i a l p o r t i o n o f t h e f r u i t . I t i s n o t e d however t h a t t h e e q u a t o r i a l r e g i o n o f t h e f r u i t w i t h advanced i n j u r y a l s o c o i n c i d e d w i t h the i n t e r f a c e between t h e i n j u r e d and u n i n j u r e d p o r t i o n s of the f r u i t . The e q u a t o r i a l r e g i o n had the h i g h e s t c o m p l i a n c e v a l u e s . I t would be r e c a l l e d from t h e M a t e r i a l s and Methods t h a t i n j u r y was always i n c u r r e d , by d e s i g n , a t t h e s t y l a r end o f the f r u i t s . The r e s u l t s p r e s e n t e d h e n c e f o r t h r e f e r o n l y t o measurements t a k e n a t one p o s i t i o n , t h e " s t y l a r " e n d . T a b l e 14 shows t h e p a r t i t i o n o f v a r i a t i o n i n t h e a n a l y s i s . T a b l e 13. E f f e c t s o f F r u i t P o s i t i o n on F o r c e - D e f o r m a t i o n C h a r a c t e r i s t i c s . I n j u r y P o s i t i o n D e f o r m a t i o n (mm) P e r i c a r p S t r e n g t h (g) Mesocarp R e s i s t a n c e (g) C o m p l i a n c e -1 -2 (mm g x l O ) F i r m n e s s (g mm ^) Toughness (g mm) 0 S t y l a r be 12.2 0 2 6 3 . 2d 2 9 . 2 7 a b 5 . 8 0 4 a 2 4 . 6 4 C 1 5 0 9 b E q u a t o r i a l 1 2 . 9 5 ° 226. 8 C 2 7 . 7 9 3 b 7 . 0 2 3 b 2 1 . 7 3 b 1 3 7 3 b C a l y x 1 0 . 6 4 a 1 9 7 . 7 b 2 5 . 4 2 a b 7 . 0 3 6 b 2 1 . 4 4 b 9 9 3 a 1 S t y l a r 1 4 . 4 5 d 2 5 0 . 5 d 3 3 . 9 2 b 6 . 2 0 5 3 1 8 . 5 5 b 1778 C E q u a t o r i a l 1 3 . 4 1 C 2 1 5 . 2 b c 2 8 . 6 5 a b 7 . 0 5 1 b 2 1 . 2 1 b 1341 b C a l y x 1 1 . 3 7 a b 1 7 2 . 3 a 2 1 . 4 0 a 7 . 7 5 6 ° 2 0 . 2 5 b 9 0 6 a °^  3 S t y l a r 22. 5 2 f 2 8 9 . 7 6 2 5 . 7 9 a b 8 . 6 0 6 d 1 4 . 6 0 a 3215 8 E q u a t o r i a l 1 8 . 7 5 S 2 1 4 . 6 b C 2 4 . 2 l a b 1 0 . 3 5 G 1 3 . 9 5 a 2 0 2 2 d C a l y x 1 3 . 2 6 C be 220.1 3 2 . 4 0b cd 8 . 1 3 0 c a 2 4 . 8 6C 1 2 6 8 b F i g u r e s i n t h e same column b e a r i n g t h e same l e t t e r d i d n o t d i f f e r s i g n i f i c a n t l y a c c o r d i n g t o S t u d e n t - N e w m a n - K e u l ' s t e s t (P = 0 . 0 1 ) . r T a b l e 14. An Example o f t h e A n a l y s i s o f V a r i a n c e f o r F o r c e - D e f o r m a t i o n C h a r a c t e r i s t i c s D e t e r m i n a t i o n t o I n d i c a t e the C o m p l e t e P a r t i t i o n o f V a r i a t i o n i n t h e A n a l y s i s : A n a l y s i s o f V a r i a n c e f o r F i r m n e s s . S o u r c e d f Sum o f S q . RUN 2 0 .34824 E-04 RIPENESS 3 0 .56592 -02 INJURY 2 0 .24569 -02 STORAGE 1 0 .52536 -02 R . I 6 0 .18022 -02 R.S 3 0 .26928 -02 I . S 2 0 .23056 -02 R . I . S 6 0 .21181 -02 ERROR (A) 46 0 .68328 - 0 3 ERROR 72 0 .51119 -04 TOTAL 143 _ .23058 -01 Mean S q . E r r o r F - v a l u e .17412 E-04 E r r o r (A) 1.1722** .18864 -02 1 2 7 . 0 0 * * .12285 -02 8 2 . 7 0 2 * * .52536 -02 3 5 3 . 6 8 * * .30037 -03 2 0 . 2 2 1 * * .89762 - 0 3 6 0 . 4 3 0 * * .11528 - 0 2 77.611** .35301 - 0 3 2 3 . 7 6 6 * * .14854 -04 2 0 . 9 2 1 * * .70999 - 0 6 S i g n i f i c a n t a t P = 0.01 - 100 -i E f f e c t s o f M a i n F a c t o r s : R i p e n e s s , I n j u r y and S t o r a g e on F o r c e - D e f o r m a t i o n C h a r a c t e r i s t i c s T a b l e 15 shows t h e e f f e c t o f r i p e n e s s , i n j u r y and s t o r a g e on f o r c e - d e f o r m a t i o n c h a r a c t e r i s t i c s o f tomato f r u i t s . F r u i t d e f o r m a t i o n and c o m p l i a n c e s i g n i f i c a n t l y i n c r e a s e d w i t h i n c r e a s i n g s t a g e o f r i p e n e s s , s t o r a g e and i n j u r y . A l t h o u g h t h e r e was an i n c r e a s e i n b o t h d e f o r m a t i o n and c o m p l i a n c e o f f r u i t s a t t h e t u r n i n g s t a g e o v e r t h e m a t u r e - g r e e n s t a g e . . the i n c r e a s e was n o t s i g n i f i c a n t a t t h e 1% p r o b a b i l i t y l e v e l . P e r i c a r p s t r e n g t h and f r u i t f i r m n e s s t e n d e d t o d e c r e a s e w i t h i n c r e a s i n g r i p e n e s s , s t o r a g e o r i n j u r y l e v e l s . Mesocarp r e s i s t a n c e d e c r e a s e d w i t h i n c r e a s i n g s t a g e o f r i p e n e s s and s t o r a g e b u t d i d n o t show a c l e a r p a t t e r n w i t h I n j u r y . Compared w i t h t h e u n i n j u r e d c o n t r o l s t h e r e was a q u a n t i t a t i v e i n c r e a s e i n mesocarp r e s i s t a n c e when i n j u r y was i n c i p i e n t and a d e c r e a s e when i n j u r y was a d v a n c e d . However, s u c h d i f f e r e n c e s were n o t s t a t i s t i c a l l y s i g n i f i c a n t a t 5% p r o b a b i l i t y l e v e l . B o t h r i p e n e s s and s t o r a g e had no s i g n i f i c a n t e f f e c t on f r u i t t o u g h n e s s , b u t t o u g h n e s s was s i g n i f i c a n t l y i n c r e a s e d by i n c r e a s i n g s e v e r i t y o f i n j u r y . E f f e c t s o f I n j u r y a t D i f f e r e n t Stages o f R i p e n e s s  on F o r c e - D e f o r m a t i o n C h a r a c t e r i s t i c s The e f f e c t s o f i n j u r y a t d i f f e r e n t s t a g e s o f r i p e n e s s on f o r c e - d e f o r m a t i o n c h a r a c t e r i s t i c s a r e shown i n F i g u r e 10. T a b l e 15. E f f e c t s o f M a i n F a c t o r s : R i p e n e s s , I n j u r y and S t o r a g e on F o r c e - D e f o r m a t i o n C h a r a c t e r i s t i c s . F a c t o r D e f o r m a t i o n (mm) P e r i c a r p S t r e n g t h '(g) Mesocarp R e s i s t a n c e (g) C o m p l i a n c e -1 -2 (mm g *10 ) F i r m n e s s (g mm ^) Toughness (g mm) R i p e n e s s 0 1 1 . 9 8 a 2 6 4 . 6 ° 4 9 . 9 0 d 6 . 0 1 8 a 2 6 . 5 6 ° 1581 ns 1 1 2 . 6 7 a 2 7 1 . 8 ° 3 9 . 5 5 ° 5 . 8 2 8 a 2 7 . 6 6 ° 1692 ns 3 1 4 . 8 8 b 2 0 4 . 0 b 1 3 . 4 3 b 7 . 7 0 7 b 1 6 . 5 0 b 1584 ns 5 1 8 . 0 4 ° 1 7 0 . 9 a 7 . 7 2 a 1 0 . 6 5 0 ° 9 . 7 6 a 1576 ns I n j u r y U n i n j u r e d 1 2 . 2 0 3 2 6 3 . 2 a b 29.27 ns 5 . 8 0 4 a 2 4 . 6 4 ° 1 5 0 9 a C o n t r o l 1 1 4 . 4 5 b 2 5 0 . 5 a 33.92 ns 6 . 2 0 5 3 1 8 . 5 5 b 1778 a 3 2 2 . 5 2 ° 2 8 9 . 7 b 25.70 ns 8 . 6 0 6 b 1 4 . 6 0 a 3 2 1 5 b S t o r a g e No S t o r a g e 1 1 . 4 9 3 2 7 2 . 3 b 4 1 . 5 1 b • 5 . 0 6 0 a 2 9 . 3 5 b 1487 ns S t o r a g e 1 7 . 3 0 b 1 8 3 . 3 a 1 3 . 7 9 3 1 0 . 0 4 0 b 1 0 . 9 2 a 1715 ns F i g u r e s b e a r i n g t h e same l e t t e r s w i t h i n the same f a c t o r and f o r c e - d e f o r m a t i o n c h a r a c t e r i s t i c , a r e n o t s t a t i s t i c a l l y d i f f e r e n t a c c o r d i n g t o t h e S t u d e n t - N e w m a n - K e u l ' s t e s t a t P = 0 . 0 1 . - 102 -301 E E c o 0J Q 10 J . 5 350h 6 D5 Q) U c re 5 0 h w L 175 30f-u o CO io»-F i g u r e 10, R i p e n e s s E f f e c t s o f I n j u r y a t D i f f e r e n t S t a g e s o f R i p e n e s s on F o r c e - D e f o r m a t i o n C h a r a c t e r i s t i c s . I n j u r y : 0 ( D ) , 1 ( A ) , 3 ( O ) . F i g u r e 10. ( C o n t ' d ) - 104 ~ I n j u r y i n c r e a s e d f r u i t d e f o r m a t i o n a t a l l s t a g e s o f r i p e n e s s and the i n c r e a s e became more p r o n o u n c e d a t s u c c e s s i v e r i p e n e s s s t a g e s . I n j u r y i n c r e a s e d p e r i c a r p f o r c e b u t the e f f e c t d i s a p p e a r e d a t h i g h e r s t a g e s o f r i p e n e s s . The s l i g h t q u a n t i t a t i v e i n c r e a s e i n p e r i c a r p f o r c e by u n i n j u r e d f r u i t s a t t h e t u r n i n g s t a g e o v e r t h e m a t u r e - g r e e n s t a g e was n o t s t a t i s t i c a l l y s i g n i f i c a n t . Mesocarp r e s i s t a n c e d e c r e a s e d w i t h r i p e n e s s b u t i n j u r y had no s i g n i f i c a n t e f f e c t on mesocarp r e s i s t a n c e . C o m p l i a n c e v a l u e s i n c r e a s e d w i t h i n c r e a s i n g r i p e n e s s . I n j u r y had no s i g n i f i c a n t e f f e c t on c o m p l i a n c e v a l u e s a t t h e m a t u r e - g r e e n s t a g e b u t t h e r e was a g e n e r a l i n c r e a s e i n c o m p l i a n c e v a l u e s due t o i n j u r y . T h i s i n c r e a s e became more p r o n o u n c e d a t h i g h e r s t a g e s o f r i p e n e s s . I n j u r y f u r t h e r r e d u c e d t h e d e c r e a s e d f i r m n e s s v a l u e s a s s o c i a t e d w i t h r i p e n e s s a t a l l s t a g e s o f r i p e n e s s . A l t h o u g h the e f f e c t o f r i p e n e s s on t o u g h n e s s was n o t s i g n i f i c a n t (Table 1 2 ) , the i n t e r a c t i o n between i n j u r y and r i p e n e s s was s i g n i f i c a n t . I n j u r y i n c r e a s e d t o u g h n e s s v a l u e s and t h e e f f e c t was g r e a t e s t d u r i n g the e a r l y s t a g e s o f r i p e n e s s . E f f e c t s o f S t o r a g e and I n j u r y on F o r c e - D e f o r m a t i o n  C h a r a c t e r i s t i c s F r u i t d e f o r m a t i o n i n c r e a s e d w i t h i n c r e a s i n g i n j u r y . S t o r a g e f u r t h e r enhanced t h e e f f e c t o f i n j u r y on d e f o r m a t i o n ( F i g u r e 11) . P e r i c a r p f o r c e and mesocarp r e s i s t a n c e d e c r e a s e d w i t h s t o r a g e b u t i n j u r y s u p p r e s s e d t h e r e d u c t i o n i n b o t h - 1 0 5 -30r* 20}-(C *oor 5 Or r-, In jury Figure 11. Effects of Storage and Injury on Force-Deformation Characteristics. No Storage ( Q ); Stored ( g ). - 106 ~ p e r i c a r p f o r c e and mesocarp r e s i s t a n c e a s s o c i a t e d w i t h s t o r a g e . C o m p l i a n c e v a l u e s i n c r e a s e d w i t h b o t h s t o r a g e and i n j u r y . A l t h o u g h i n j u r y d i d n o t appear t o have any e f f e c t on t h e p a t t e r n o f change i n c o m p l i a n c e v a l u e s , t h e i n c r e a s i n g c o m p l i a n c e v a l u e s a s s o c i a t e d w i t h s t o r a g e were f u r t h e r enhanced by i n j u r y . B o t h s t o r a g e and i n j u r y d e c r e a s e d f r u i t f i r m n e s s . However, t h e d r a s t i c d r o p i n f i r m n e s s v a l u e s a s s o c i a t e d w i t h s t o r a g e was r e d u c e d a t h i g h e r l e v e l s o f i n j u r y . I n j u r y i n c r e a s e d toughness v a l u e s and t h i s e f f e c t was more p r o n o u n c e d f o l l o w i n g s t o r a g e . E f f e c t o f R i p e n e s s , I n j u r y and S t o r a g e on Some C h e m i c a l C h a r a c t e r i s t i c s E f f e c t o f R i p e n e s s on P r o t o p e c t i n , A s c o r b i c A c i d and pH P r o t o p e c t i n c o n t e n t was measured as mg % a n h y d r o u r o n i c a c i d (AUA) and i t d r o p p e d from about 21 mg % AUA a t t h e m a t u r e - g r e e n s t a g e t o a b o u t 10 mg % AUA a t t h e r e d s t a g e ( F i g . 1 2 ) . T h i s change was g r a d u a l from t h e m a t u r e - g r e e n s t a g e (0) t o t h e p i n k s t a g e (3) o f r i p e n e s s b u t was s t e e p i between t h e p i n k and r e d s t a g e s . A s c o r b i c a c i d c o n t e n t i n c r e a s e d w i t h r i p e n e s s and i t r o s e from a b o u t 11 mg/100 g f r e s h w e i g h t i n mature g r e e n f r u i t s t o a b o u t 18 mg/100 g f r e s h w e i g h t i n r e d f r u i t s . T a b l e 16. F Values and t h e S i g n i f i c a n c e o f Main E f f e c t s and I n t e r a c t i o n s on P r o t o p e c t i n , A s c o r b i c A c i d and pH. C h e m i c a l C o n s t i t u e n t T r e a t m e n t E f f e c t P r o t o p e c t i n A s c o r b i c A c i d pH Run 0. 77 ns 0.15 ns 2.35 ns R i p e n e s s 42. 61 ** 167.89 ** 1.73 ns Injury- 369.78 * * 35. 67 ** 21.28 ** S t o r a g e 28. 09 ** 205.47 ** 76. 80 ** R x I 11.03 ** 8.52 ** 0.59 ns R x S 6.30 ** 19.69 ** 8.87 ** I x S 8.04 ** 34.85 ** 0. 51 ns R x I x S 1.50 ns 6. 85 ** 0.96 ns ns Not s i g n i f i c a n t ** S i g n i f i c a n t a t P = 0.01 - 108 -F i g u r e 12. E f f e c t s o f P r e - h a r v e s t R i p e n e s s on P r o t o p e c t i n C o n t e n t (mg % A U A ) , A s c o r b i c A c i d and p H . - 109 -There was no s i g n i f i c a n t change i n a s c o r b i c a c i d between the mature green and t u r n i n g stages of r i p e n e s s , but s i g n i f i c a n t changes o c c u r r e d a f t e r the t u r n i n g stage. There was a q u a n t i t a t i v e i n c r e a s e i n pH with advancing r i p e n e s s ( F i g . 12) but the i n c r e a s e was not s t a t i s t i c a l l y s i g n i f i c a n t (Table 16). E f f e c t of I n j u r y on P r o t o p e c t i n , A s c o r b i c A c i d and pH P r o t o p e c t i n content d i d not change wi t h m i l d i n j u r y but i n c r e a s e d s i g n i f i c a n t l y a t higher l e v e l s of i n j u r y (Fig.13). A s c o r b i c a c i d decreased s h a r p l y from about 22 mg/100 g f r e s h weight i n u n i n j u r e d f r u i t s t o about 5 mg/100 g f r e s h weight at the advanced i n j u r y stage. I n j u r y i n c r e a s e d pH va l u e s and the i n c r e a s e continued a t high e r l e v e l s of i n j u r y . E f f e c t s o f D i f f e r e n t L e v e l s of I n j u r y at V a r i o u s  Stages o f Ripeness P r o t o p e c t i n decreased with stage of r i p e n e s s at a l l l e v e l s o f i n j u r y ( F i g . 14a). There was a s t a t i s t i c a l l y s i g n i f i c a n t i n c r e a s e i n p r o t o p e c t i n due to i n j u r y a t the e a r l y stages o f r i p e n e s s but the i n c r e a s e disappeared a t the red stage where i n j u r y appeared t o f u r t h e r decrease p r o t o p e c t i n content. The i n c r e a s e i n p r o t o p e c t i n content o f f r u i t s having an i n c i p i e n t i n j u r y was not s i g n i f i c a n t l y d i f f e r e n t from the c o n t r o l at the 1% p r o b a b i l i t y l e v e l . -110-F i g u r e 13. E f f e c t s o f I n j u r y on P r o t o p e c t i n (mg % A U A ) , A s c o r b i c A c i d and p H . - I l l -2 5 2 0 < < E 15 10 r i p e n e s s F i g u r e 1 4 ( a ) . E f f e c t s o f I n j u r y a t D i f f e r e n t S t a g e s o f R i p e n e s s on P r o t o p e c t i n C o n t e n t : U n i n j u r e d C o n t r o l ( • ) , " i n c i p i e n t " I n j u r y ( A ) , "advanced" I n j u r y ( O ) . - 112 -Reduced a s c o r b i c a c i d c o n t e n t d e c r e a s e d w i t h i n j u r y b u t i n c r e a s e d w i t h r i p e n e s s ( F i g . 14b). I n j u r y d i d n o t appear t o a l t e r t h e p a t t e r n o f change i n a s c o r b i c a c i d due t o r i p e n e s s . pH g e n e r a l l y i n c r e a s e d w i t h i n j u r y a t a l l s t a g e s o f r i p e n e s s ( F i g . 1 4 c ) . Changes i n pH w i t h r i p e n e s s were f a i r l y s t e a d y i n u n i n j u r e d f r u i t s . In t h e p r e s e n c e o f i n j u r y , t h e r e was a s l i g h t d e c r e a s e i n pH a t t h e t u r n i n g s t a g e and t h e r e a f t e r r i p e n e s s had o n l y a s l i g h t e f f e c t on t h e i n c r e a s e d pH r e s u l t i n g from i n j u r y . In g e n e r a l , b o t h i n j u r y and r i p e n e s s between m a t u r e - g r e e n and f i r m r i p e s t a g e s d i d n o t p r o d u c e l a r g e changes i n p H . E f f e c t s o f S t o r a g e and I n j u r y on P r o t o p e c t i n . A s c o r b i c A c i d and pH P r o t o p e c t i n c o n t e n t d e c r e a s e d s i g n i f i c a n t l y f o l l o w i n g s t o r a g e b u t t h e s t o r a g e e f f e c t on p r o t o p e c t i n c o n t e n t d i s -a p p e a r e d w i t h i n c r e a s i n g s e v e r i t y o f i n j u r y ( F i g . 1 5 a ) . In t h e a b s e n c e o f s t o r a g e , i n j u r y d i d n o t have any s i g n i f i c a n t e f f e c t on p r o t o p e c t i n c o n t e n t . I n j u r y d e c r e a s e d the a s c o r b i c a c i d c o n t e n t o f tomato f r u i t s and t h e magnitude o f the d e c r e a s e depended on t h e s e v e r i t y o f i n j u r y . A s c o r b i c a c i d was i n c r e a s e d i n s t o r a g e b o t h i n t h e absence and p r e s e n c e o f i n j u r y but such an i n c r e a s e c o u l d n o t overcome t h e d r a s t i c r e d u c t i o n i n ' a s c o r b i c a c i d c o n t e n t b r o u g h t a b o u t by i n j u r y ( F i g u r e 15b). The pH o f tomato f r u i t s was i n c r e a s e d by b o t h s t o r a g e and i n j u r y - 113 -3 Of -25b CP o o \ E 2 0 — 1 5 ro I I I 0 1 3 R i pen es s F i g u r e 1 4 ( b ) . E f f e c t s o f I n j u r y a t D i f f e r e n t Stages o f R i p e n e s s on A s c o r b i c A c i d C o n t e n t : U n i n j u r e d C o n t r o l ( • ) , " i n c i p i e n t " I n j u r y (A ) , "advanced" I n j u r y ( O ) . -114-R i p e ne s s E f f e c t s o f I n j u r y a t D i f f e r e n t S t a g e s o f R i p e n e s s on p H : I n i n j u r e d C o n t r o l ( • ) , " i n c i p i e n t " I n j u r y ( A ) " a d v a n c e d " I n j u r y ( o ) . - 115 -- 116 -25 0 1 3 I n j u r y F i g u r e 15 ( b ) . E f f e c t s o f S t o r a g e and I n j u r y on A s c o r b i c A c i d C o n t e n t : No s t o r a g e ( j ~ j ) , s t o r e d ( - 117 ~ ( F i g u r e 1 5 c ) . The i n t e r a c t i o n between i n j u r y and s t o r a g e was n o t s i g n i f i c a n t ( T a b l e 1 6 ) . E f f e c t s o f I n j u r y a t D i f f e r e n t Stages o f R i p e n e s s  on t h e U l t i m a t e Lycopene C o n t e n t o f Tomato V i n e - r i p e tomatoes c . v . Vendor were i n i t i a l l y a n a l y z e d f o r Lycopene c o n t e n t a t a l l s t a g e s o f r i p e n e s s . I t was found t h a t Lycopene c o n t e n t i n c r e a s e d s t e a d i l y from t h e m a t u r e - g r e e n t o t h e o v e r - r i p e s t a g e o f r i p e n e s s ( F i g . 1 6 ) . Some l y c o p e n e , though a m i n u t e q u a n t i t y r was a l r e a d y p r e s e n t a t t h e m a t u r e - g r e e n s t a g e . Lycopene c o n t e n t was about 50 ug/g f r e s h w e i g h t a t t h e o v e r - r i p e s t a g e . F r u i t s were h a r v e s t e d a t v a r i o u s s t a g e s o f r i p e n e s s and t r e a t e d t o a c h i e v e d e s i r e d l e v e l s o f i n j u r y (see M a t e r i a l s and M e t h o d s ) . They were t h e n s t o r e d a t 22°C, 12 hour p h o t o p e r i o d u n t i l t h e y r e a c h e d t h e o v e r - r i p e s t a g e ( 6 ) . " U l t i m a t e Lycopene C o n t e n t " h e r e a f t e r w i l l r e f e r t o Lycopene c o n t e n t a t the o v e r -r i p e s t a g e . The i n i t i a l , p r e - s t o r a g e r i p e n e s s o f tomato f r u i t s d i d n o t s i g n i f i c a n t l y a l t e r t h e i r u l t i m a t e l y c o p e n e c o n t e n t ( F i g . 17) . The p r e s e n c e o f i n j u r y r e d u c e d t h e u l t i m a t e l y c o p e n e c o n t e n t . The d e c r e a s e i n l y c o p e n e c o n t e n t r e s u l t i n g from i n j u r y was e n l a r g e d by i n c r e a s i n g s e v e r i t y o f i n j u r y , b u t t h e m a j o r i t y o f t h e r e d u c t i o n i n l y c o p e n e due t o i n j u r y had a l r e a d y o c c u r r e d a t t h e s t a g e o f ' i n c i p i e n t " i n j u r y . Whenever i n j u r y o c c u r r e d , t h e h i g h e r t h e p r e - t r e a t m e n t r i p e n e s s , the h i g h e r t h e u l t i m a t e l y c o p e n e c o n t e n t . A t any s p e c i f i c s t a g e -118-P H I n j u r y F i g u r e 1 5 ( c ) . E f f e c t s o f S t o r a g e and I n j u r y on p H : No S t o r a g e ( Q ) , S t o r e d ( J | ) .. RIPENESS SCORE Lycopene C o n t e n t o f V i n e - R i p e Tomato F r u i t s a t V a r i o u s S t a g e s o f R i p e n e s s ; V e r t i c a l B a r s i n d i c a t e S t a n d a r d D e v i a t i o n Among T h r e e Measurements T a k e n p e r R i p e n e s s C a t e g o r y . - 120 ~ RIPENESS SCORE 17 F f f e c t s o f I n j u r y a t D i f f e r e n t Stages o f V i n e -F l g u r e 17. g ^ ^ f ^ J ^ U l t i m a t e Lycopene C o n t e n t Ul?xmate Lycopene C o n t e n t was D e t e r m i n e d as Lycopene C o n t e n t a t Stage 6 R i p e n e s s . - 121 _ r i p e n e s s , t h e r e was a s l i g h t b u t n o n - s i g n i f i c a n t d e c r e a s e i n l y c o p e n e c o n t e n t due t o i n j u r y . In g e n e r a l , t h e e f f e c t o f i n j u r y on l y c o p e n e d i d n o t a p p e a r t o be t h a t o f a c t u a l pigment d e c a y . The r e s u l t s a r e c o n s i s t e n t w i t h t h e d e s t r u c t i o n o f t h e mechanism o f pigment s y n t h e s i s as s u g g e s t e d by McCollum (1954) and V o g e l e (1937). P o s t - H a r v e s t R a t e s o f . R e s p i r a t i o n , E t h y l e n e P r o d u c t i o n and  M o i s t u r e L o s s o f Tomato F r u i t s I n j u r e d by D i r e c t E x p o s u r e s  t o R a d i a n t E n e r g y H a v i n g s t a n d a r d i z e d t h e t r e a t m e n t s as d e s c r i b e d i n t h e M a t e r i a l s and Methods, m a t u r e - g r e e n f r u i t s were i r r a d i a t e d f o r 1, 2 and 5 h o u r s , p r o d u c i n g c o r r e s p o n d i n g i n j u r y s c o r e s o f •< 1 (not d e t e c t a b l e a f t e r t r e a t m e n t ) 1.0 and 3 . 0 w h i c h w i l l b e , r e s p e c t i v e l y , r e f e r r e d t o as " i n d u c t i o n " , " i n c i p i e n t " and "advanced" t y p e s o f i n j u r y h e r e a f t e r ( F i g . 1 8 ) . M o i s t u r e l o s s and r a t e s o f CC>2 and C^H^ p r o d u c t i o n were d e t e r m i n e d d a i l y (see M a t e r i a l s and Methods) u n t i l f r u i t s r e a c h e d the o v e r -r i p e s t a g e . Rate o f R e s p i r a t i o n In g e n e r a l , t h e c l i m a c t e r i c peak was a t t a i n e d w i t h i n t h r e e days a f t e r h a r v e s t ( F i g . 1 9 ) . The r a t e o f r e s p i r a t i o n was i n i t i a l l y enhanced b y t r e a t m e n t s t h a t p r o d u c e d " i n d u c t i o n " s t a g e i n j u r y . I n j u r y o f b o t h the " i n d u c t i o n " and " i n c i p i e n t " t y p e s a c c e l e r a t e d t h e o c c u r r e n c e o f t h e c l i m a c t e r i c peak more Untreated Induction (not d e t e c t a b l e a f t e r treatment) I n c i p i e n t Advanced 18. Photographs of Tomato F r u i t s with the "Induction" " i n c i p i e n t " and "advanced" Types of In j u r y , 8 Day Fol l o w i n g Treatments. F r u i t s were Exposed to 680 W m-2 U n f i l t e r e d R a d i a t i o n at 40°C f o r 0, 1, 2 or 5 Hours R e s p e c t i v e l y . -123-Treatment F i g u r e 19. P o s t - T r e a t m e n t Rate o f R e s p i r a t i o n o f D e t a c h e d Tomato F r u i t s a t V a r i o u s S t a g e s o f I n j u r y : U n i n j u r e d C o n t r o l , 0 ( O ) ; " i n d u c t i o n " i n j u r y , <. 1 ( A ) ; " i n c i p i e n t ' ' I n j u r y , " a d v a n c e d " I n j u r y , 3 ( • ) . 1 ( • ) ; • a n d - 124 -t h a n the c o n t r o l . Advanced i n j u r y r e d u c e d t h e r a t e o f r e s p i r a t i o n t h r o u g h o u t t h e measurement p e r i o d . I n d u c t i o n l e v e l i n j u r y a f f e c t e d t h e c l i m a c t e r i c by i n c r e a s i n g the s l o p e o f t h e c l i m a c t e r i c r i s e o f r e s p i r a t i o n w h i l e advanced i n j u r y d e c r e a s e d t h e s l o p e . D i f f e r e n c e s i n t h e r a t e o f CC^ p r o d u c t i o n ' between t r e a t m e n t s were much r e d u c e d i n the p o s t c l i m a c t e r i c peak p e r i o d . I t m i g h t be c o n c l u d e d t h a t the e f f e c t s o f i n j u r y on t h e r a t e o f r e s p i r a t i o n a r e more e v i d e n t i n the e a r l y t o m i d d l e c l i m a c t e r i c p e r i o d s . Once t h e s e s t a g e s have been p a s s e d , d i f f e r e n c e s i n t h e v a r i o u s i n j u r y l e v e l s on the b a s i s o f r a t e o f r e s p i r a t i o n a r e l e s s e v i d e n t . Rate of E t h y l e n e P r o d u c t i o n The i n i t i a l r a t e s o f e t h y l e n e p r o d u c t i o n were n o t much d i f f e r e n t i n t h e i n j u r e d and u n i n j u r e d f r u i t s ( F i g u r e 2 0 ) . However, a f t e r t h e peak o f e t h y l e n e p r o d u c t i o n had been r e a c h e d J , e t h y l e n e p r o d u c t i o n i n t h e i n j u r e d f r u i t s c o n t i n u e d a t a h i g h e r r a t e t h a n i n t h e c o n t r o l s . F r u i t s w i t h advanced i n j u r y had t h e h i g h e s t r a t e o f p o s t - p e a k e t h y l e n e p r o d u c t i o n . The peak o f e t h y l e n e p r o d u c t i o n was r e a c h e d one day e a r l i e r i n f r u i t s w i t h t h e " i n d u c t i o n " and " i n c i p i e n t " t y p e s o f i n j u r y . The p a t t e r n o f e t h y l e n e p r o d u c t i o n i n a l l t r e a t m e n t s was a s i g m o i d and t h i s was i n agreement w i t h t h e f i n d i n g o f Workman and P r a t t (1957). -125-1 2 3 4 5 6 7 8 Days a f t e r T r ea tmen t F i g u r e 20. P o s t - T r e a t m e n t Rate o f E t h y l e n e P r o d u c t i o n o f D e t a c h e d Tomato F r u i t s a t V a r i o u s S t a g e s o f I n j u r y : U n i n j u r e d C o n t r o l , 0 ( O ) ; " i n d u c t i o n " I n j u r y , «<1 1 ( A ) ; " i n c i p i e n t " I n j u r y , 1 ( • ) ; and " a d v a n c e d " I n j u r y , 3 ( • ) . - 126 -F i g u r e 21 shows t h e r e l a t i o n s h i p between the c l i m a c t e r i c and t h e r a t e o f e t h y l e n e p r o d u c t i o n . In a l l c a s e s , t h e c l i m a c t e r i c p r e c e d e d t h e peak o f e t h y l e n e p r o d u c t i o n by a b o u t two d a y s . Ai h i g h e r p r o p o r t i o n a t e r a t e o f e t h y l e n e p r o d u c t i o n r e l a t i v e t o t h e r a t e o f r e s p i r a t i o n was o b s e r v e d i n i n j u r e d f r u i t s . The r a t e o f r e s p i r a t i o n was a l r e a d y s u b s t a n t i a l a t t h e m a t u r e - g r e e n s t a g e s i n c e t h i s was an o n - g o i n g p r o c e s s , and t h e peak o f t h e r e s p i r a t o r y c l i m a c t e r i c was r e a c h e d a t t h e p i n k s t a g e o f r i p e n e s s . On the o t h e r hand, p r o d u c t i o n o f m e a s u r a b l e q u a n t i t i e s o f e t h y l e n e began w i t h the f i r s t a p p e a r a n c e o f c o l o u r about t h e o n s e t o f the c l i m a c t e r i c , and i t r e a c h e d a peak a t the f i r m - r i p e s t a g e . M o i s t u r e L o s s I n j u r y i n c r e a s e d m o i s t u r e l o s s and the m a g n i t u d e o f the e f f e c t i n c r e a s e d w i t h t h e s e v e r i t y o f i n j u r y . However, t h e i n c r e a s e d m o i s t u r e l o s s was s u b s t a n t i a l o n l y d u r i n g t h e t r e a t m e n t p e r i o d ( F i g u r e 2 2 ) . The a p p a r e n t p o s t - t r e a t m e n t r a t e o f m o i s t u r e l o s s was a p p r o x i m a t e l y c o n s t a n t f o r each t r e a t m e n t t h r o u g h o u t the s t o r a g e p e r i o d . A c o n s i s t e n t l y h i g h e r m o i s t u r e l o s s was found i n t h e i n j u r e d f r u i t s d u r i n g s t o r a g e . -127-Uninjured Injury < 1 ? i 6 1X1 ce Injury = 1 1 2 3 4 5 6 7 8 Injury = 3 1 2 3 4 5 6 7 8 o o a o cc Q. LU - J >-X h-LU TIME, days F i g u r e 2 1 . D a y s a f t e r ( r e a t m e n t F i g u r e 22. P o s t - T r e a t m e n t M o i s t u r e L o s s o f Detached Tomato F r u i t s a t V a r i o u s Stages o f I n j u r y : U n i n j u r e d C o n t r o l , 0 ( Q ) ; " i n d u c t i o n " - * ! 1 ( " i n c i p i e n t " , 1 ( ^ ) ; and " a d v a n c e d " , 3( | | | ) . - 129 -C o n t r o l o f I n j u r y S t o r a g e t r e a t m e n t s e m p l o y i n g v a r i o u s l i g h t o r d a r k c o n d i t i o n s as w e l l as exposure o f i n j u r e d f r u i t s t o a 100% 0^ a t m o s p h e r e , were n o t e f f e c t i v e i n a l l e v i a t i n g the i n j u r y ( T a b l e 17a). In a l l t r e a t m e n t s i n j u r i e s t h a t were n o t d e t e c t a b l e i m m e d i a t e l y a f t e r exposure t o r a d i a n t energy became n o t i c e a b l e f o l l o w i n g r i p e n i n g i r r e s p e c t i v e o f t h e p h o t o p e r i o d and t e m p e r a t u r e regime d u r i n g s t o r a g e . In a n o t h e r t r i a l , e f f o r t s were made t o d e l a y the r i p e n i n g o f t h e u n i n j u r e d f r u i t p o r t i o n s w h i l e t h e i n j u r e d p a r t s were exposed t o c o n d i t i o n s t h a t a r e known t o a c c e l e r a t e r i p e n i n g ( i . e . l i g h t , optimum t e m p e r a t u r e and 0^). No t r e a t m e n t was a b l e t o r e d u c e t h e i n j u r y ( T a b l e 17b). A t t h i s p o i n t , t h i s s e c t i o n o f t h e s t u d y was t e r m i n a t e d as i t became c l e a r t h a t t h e i n j u r y was permanent and p r a c t i c a l p o s t - h a r v e s t t r e a t m e n t s known t o r e g u l a t e r i p e n i n g were n o t a b l e t o r e v e r s e t h e i n j u r y . T a b l e 17(a) E f f e c t s o f D a r k n e s s , L i g h t o r Oxygen Treatments D u r i n g S t o r a g e on A l l e v i a t i o n o f I n j u r y i n Tomato F r u i t s I n j u r e d by Exposure t o I n t e n s e R a d i a n t E n e r g y . T r e a t m e n t Temp. POST-TREATMENT INJURED FRUITS I n i t i a l I n j u r y # F r u i t s W i t h # F r u i t s W i t h D e t e c t a b l e I n j u r y * I n j u r y 2* F i n a l I n j u r y # F r u i t s W i t h # F r u i t s W i t h D e t e c t a b l e I n j u r y I n j u r y 2 1. Dark c o o l 2. Dark warm 3. L i g h t (12 h r / d a y ) 10°C 2 2°C 10°C 10 10 10 6 9 7 10 10 10 o , L i g h t (12 h r / d a y ) , L i g h t (24 h r / d a y ) , 100% 0 « , L i g h t (12 h r / d a y ) 2 2°C 2 2°C 2 2 ° C * * 10 10 10 10 10 * F r u i t s were exposed t o r a d i a n t energy and s o r t e d i n t o two c a t e g o r i e s : o f u n d e t e c t a b l e I n j u r y and I n j u r y s c o r e ^ . 2 . 0 . Ten f r u i t s o f each c a t e g o r y were kept under v a r i o u s s t o r a g e c o n d i t i o n s f o r 2 weeks d u r i n g w h i c h they were i n s p e c t e d f o r l o s s o r appearance o f i n j u r y . S c o r e s were f i n a l s c o r e s a t the end o f s t o r a g e p e r i o d . * * O n l y 6 f r u i t s p e r c a t e g o r y were s t o r e d i n 0^. T r e a t m e n t l a s t e d 8 d a y s . T a b l e 1 7 ( b ) . E f f e c t o f P a r t i a l o r T o t a l B l a c k P l a s t i c Wrapping of I n j u r e d Tomato F r u i t s D u r i n g S t o r a g e Exposure t o L i g h t o r Oxygen, on I n j u r y . 1. 5 0% w r a p p i n g 21% 0 2 , 12 h r / d a y l i g h t 25°C 100% w r a p p i n g 2 5°C 3. 50% w r a p p i n g 100% 0 2 , 12 h r / d a y l i g h t 25°C No w r a p p i n g Dark 25°C INJURED FRUITS F r u i t A r e a Wrapped Temp. I n i t i a l F i n a l F r u i t s w i t h advanced i n j u r y were s e l e c t e d and e i t h e r wrapped i n u n a f f e c t e d c a l y x h a l f (50% w r a p p i n g ) , o r t o t a l l y wrapped (100% wrapping) o r unwrapped w i t h d o u b l e l a y e r o f b l a c k p o l y e t h y l e n e s h e e t s kept i n p l a c e by s c o t c h t a p e . T h e r e were 6 f r u i t s p e r t r e a t m e n t e x c e p t t r e a t m e n t 3 w i t h 3 f r u i t s . - 132 -DISCUSSION C h a r a c t e r i z a t i o n o f F a c t o r s C a u s i n g I n j u r y In t h e f i r s t p a r t o f t h i s s t u d y , t h e main f a c t o r s c a u s i n g i n j u r y o f d e t a c h e d tomato f r u i t by d i r e c t e x p o s u r e t o r a d i a n t energy were i n v e s t i g a t e d . The r e s u l t s c l e a r l y d e m o n s t r a t e t h a t s u n s c a l d - l i k e i n j u r y o f tomato f r u i t s can be c a u s e d by t r e a t m e n t w i t h h i g h i r r a d i a n c e s from a r t i f i c i a l l i g h t s o u r c e s as w e l l as from t h e s u n . These r e s u l t s a r e i n g e n e r a l agreement w i t h t h e f i n d i n g s o f Ramsey (19 30) on o n i o n s , L e C l e r g e (1931) on melons and w i t h t h e works o f Cook (1921), R e t i g and Kedar (1967) and L i p t o n (1970) on t o m a t o e s . L i p t o n (1970) s u g g e s t e d t h a t the i n c i d e n c e o f c o l o u r d e f e c t s i n r i p e tomato f r u i t s grown i n t h e g r e e n h o u s e was due t o " i n f r a - r e d and s h o r t - w a v e " r a d i a t i o n . H i s c o n c l u s i o n was b a s e d on t h e f a c t t h a t among t h e unshaded f r u i t s i n h i s t r i a l s , t h e u n p a i n t e d f r u i t s and f r u i t s p a i n t e d b l a c k had h i g h e r i n c i d e n c e o f " s o l a r y e l l o w i n g " t h a n t h o s e p a i n t e d w h i t e . On t h e c o n t r a r y , R e t i g and Kedar (1967) exposed d e t a c h e d tomato f r u i t s t o d i r e c t s o l a r r a d i a t i o n and c o n c l u d e d t h a t "heat a p p e a r s t o be t h e main e x t e r n a l f a c t o r c a u s i n g s u n s c a l d i n t o m a t o " . The p r e s e n t s t u d y has e x t e n d e d b o t h R e t i g / K e d a r 1 s and L i p t o n ' s work by i n v e s t i g a t i n g f a c t o r s w h i c h i n c l u d e d a c t u a l a p p l i c a t i o n o f i n f r a - r e d r a d i a t i o n and h e a t s e p a r a t e l y . The r e s u l t s d e m o n s t r a t e t h a t d i f f e r e n c e s i n t h e s e v e r i t y o f i n j u r y - 133 -induced by the v a r i o u s treatments can i n p a r t be r e l a t e d to the t o t a l r a d i a t i o n a p p l i e d i n the i n f r a - r e d r e g i o n of the spectrum and to the h i g h temperatures developed w i t h i n the f r u i t s . The f o l l o w i n g d i s c u s s i o n w i l l attempt to assess the r e l a t i v e c o n t r i b u t i o n s of i n f r a - r e d r a d i a t i o n and temperature. I n f r a - r e d R a d i a t i o n In the t r i a l which e v a l u a t e d the e f f e c t i v e n e s s of d i f f e r e n t sources of r a d i a t i o n i n c a u s i n g i n j u r y ( F i g . 7 ) , the u n f i l t e r e d r a d i a t i o n from incandescent S y l v a n i a lamps (LUR), contained the g r e a t e s t amount of energy i n the i n f r a - r e d . The r a d i a t i o n from hot water-bath (HWR) and h e a t i n g element (HER) treatments were long-wave r a d i a t i o n . S i m i l a r l y i n the LWR treatment, the p r o p o r t i o n of v i s i b l e r a d i a t i o n i n the t o t a l r a d i a t i o n r e c e i v e d a t the f r u i t s u r f a c e , was enhanced a t the expense of the i n f r a - r e d r a d i a t i o n by p a s s i n g the r a d i a t i o n through a water-bath. Water absorbs much of the i n f r a - r e d r a d i a t i o n a t wavelengths longer than 900 nm and hence i s o f t e n used as a f i l t e r i n p h o t o b i o l o g i c a l experiments where the main i n t e r e s t s are i n r a d i a t i o n a t s h o r t e r wavelengths. In none o f the t r i a l s i n the absence of a p p r e c i a b l e i n f r a - r e d r a d i a t i o n was i n j u r y developed a t temperatures below 50°C w i t h i n a 3-hour treatment p e r i o d . Where i n f r a - r e d r a d i a t i o n was abundantly s u p p l i e d by the lamps, i t produced the most severe i n j u r y per u n i t d u r a t i o n of treatment, or i t produced - 134 ~ a s p e c i f i e d i n j u r y s c o r e i n a minimum t r e a t m e n t d u r a t i o n ( T a b l e 8 ) . Normal i n c a n d e s c e n t lamps, such as t h e medium f l o o d c o o l l u x S y l v a n i a lamps, have w a v e l e n g t h s o f peak e m i t t a n c e i n t h e i n f r a - r e d a c c o r d i n g t o W i e n 1 s d i s p l a c e m e n t law. They a l s o have a g r e a t e r p r o p o r t i o n o f i n f r a - r e d r a d i a t i o n r e l a t i v e t o t h e t o t a l energy e m i t t e d than does t h e sun ( B i c k f o r d and Dunn 1972). T h i s p r o b a b l y a c c o u n t s f o r the g r e a t e r speed o f i n j u r y development under r a d i a t i o n from the i n c a n d e s c e n t S y l v a n i a lamps compared w i t h t h e e f f e c t s o f the sun (Table 8 ) . D u r i n g t h e p r e s e n t i n v e s t i g a t i o n s , t h e maximum t o t a l i n j u r y e v e r o b s e r v e d was p r o d u c e d when f r u i t s were i r r a d i a t e d w i t h 500 W m i n f r a - r e d r a d i a t i o n a t 50°C a i r t e m p e r a t u r e f o r 5 - h o u r t r e a t m e n t d u r a t i o n . A g a i n , as i n p r e v i o u s e x p e r i m e n t s , t r e a t m e n t s w i t h s i m i l a r i r r a d i a n c e s o f v i s i b l e r a d i a t i o n o r t r e a t m e n t s a t h i g h a i r t e m p e r a t u r e s p r o d u c e d i n j u r y t o l e s s e r d e g r e e s ( T a b l e 7 ) . I n f r a - r e d r a d i a t i o n o f t h e m a g n i t u d e s employed i n t h i s e x p e r i m e n t can be e n c o u n t e r e d i n n a t u r a l -2 s i t u a t i o n s . Maximum i r r a d i a n c e s o f o v e r 1000 W m a t s o l a r noon o f t e n o c c u r i n t r o p i c a l and s u b - t r o p i c a l r e g i o n s on c l o u d l e s s days ( M o n t e i t h 1973). Peak s o l a r i r r a d i a n c e s o f -2 100 0 W m a t sea l e v e l i n t e m p e r a t e r e g i o n s have a l s o been r e c o r d e d i n t h e midsummer ( B i c k f o r d and Dunn 1972). About 40% o f t h e t o t a l r a d i a t i o n r e c e i v e d a t t h e e a r t h ' s s u r f a c e i s i n t h e i n f r a - r e d (Gates 1963). However, an a i r t e m p e r a t u r e o f 50°C i s n o t n o r m a l f o r tomato g r o w i n g r e g i o n s , a l t h o u g h s o i l t e m p e r a t u r e s o f o v e r 50°C have been r e c o r d e d ( G e i g e r 1959). - 135 -In many o f t h e t r i a l s , t h e t o t a l r a d i a t i o n i n c i d e n t on t h e f r u i t s u r f a c e was e q u a l i n t h e " i n f r a - r e d " and " v i s i b l e " p o r t i o n o f t h e s p e c t r u m ( T a b l e s 7 and 8 ) . T h i s does not mean, however, t h a t e q u a l energy was a b s o r b e d by the f r u i t s . I t has been shown t h a t b o t h r e f l e c t a n c e and t r a n s m i t t a n c e by p l a n t s u r f a c e s a r e n o t a p p r e c i a b l e ( u s u a l l y l e s s t h a n 10%) i n the v i s i b l e r e g i o n o f t h e s p e c t r u m , a r e c o n s i d e r a b l e (30-58%) i n t h e n e a r i n f r a - r e d r e g i o n , and a g a i n a r e much r e d u c e d a t w a v e l e n g t h s beyond 1500 nm. S i m i l a r l y , a b s o r b a n c e i s m i n i m a l i n t h e n e a r i n f r a - r e d 730-1400 nm, b u t i s o v e r 90% i n t h e v i s i b l e and t h e l o n g e r i n f r a - r e d r e g i o n s (Gates 1965). I t i s t o be e x p e c t e d , t h e r e f o r e , t h a t t h e amount o f r a d i a n t energy " r e t a i n e d " by t h e f r u i t t i s s u e s was h i g h e r i n t h e v i s i b l e r e g i o n t h a n i n t h e n e a r i n f r a - r e d r e g i o n o f t h e s p e c t r u m . Yet i t was the i n f r a - r e d t r e a t m e n t t h a t p r o d u c e d g r e a t e s t d e g r e e o f i n j u r y . I t i s known t h a t most o f t h e energy i n v i s i b l e r a d i a t i o n i s p h o t o s y n t h e t i c a l l y a c t i v e . S i n c e m a t u r e - g r e e n f r u i t s were u s e d i n many o f t h e s e t r i a l s , i t can be a r g u e d t h a t a s i g n i f i c a n t p r o p o r t i o n o f t h e v i s i b l e r a d i a t i o n s u p p l i e d m i g h t have been d i v e r t e d t o p h o t o s y h t h e t i c energy t r a n s f e r p r o c e s s e s a t t h e expense o f r e a c t i o n s r e l a t e d t o i n j u r y d e v e l o p m e n t . However, t h e r e s u l t o f a r e p e a t t r i a l u s i n g f r u i t s a t the p i n k s t a g e o f r i p e n e s s showed t h a t t h e e f f e c t i v e n e s s o f v i s i b l e r a d i a t i o n i n c a u s i n g i n j u r y was not - 136 -enhanced by the absence o f g r e e n t i s s u e s . I n j u r y was a l s o d e v e l o p e d on p i n k f r u i t s by t r e a t m e n t s w h i c h d i d n o t e x c l u d e i n f r a - r e d r a d i a t i o n ( F i g . 23 ) . T h i s shows, t h e r e f o r e , t h a t t h e amount o f energy d i v e r t e d t o p h o t o s y n t h e t i c energy t r a n s f e r p r o c e s s e s i s n o t enough t o a c c o u n t f o r t h e d i f f e r e n c e s i n t h e e f f e c t i v e n e s s o f v i s i b l e and i n f r a - r e d r a d i a t i o n . A n o t h e r f a c t o r t h a t m i g h t have been r e s p o n s i b l e f o r the l e s s e r e f f e c t i v e n e s s o f v i s i b l e r a d i a t i o n , compared w i t h i n f r a - r e d r a d i a t i o n , i s t h e s e n s i t i v i t y o f t h e K e t t e r i n g YS1 r a d i o m e t e r u s e d t o d e t e r m i n e t h e i r r a d i a n c e s . The r a d i o m e t e r had a s i l i c o n s e n s o r w i t h a l o n g wave c u t - o f f p o i n t a t 2,500 nm. A l t h o u g h r a d i a n t energy beyond 2,500 nm from t h e 300 W i n c a n d e s c e n t s y l v a n i a lamps was l e s s t h a n 5% o f t h e t o t a l i n c i d e n t s p e c t r a l e n e r g y , t h e i r r a d i a n c e s measured i n t h e i n f r a - r e d were n o n e t h e l e s s u n d e r - e s t i m a t e d by t h e r a d i o m e t e r . T h i s u n d e r e s t i m a t i o n o f t h e q u a n t i t y o f i n f r a - r e d r a d i a t i o n i n a d d i t i o n t o a f u r t h e r d e p l e t i o n o f t h e " e f f e c t i v e " v i s i b l e r a d i a t i o n t h r o u g h d i v e r s i o n t o p h o t o s y n t h e t i c e n e r g y - t r a n s f e r p r o c e s s e s may a c c o u n t f o r t h e c o n s i s t e n t l y g r e a t e r i n j u r y development under i n f r a - r e d r a d i a t i o n r e p o r t e d i n the p r e s e n t s t u d y . The i n v o l v e m e n t o f i n f r a - r e d r a d i a t i o n i n i n j u r y development was p u r s u e d f u r t h e r t h r o u g h measurements o f the a b s o r p t i o n s p e c t r a o f tomato f r u i t s t i s s u e s . The d e t e r m i n a t i o n o f i n f r a - r e d a b s o r p t i o n s p e c t r a d i d n o t i n d i c a t e any major peaks o r t r o u g h s i n a b s o r b a n c e by t h e f r e e z e - d r i e d t i s s u e ( F i g s . 2 4 a , b ) . - 137 -F i g u r e 23. Photograph of a Tomato F r u i t at the Pink-red Stage o f Ripeness, I r r a d i a t e d w i t h a 600 W m U n f i l t e r e d R a d i a t i o n from Incandescent S y l v a n i a Lamps at 40 C f o r 5 Hours. -13S -A t r o u g h a t 1900 nm was c o n s i s t e n t l y p r e s e n t i n the d e t e r m i n a t i o n s when c h l o r o f o r m was used as t h e s o l v e n t ( F i g . 2 4 a ) . But t h e c a u s e o f t h i s t r o u g h c o u l d n o t be i d e n t i f i e d on the b a s i s o f t h e r e s u l t s o b t a i n e d . T h e r e f o r e , no e v i d e n c e has been o b t a i n e d , from t h i s s t u d y t o i n d i c a t e t h a t t h e i n v o l v e m e n t o f t h e n e a r i n f r a - r e d waveband i n t h e development o f s u n s c a l d - l i k e i n j u r y on d e t a c h e d tomato f r u i t s depends on a s p e c i a l c h r o m o p h o r i c s y s t e m w i t h i n t h e f r u i t s . H i g h T e m p e r a t u r e s I t w i l l be r e c a l l e d from the r e s u l t s w h i c h d e a l t w i t h t h e e f f e c t i v e n e s s o f v a r i o u s t y p e s o f r a d i a t i o n i n c a u s i n g i n j u r y , t h a t f r u i t t e m p e r a t u r e s i n a l l t r e a t m e n t s were h i g h e r t h a n a i r t e m p e r a t u r e s ( F i g . 8 a ) . I t has been shown t h a t f r u i t t e m p e r a t u r e s i n t h e f i e l d c a n r i s e s i g n i f i c a n t l y above a i r t e m p e r a t u r e s ( H a l l 1964, M c G i l l i v r a y 1934, S c h r o e d e r 1965). The magnitude o f t h e i n c r e a s e depends on the r a d i a t i o n l o a d , a i r movement, o r g a n d i m e n s i o n s , s p e c i f i c h e a t , p i g m e n t a t i o n o f t h e t i s s u e and t h e r e f l e c t i v e c h a r a c t e r i s t i c s o f the s u r f a c e (Ansare and Loomis 1959, S a l i s b u r y and Spomer 1964, T r a n q u i l l i n i 1964). A i r movement i n the p r e s e n t t r i a l s was s u p p l i e d by f a n s o f t h e same s i z e and would t h e r e f o r e be e q u i v a l e n t among t r e a t m e n t s ; o r g a n t h i c k n e s s , p i g m e n t a t i o n , s p e c i f i c h e a t and r e f l e c t i v e c h a r a c t e r i s t i c s were assumed t o be e q u a l s i n c e f r u i t s o f t h e same v a r i e t y , p h y s i o l o g i c a l age, s i z e and h i s t o r y ( i . e . g r o w i n g c o n d i t i o n s ) were u s e d . D e s p i t e t h e u n i f o r m a i r t e m p e r a t u r e i n a l l t h e t r e a t m e n t s , f r u i t 139 -F i g u r e 24a. Near I n f r a r e d A b s o r p t i o n Spectra of F r e e z e - d r i e d Tomato F r u i t T i s s u e i n Chloroform (700-2500 nm). s o l v e n t a b s o r p t i o n spectrum a b s o r p t i o n spectrum o f u n t r e a t e d f r u i t t i s s u e at the mature-green stage of r i p e n e s s a b s o r p t i o n spectrum of u n t r e a t e d f r u i t t i s s u e at the f u l l r e d stage of r i p e n e s s a b s o r p t i o n spectrum of a f r u i t w i t h "advanced" type of i n j u r y 8 days a f t e r treatment W A V E L E N G T H (nm) 1000 130n 1600 1900 2200 2500 i '•* i — — J 1 • 1 r - i — ' t 1 '•" V — ^ 1 r " * * 1! i A Hi 1 ^ \ VA L——^  t 1 1 J !!] lj F i g u r e 24a. - 140 -F i g u r e 2 4b. I n f r a r e d A b s o r p t i o n S p e c t r a o f F r e e z e - d r i e d T i s s u e i n Carbon T e t r a c h l o r i d e (2.5-14 urn) ( i ) s o l v e n t a b s o r p t i o n s p e c t r u m ( i i ) a b s o r p t i o n s p e c t r u m o f u n t r e a t e d f r u i t t i s s u e a t t h e f u l l r e d stage o f r i p e n e s s ( i i i ) a b s o r p t i o n s p e c t r u m o f a f r u i t w i t h "advanced" t y p e o f i n j u r y 8 days a f t e r t r e a t m e n t - 141 " F i g u r e 24b. - 142 -t e m p e r a t u r e was h i g h e s t and r e a c h e d i t s peak f a s t e s t i n the t r e a t m e n t u s i n g u n f i l t e r e d r a d i a t i o n from a lamp s o u r c e LUR ( F i g . 8 ) , w h i c h was t h e same t r e a t m e n t t h a t p r o d u c e d the most s e v e r e i n j u r y . The s e v e r i t y o f i n j u r y seemed t o be r e l a t e d t o t h e f r u i t - a i r t e m p e r a t u r e d i f f e r e n t i a l . Among t h e t r e a t m e n t s , t h e h e a t t r e a t m e n t s HER and HWR had the l o w e s t f r u i t - a i r t e m p e r a t u r e d i f f e r e n t i a l . Reduced f r u i t - a i r t e m p e r a t u r e d i f f e r e n t i a l was a s s o c i a t e d w i t h a r e d u c t i o n o r t o t a l absence o f m e a s u r a b l e i n j u r y . T h i s was the f i r s t i n d i c a t i o n t h a t t e m p e r a t u r e was a c o n t r i b u t i n g f a c t o r t o the development o f i n j u r y . The t r i a l i n v o l v i n g h i g h t e m p e r a t u r e t r e a t m e n t s a l o n e ( T a b l e 9) c o n f i r m e d t h a t h i g h t e m p e r a t u r e s c a n p r o d u c e i n j u r y . The c o l o u r o f t h e f r u i t s s u b j e c t e d t o h i g h t e m p e r a t u r e t r e a t m e n t was somewhat g r e y i s h compared t o t h e w h i t e r c o l o u r o b t a i n e d whenever g r e e n f r u i t s were exposed t o u n f i l t e r e d r a d i a t i o n . However, t h e p r o g r e s s i o n o f t h e i n j u r y was s i m i l a r t o t h a t o b t a i n e d i n t h e u n f i l t e r e d r a d i a n t energy t r e a t m e n t . F u r t h e r m o r e , f r u i t a p p e a r a n c e a t t h e p o s t - r i p e n i n g s t a g e c o u l d n o t be~ d i f f e r e n t i a t e d from t h a t o f f r u i t exposed t o u n f i l t e r e d r a d i a t i o n w h i c h e x h i b i t e d t h e t y p i c a l r a d i a t i o n s c a l d i n j u r y syndrome. Both t y p e s o f i n j u r y were t h e r e f o r e c o n s i d e r e d t o be e s s e n t i a l l y s i m i l a r . The r e d u c e d e f f e c t i v e n e s s o f h e a t t r e a t m e n t s compared w i t h e i t h e r f u l l or n e a r i n f r a - r e d r a d i a t i o n t r e a t m e n t s , i n - 143 -p r o d u c i n g i n j u r y a t t h e same a i r t e m p e r a t u r e ( F i g . 7 , T a b l e 7) was p r o b a b l y due t o t h e d i f f e r e n t modes o f e n e r g y d e p o s i t i o n i n the f r u i t s by t h e h e a t and r a d i a t i o n s o u r c e s . The i n c a n d e s c e n t lamp a p p r o x i m a t e s a p o i n t s o u r c e w h i l e t h e h e a t i n g e l e m e n t i s a s u r f a c e e l e m e n t w i t h . a l a r g e a r e a . I f we assume t h a t b o t h e m i t comparable f l u x t o a c h i e v e t h e e q u a l a i r t e m p e r a t u r e s w h i c h were m a i n t a i n e d i n the t r e a t m e n t e n c l o s u r e s , t h e n the r a d i a n t f l u x i n t e n s i t y p e r u n i t a r e a i n d i r e c t i o n o f e m i s s i o n ( i . e . R a d i a n c e ) , i s : Le = dF/dw f o r t h e p o i n t s o u r c e , where dF i s t h e f l u x e m i t t e d from a p o i n t s o u r c e , and dw i s the s o l i d a n g l e i n t o w h i c h f l u x i s e m i t t e d . The R a d i a n c e f o r t h e h e a t i n g element i s r e d u c e d by a f a c t o r , dSCos y , w h i c h i s the p r o j e c t e d a r e a o f t h e s u r f a c e e l e m e n t ( i . e . Le = (dF/dw)/dScos y f o r a s u r f a c e e l e m e n t ( M o n t e i t h 1 9 7 3 ) ) . T h u s , a l t h o u g h the h e a t t r e a t m e n t u s i n g h e a t i n g e l e m e n t s o u r c e , was a p p l i e d v e r t i c a l l y ( i . e . s i m i l a r t o t h e mode o f a p p l i c a t i o n o f r a d i a t i o n from lamps) on f r u i t s s i t t i n g s t y l a r end up i n t r e a t m e n t c h a m b e r s , t h e amount o f l o n g wave i n f r a - r e d r a d i a t i o n i n t e r c e p t e d by t h e f r u i t was much r e d u c e d i n the h e a t t r e a t m e n t as e x p l a i n e d above. T h i s a l s o e x p l a i n s why t h e hot w a t e r - b a t h t r e a t m e n t was s i m i l a r l y n o t e f f e c t i v e . I t s r a d i a t i o n was d i f f u s e d and n o t u n i d i r e c t i o n a l . The h y p o t h e s i s t h a t t h e d i f f e r e n c e s i n t h e e f f e c t i v e -n e s s o f t h e v a r i o u s wavebands employed i n t h i s s t u d y was due t o u n e q u a l q u a n t a , c o u l d n o t be u p h e l d s i n c e t h e h e a t ( l o n g wave r a d i a t i o n ) t r e a t m e n t was n o t as e f f e c t i v e as t h e i n f r a -r e d waveband, i n i n d u c i n g i n j u r y a t comparable t e m p e r a t u r e s . - 144 -F u r t h e r m o r e , when i n j u r y was i n d u c e d by h e a t t r e a t m e n t a t t e m p e r a t u r e s 50°C, t h e c a l y x end ( d i s t a l t o r a d i a n t energy s o u r c e ) t h a t was more a f f e c t e d by c o n v e c t i v e h e a t , was a l s o i n j u r e d , t h o u g h , t o a l e s s e r degree when compared t o t h e s t y l a r e n d . From a l l the e v i d e n c e p r e s e n t e d i n t h i s s t u d y , i t i s h e r e b y c o n c l u d e d t h a t i n j u r y i s m a i n l y c a u s e d by h i g h f r u i t t e m p e r a t u r e s . The d i f f e r e n t e f f e c t i v e n e s s o f r a d i a n t energy s u c h as u n f i l t e r e d r a d i a t i o n and i n f r a - r e d r a d i a t i o n from l i g h t s o u r c e s compared w i t h h e a t t r e a t m e n t s i s r e l a t e d t o t h e mode o f r a d i a t i o n d e p o s i t i o n i n t h e f r u i t s as e x p l a i n e d p r e v i o u s l y . A b s o r p t i o n o f i n f r a - r e d r a d i a t i o n does n o t appear t o depend on a s p e c i a l c h r o m o p h o r i c system i n t h e f r u i t t i s s u e s . The tomato f r u i t i n t h e f r e s h s t a t e g e n e r a l l y has about 70-93% m o i s t u r e c o n t e n t and the i n f r a - r e d r a d i a t i o n i s m a i n l y a b s o r b e d by w a t e r i n t h e t i s s u e s and t r a n s f o r m e d i n t o h e a t . One major c o n s t r a i n t i n p h o t o b i o l o g i c a l e x p e r i m e n t s i s t h e d i f f i c u l t y o f p r o d u c i n g r a d i a n t energy o f h i g h i r r a d i a n c e v a l u e s i n t h e i n f r a - r e d w a v e l e n g t h s and t o a p p l y i t t o p l a n t m a t e r i a l s a t low t i s s u e t e m p e r a t u r e s . The medium f l o o d c o o l l u x 300 Watt i n c a n d e s c e n t S y l v a n i a lamp u s e d i n t h i s s t u d y i s c o a t e d w i t h a d i c h r o i c r e f l e c t o r t o d i s s i p a t e some o f i t s heat i n t o t h e s u r r o u n d i n g s . N e v e r t h e l e s s a l a r g e p e r c e n t a g e o f the h e a t p r o d u c e d accompanies t h e beam o f r a d i a n t e n e r g y t h e lamp e m i t s . I t would be i n t e r e s t i n g t o f i n d out i f i n j u r y can d e v e l o p i n f r u i t s e x p o s e d t o i n f r a - r e d r a d i a t i o n a t 20°C o r l e s s under wind c o n d i t i o n s s i m i l a r t o t h o s e o c c u r r i n g u n d e r f i e l d c o n d i t i o n s . - 145 -P o s s i b l e Mechanisms o f I n j u r y Development P h o t o o x i d a t i o n has been found t o be the cause o f some l e a f c h l o r o s i s ( K e t e l l a p e r 1969) and i n j u r y i n h e a t e d l e a v e s (Lomagin and A n t r o p o v a 1966) whenever l e a v e s were exposed t o " h i g h l i g h t i n t e n s i t i e s " . L e v i t t (1972) a l s o r e p o r t e d t h a t " h i g h l i g h t i n t e n s i t y , p a r t i c u l a r l y i f accompanied by h i g h i n f r a - r e d " , w o u l d p r o d u c e s u n s c a l d . S i n c e t h e o c c u r r e n c e o f s u n s c a l d - l i k e i n j u r i e s as r e p o r t e d i n t h i s s t u d y as w e l l as i n t h e l i t e r a t u r e was always h i g h e r under s o u r c e s t h a t a l s o e m i t l i g h t , t h e e x p e r i m e n t was done t o i n v e s t i g a t e t h e r o l e o f oxygen i n i n j u r y d e v e l o p m e n t . The r e s u l t s o f t h a t e x p e r i m e n t ( T a b l e 11) seem t o e x c l u d e p h o t o o x i d a t i o n from a r o l e i n the d e v e l o p m e n t o f i n j u r y i n tomato f r u i t s . I n j u r y o c c u r r e d f o l l o w i n g r a d i a t i o n t r e a t m e n t s i n an atmosphere d e v o i d o f oxygen (100% N 2 ) as w e l l as i n the p r e s e n c e o f oxygen (21% and 100% 0 2 ) . I t i s r e a l i s e d , however, t h a t the f r u i t t i s s u e s may have c o n t a i n e d t r a c e amounts o f 0 2 s i n c e t h e g r e e n f r u i t s may have g e n e r a t e d some 0 2 v i a p h o t o s y n t h e s i s . The q u a n t i t y o f 0 2 so p r o d u c e d , however, would be v e r y s m a l l and t h e f a c t t h a t t h e i n j u r y was a l s o p r o d u c e d under h i g h t e m p e r a t u r e t r e a t m e n t s i n t h e d a r k does n o t s u p p o r t t h e i n v o l v e m e n t o f p h o t o o x i d a t i o n as an e s s e n t i a l s t e p i n t h e development o f i n j u r y . In t h e absence o f 0 2 , as i n t h e h e a t t r e a t m e n t s a p p l i e d i n d a r k n e s s the c o l o u r o f the f r u i t s a t t h e i n j u r e d a r e a a f t e r t r e a t m e n t was g r e y i s h , b u t t h e i n j u r e d f r u i t s from t h e v a r i o u s oxygen t r e a t m e n t s were s i m i l a r f o l l o w i n g s t o r a g e and r i p e n i n g . - 146 " B e s i d e c h l o r o p h y l l d e g r a d a t i o n , o t h e r common v i s i b l e e f f e c t s o b s e r v e d d u r i n g the p r e s e n t s t u d i e s o f tomato i n j u r y a r e " f o a m i n g " and s k i n r u p t u r e e s p e c i a l l y i n f r u i t s t h a t have p a s s e d the t u r n i n g s t a g e o f r i p e n e s s ( F i g . 25 ) . Both o f t h e s e e f f e c t s a r e p r o b a b l y h e a t e f f e c t s . I n c r e a s i n g f r u i t t e m p e r a t u r e s would l e a d t o gaseous e x p a n s i o n w i t h i n the f r u i t . In a d d i t i o n , t h e r e m i g h t a l s o be c e l l s e p a r a t i o n due t o t h e r m a l e x p a n s i o n a c c o r d i n g t o t h e " s l o u g h i n g " t h e o r y o f R a t h s a c k (1935) (Hoff 1973). B o t h o f t h e s e p r o b a b l y c o n t r i b u t e d t o the " f o a m i n g " o b s e r v e d w i t h i n t h e i n j u r e d f r u i t s . S k i n r u p t u r e i s p r o b a b l y t h e r e s u l t o f r a d i a l and t a n g e n t i a l s h e a r s t r e s s e s g e n e r a t e d by t h e r m a l e x p a n s i o n o f f r u i t t i s s u e s and g a s e s . The r e s u l t s o f the p h o t o o x i d a t i o n and h i g h t e m p e r a t u r e e x p e r i m e n t s s u g g e s t t h a t t h e r e a r e p e r h a p s a t l e a s t two mechanisms c o n t r i b u t i n g t o t h e development o f s u n s c a l d - l i k e i n j u r i e s i n f r u i t s d i r e c t l y exposed t o r a d i a n t e n e r g y : One i n v o l v i n g p h o t o o x i d a t i o n r e q u i r i n g b o t h l i g h t and oxygen i n a d d i t i o n t o h e a t and r e s u l t i n g i n t h e c h a r a c t e r i s t i c b l e a c h i n g o b s e r v e d i n g r e e n f r u i t s ; and t h e o t h e r i n v o l v i n g h e a t a l o n e and r e s p o n s i b l e f o r t i s s u e breakdown i n c l u d i n g t h e r m a l d e g r a d a t i o n o f t h e c h l o r o p l a s t . T h e r e f o r e t h e v a r i o u s i n j u r i e s c l a s s i f i e d under t h e s u n s c a l d complex may n o t be q u i t e the same. They a r e e i t h e r p r o d u c t s o f d i f f e r e n t b i o c h e m i c a l pathways o r p e r h a p s g r a d a t i o n i n the syndrome p r o d u c e d by a major pathway. Hence t h e d i v e r s i t y o f names such as "gray w a l l " (Lorenz and K n o t t 1942). " s u n b u r n " ( R e t i g and Kedar 1967), " s o l a r y e l l o w i n g " ( L i p t o n 1970), u s e d by t h e v a r i o u s a u t h o r s . - 147 -Figure 25. Photographs of Tomato F r u i t s at the Red Stage of Ripeness Showing "foaming'1 and " p e r i c a r p " "rupture" R e s u l t i n g From Exposure to Intense Electromagnetic R a d i a t i o n . - 148 -Changes i n F o r c e - D e f o r m a t i o n C h a r a c t e r i s t i c s  E f f e c t s o f R i p e n e s s ( T a b l e 15) Changes i n f o r c e - d e f o r m a t i o n c h a r a c t e r i s t i c s o f tomato f r u i t s r e s u l t i n g from i n j u r y can be b e s t u n d e r s t o o d by c o n s i d e r i n g them i n r e l a t i o n t o t e x t u r a l changes known t o be a s s o c i a t e d w i t h f r u i t r i p e n i n g . Tomato f r u i t r i p e n i n g l e a d s t o a l o s s o f f r u i t f i r m n e s s (Gormley and K a p p e l 1976, H a l l 1964, H o l t 1970) r e d u c t i o n s i n s k i n and mesocarp s t r e n g t h s ( H o l t 1970) and i n c r e a s e i n d e f o r m a t i o n (Kader e t a i . 1978). In t h i s s t u d y , t h e s o f t e n i n g o f f r u i t s d u r i n g r i p e n i n g was a s s o c i a t e d w i t h i n c r e a s e d d e f o r m a t i o n and c o m p l i a n c e , w h i l e p e r i c a r p s t r e n g t h , mesocarp r e s i s t a n c e and f i r m n e s s d e c r e a s e d ( T a b l e 1 4 ) . Changes i n d e f o r m a t i o n were g r a d u a l d u r i n g t h e e a r l y r i p e n i n g p e r i o d , b u t i n t h e c a s e o f mesocarp r e s i s t a n c e , t h e r e was a r a p i d d e c r e a s e between r i p e n e s s s t a g e s 1 and 3. T h i s c o n f i r m s t h e r e s u l t s o f H o l t (1970) who was t h e f i r s t t o r e p o r t a r a p i d change i n t h e f i r m n e s s o f the mesocarp and t h e e n d o c a r p d u r i n g t h e e a r l y s t a g e s o f r i p e n i n g . However, c o n t r a r y t o H o l t ' s o b s e r v a t i o n o f a p r o g r e s s i v e d e c r e a s e i n e x o c a r p s t r e n g t h , a f a i r l y l a r g e d r o p i n p e r i c a r p s t r e n g t h was a l s o r e c o r d e d between s t a g e s 1 and 3 and t h e l a r g e s t d r o p i n d e f o r m a t i o n v a l u e s was measured between r i p e n e s s s t a g e s 3 and 5. These two f a c t o r s were r e s p o n s i b l e f o r t h e changes i n b o t h c o m p l i a n c e and f i r m n e s s v a l u e s s i n c e t h e y were r e s p e c t i v e l y d e r i v e d as t h e r a t i o and r e c i p r o c a l r a t i o o f d e f o r m a t i o n and p e r i c a r p f o r c e . - 1 4 9 -I t may be n o t e d t h a t q u a n t i t a t i v e l y t h e h i g h e s t f r u i t f i r m n e s s and p e r i c a r p s t r e n g t h v a l u e s were r e c o r d e d on u n i n j u r e d f r u i t s a t t h e t u r n i n g s t a g e o f r i p e n e s s . H o l t (1970) has p r o v i d e d s i m i l a r d a t a . F o l l o w i n g f r u i t - s e t i s a p e r i o d o f r a p i d c e l l d i v i s i o n , c e l l d i f f e r e n t i a t i o n and e n l a r g e m e n t , w i t h c o n c o m i t a n t i n c r e a s e s i n s t a r c h , c e l l u l o s e h e m i c e l l u l o s e s and p e c t i c sub stances u n t i l t h e f r u i t r e a c h e s i t s maximum s i z e a t m a t u r i t y . Beyond m a t u r i t y , the c o n c e n t r a t i o n s o f t h e s e c h e m i c a l c o n s t i t u e n t s d e c r e a s e . S i n c e f r u i t " f i r m n e s s " i s known t o i n c r e a s e up t o m a t u r i t y , beyond w h i c h i t s t a r t s to d e c l i n e , i t may be t h a t the " t u r n i n g " s t a g e i s t h e t r u e s t a g e o f p h y s i o l o g i c a l m a t u r i t y o f tomato f r u i t s . Toughness (the t o t a l energy a b s o r b e d by the f r u i t d u r i n g measurement) was r e l a t i v e l y c o n s t a n t i r r e s p e c t i v e o f t h e s t a g e o f r i p e n e s s . T h i s c h a r a c t e r i s t i c i s t h e r e f o r e c o n s i d e r e d i n a p p r o p r i a t e f o r use i n d e t e c t i n g changes i n the r i p e n e s s o f tomato f r u i t s . E f f e c t s o f S t o r a g e ( T a b l e 15) Changes i n f o r c e - d e f o r m a t i o n c h a r a c t e r i s t i c s f o l l o w i n g p o s t - t r e a t m e n t s t o r a g e showed t h e same p a t t e r n and were s i m i l a r i n magnitude t o t h e r i p e n e s s changes n o t e d above. R i p e n i n g p r o c e s s e s a r e known t o c o n t i n u e d u r i n g s t o r a g e when f r u i t s a r e s t o r e d a t optimum c o n d i t i o n s . The s t o r a g e c o n d i t i o n s employed - 150 -i n t h i s e x p e r i m e n t were t h o s e t h a t a r e known t o r e s u l t i n optimum r i p e n i n g . However, t h e r e s u l t s r e v e a l t h a t s t o r e d f r u i t s (stage 6 r i p e n e s s ) showed c o n s i s t e n t l y g r e a t e r t e x t u r a l i n d i c e s ( h i g h e r p e r i c a r p s t r e n g t h , mesocarp r e s i s t a n c e , f r u i t f i r m n e s s ; and l o w e r d e f o r m a t i o n and c o m p l i a n c e v a l u e s ) t h a n v i n e - r i p e f r u i t s a n a l y z e d a t t h e f i r m r i p e s t a g e (Ripeness s t a g e 5 ) . T h i s a p p a r e n t anomaly was due t o i n j u r y r a t h e r t h a n s t o r a g e p e r s e . S t o r a g e a v e r a g e s were computed o v e r t h e v a r i o u s i n j u r y l e v e l s . I n j u r y as w i l l be seen l a t e r i n t h i s d i s c u s s i o n i n c r e a s e d t h e t e n d e n c y o f f r u i t s t o become " f i r m e r " i n s t o r a g e . E f f e c t s o f F r u i t P o s i t i o n The p h y s i c a l measurements made a t d i f f e r e n t f r u i t o r i e n t a t i o n s p r o v i d e d d a t a on t h e c h a r a c t e r i s t i c s o f f r u i t " f i r m n e s s " i n t h e s t y l a r , e q u a t o r i a l and c a l y x p o s i t i o n s . I t s h o u l d be n o t e d , however, t h a t t h e r a d i a t i o n t r e a t m e n t s were a p p l i e d so t h a t t h e i n j u r y was i n i t i a t e d i n t h e s t y l a r p o r t i o n o f t h e f r u i t s and s p r e a d toward t h e c a l y x e n d . In t h e absence o f i n j u r y , t h e r e was a d e c l i n e i n p e r i c a r p s t r e n g t h , mesocarp r e s i s t a n c e , f i r m n e s s and t o u g h n e s s g o i n g from the s t y l a r end t o t h e c a l y x , and t h e r e was an i n c r e a s e i n c o m p l i a n c e . H o l t (1970) showed t h a t t h e weakest p a r t o f t h e tomato s k i n i s a t t h e " s h o u l d e r " , t h u s a c c o u n t i n g f o r t h e l o c a t i o n o f p r e - h a r v e s t s p l i t t i n g i n tomato f r u i t s . The " c a l y x p o s i t i o n " i n t h i s s t u d y - 151 -c o r r e s p o n d s t o H o l t ' s f r u i t " s h o u l d e r " . Toughness v a l u e s and p e r i c a r p s t r e n g t h were c o n s i s t e n t l y l o w e s t a t the c a l y x e n d . P h y s i o l o g i c a l l y , t h e tomato f r u i t " s h o u l d e r " i s the o l d e s t p a r t b e c a u s e i t i s i n t h a t a r e a where c e l l d i f f e r e n t i a t i o n and e n l a r g e m e n t f i r s t s t a r t e d . I t would appear t h a t the f r u i t s k i n may have undergone i t s maximum s t r e t c h i n g a t t h a t p o i n t . On t h e c o n t r a r y , t h e l o w e s t d e f o r m a t i o n v a l u e s were a l s o r e c o r d e d a t t h e c a l y x e n d . T h i s may have been due t o one o r b o t h o f two f a c t o r s : t h e ease o f s k i n p u n c t u r e due t o the weakness o f t h e s k i n (exocarp) a t t h e s h o u l d e r s as e x p l a i n e d above, o r t h e p r o x i m i t y o f t h e woody c a l y x w h i c h would a p p e a r t o r e i n f o r c e t i s s u e s a t t h e c a l y x end a g a i n s t d e f o r m a t i o n . E f f e c t s o f F r u i t I n j u r y ( T a b l e 15) The p a t t e r n o f v a r i a t i o n i n f o r c e - d e f o r m a t i o n c h a r a c t e r i s t i c s o v e r t h e s u r f a c e o f f r u i t s w i t h " i n c i p i e n t " i n j u r y was n o t much d i f f e r e n t from the u n i n j u r e d f r u i t s . T h i s was n o t s u r p r i s i n g s i n c e o n l y a s m a l l s t y l a r p o r t i o n o f t h e f r u i t was a f f e c t e d by " i n c i p i e n t " i n j u r y . T h u s , o n l y measurements a t t h e s t y l a r end c o u l d d e t e c t d i f f e r e n c e s due t o i n j u r y . As i n j u r y a d v a n c e d , t h e s i t u a t i o n became d i f f e r e n t . The l o w e s t f i r m n e s s o r h i g h e s t c o m p l i a n c e v a l u e s were r e c o r d e d a t t h e ' e q u a t o r i a l " r e g i o n w h i c h i n t h e c a s e o f the advanced i n j u r y c o i n c i d e d w i t h t h e i n t e r f a c e between t h e i n j u r e d and -152 -u n i n j u r e d p o r t i o n s o f t h e f r u i t . I n j u r y i t s e l f l o w e r e d f i r m n e s s v a l u e s . T h i s e x p l a i n s why t h e l o w e s t f i r m n e s s v a l u e s i n f r u i t s w i t h " i n c i p i e n t " i n j u r y o c c u r r e d a t the s t y l a r e n d . In u n i n j u r e d f r u i t s u n d e r g o i n g normal r i p e n i n g , i n c r e a s e d p e r i c a r p s t r e n g t h was always accompanied by r e d u c e d d e f o r m a t i o n and v i c e v e r s a . T h i s was n o t t h e c a s e w i t h f r u i t s h a v i n g "advanced" t y p e o f i n j u r y . H i g h p e r i c a r p s t r e n g t h was accompanied by l a r g e d e f o r m a t i o n and hence low f i r m n e s s v a l u e s . T h i s was a s t o r a g e e f f e c t m e d i a t e d t h r o u g h r i p e n i n g . D u r i n g s t o r a g e , u n i n j u r e d p o r t i o n s o f the f r u i t r i p e n e d and hence " s o f t e n e d " n o r m a l l y w h i l e the i n j u r e d a r e a r e m a i n e d p r a c t i c a l l y unchanged i n b o t h c o l o u r and t e x t u r e . S i n c e p u n c t u r e t e s t s were done by a p p l y i n g f o r c e on f r u i t s a l i g n e d s t y l a r end up on t h e i r v e r t i c a l a x i s , i t f o l l o w s t h a t most o f t h e d e f o r m a t i o n was due t o t h e " c u s h i o n i n g e f f e c t " p r o d u c e d by t h e s o f t e n e d u n i n j u r e d c a l y x h a l f o f t h e f r u i t . However, t h e method i s p r o b a b l y a p p r o p r i a t e s i n c e i t t e n d s t o s i m u l a t e t h e way consumers e v a l u a t e f r u i t f i r m n e s s a t the r e t a i l l e v e l . No l a r g e changes were found c o n c e r n i n g the e f f e c t o f i n j u r y on f o r c e - d e f o r m a t i o n c h a r a c t e r i s t i c s a t v a r i o u s s t a g e s o f r i p e n e s s . I n j u r y f u r t h e r enhanced changes i n f o r c e -d e f o r m a t i o n c h a r a c t e r i s t i c s a s s o c i a t e d w i t h s o f t e n i n g , the o n l y e x c e p t i o n s b e i n g p e r i c a r p s t r e n g t h and t o u g h n e s s . The enhancement o f p e r i c a r p s t r e n g t h by i n j u r y d i s a p p e a r e d a t l a t e r s t a g e s o f r i p e n e s s . Toughness was i n c r e a s e d by i n j u r y - 153 -a t the e a r l y r i p e n e s s s t a g e s . F r u i t d e f o r m a t i o n and c o m p l i a n c e i n c r e a s e d s t e a d i l y w h i l e f r u i t f i r m n e s s d e c r e a s e d w i t h r i p e n e s s . I t w i l l be wrong t o c o n c l u d e , however, t h a t t h e e f f e c t o f i n j u r y was t o h a s t e n r i p e n i n g p r o c e s s e s . O b v i o u s l y , as w i l l be seen i n t h e r e s u l t s from o t h e r a s p e c t s o f t h i s s t u d y , no v i s i b l e r i p e n e s s changes were found i n t h e i n j u r e d p o r t i o n s o f t h e f r u i t s . T h i s p a t t e r n o f changes i n f o r c e - d e f o r m a t i o n c h a r a c t e r i s t i c s r e s u l t i n g from i n j u r y was t h e r e f o r e c o i n c i d e n t a l . E f f e c t s o f S t o r a g e on t h e F o r c e - D e f o r m a t i o n  C h a r a c t e r i s t i c s o f I n j u r e d F r u i t s ( F i g . 11) Changes i n f o r c e - d e f o r m a t i o n c h a r a c t e r i s t i c s due t o i n j u r y were much more e v i d e n t f o l l o w i n g s t o r a g e . The r e d u c e d p e r i c a r p s t r e n g t h and mesocarp r e s i s t a n c e a s s o c i a t e d w i t h s t o r a g e o r r i p e n e s s d i s a p p e a r e d a t h i g h e r i n j u r y l e v e l s . But f r u i t d e f o r m a t i o n and hence t o u g h n e s s was i n c r e a s e d by i n j u r y f o l l o w i n g s t o r a g e s i n c e the l a t t e r was c a l c u l a t e d as h a l f the p r o d u c t o f d e f o r m a t i o n and p e r i c a r p f o r c e . The i n c r e a s e d p o s t - s t o r a g e p e r i c a r p s t r e n g t h and mesocarp r e s i s t a n c e o f i n j u r e d f r u i t s compared w i t h u n i n j u r e d f r u i t s was c l e a r l y due t o t h e i n a b i l i t y o f t h e i n j u r e d s t y l a r p o r t i o n t o r i p e n and hence " s o f t e n " i n s t o r a g e . The i n c r e a s e d f r u i t d e f o r m a t i o n was a l s o due t o t h e g e n e r a l " c u s h i o n i n g " e f f e c t o f t h e c a l y x h a l f o f t h e f r u i t as e x p l a i n e d e a r l i e r . - 154 -E f f e c t s o f R i p e n e s s , I n j u r y and S t o r a g e on P r o t o p e c t i n The r o l e o f p e c t i c s u b s t a n c e s i n r e l a t i o n t o the t e x t u r a l c h a r a c t e r i s t i c s o f f r u i t s and v e g e t a b l e s i s w e l l documented ( K e r t e s z 1951; P i l n i k and V o r a g e n 1970). P e c t i c s u b s t a n c e s a r e known t o c o n t r i b u t e t o t h e m e c h a n i c a l s t r e n g t h o f t h e c e l l w a l l s and a r e l a r g e l y r e s p o n s i b l e f o r the a d h e s i o n between c e l l s (Appleman and C o n r a d 1927; Van B u r e n 1 9 7 9 ; K e r t e s z 1951). R i p e n i n g i n t h e tomato i s accompanied by s o f t e n i n g w h i c h i n t u r n i s accompanied by t h e h y d r o l y s i s o f i n s o l u b l e p r o t o p e c t i n by p o l y g a l a c t u r o n a s e , and a c o n c o m i t a n t i n c r e a s e i n s o l u b l e p e c t i n . T h i s v i e w i s i n agreement w i t h the g e n e r a l d e c l i n e i n p r o t o p e c t i n c o n t e n t w h i c h was found w i t h i n c r e a s i n g r i p e n e s s and s t o r a g e i n the absence o f i n j u r y , i n t h i s s t u d y . P r o t o p e c t i n c o n t e n t was i n c r e a s e d by i n j u r y and t h i s change, as w i t h t h e p h y s i c a l c h a r a c t e r i s t i c s j u s t d i s c u s s e d , was more e v i d e n t f o l l o w i n g s t o r a g e ( F i g . 1 5 a ) . I n j u r y i t s e l f i n t h e absence o f s t o r a g e , d i d n o t p r o d u c e any s i g n i f i c a n t change i n f r u i t p r o t o p e c t i n c o n t e n t . In canned t o m a t o e s , " f i r m n e s s " has been i n c r e a s e d by h o l d i n g f r u i t s a t 70-100°C f o r s h o r t p e r i o d s (Luh and Daoud 1971, Hsu e t a_l. 1965, S h e r k a t and Luh 1976). B a r t o l o m e and H o f f (1972) a l s o r e p o r t e d t h a t h e a t i n g p o t a t o t o 50-70°C had a " f i r m i n g e f f e c t " on the cooked t i s s u e s . - 155 ~ T h e r e seem t o be two main ways by w h i c h i n c r e a s e d f i r m n e s s may be a c c o m p l i s h e d as a r e s u l t o f e x p o s u r e t o h i g h t e m p e r a t u r e s . The enzymes p r o t o p e c t i n a s e and p o l y g a l a c t u r o n a s e , w h i c h a r e r e s p o n s i b l e . f o r t h e b r e a k i n g down o f i n s o l u b l e p e c t i c s u b s t a n c e s t o s o l u b l e f o r m s , may be i n a c t i v a t e d . A l t e r n a t i v e l y , i n c r e a s e d f i r m n e s s c o u l d be a c c o m p l i s h e d by a c h a i n o f r e a c t i o n s as p r o p o s e d by H o f f (1973). A c c o r d i n g t o H o f f , i n j u r y o f t h e plasmalemma c a u s e s c a t i o n s t o d i f f u s e i n t o t h e c e l l w a l l . I n c r e a s e d c a t i o n c o n c e n t r a t i o n m i g h t cause t h e r e l e a s e and i n a c t i v a t i o n p e c t i n - m e t h y l - e s t e r a s e w h i c h p r o c e e d s t o h y d r o l y s e t h e m e t h y l e s t e r g r o u p s o f p e c t i n . M i g r a t i o n o f d i v a l e n t c a t i o n s t o w a l l s i t e s l e a d s t o c r o s s l i n k i n g o f a d j a c e n t c a r b o x y l g r o u p s and a l s o p o l y u r o n i d e c h a i n s . I t i s known t h a t t h e tomato f r u i t s c o n t a i n p o l y g a l a c t u r o n a s e (Hobson 19 62, McCready e t a l . 1955, Reymond and P h a f f 1965). The r e s u l t s p r e s e n t e d h e r e s u g g e s t t h a t t h e i n a c t i v a t i o n o r t h e r m a l d e n a t u r a t i o n o f enzymes i s t h e more p l a u s i b l e e x p l a n a t i o n . The p r o t o p e c t i n c o n t e n t o f u n i n j u r e d f r u i t s d e c r e a s e d f o l l o w i n g s t o r a g e and r i p e n i n g . However, i n t h e p r e s e n c e o f i n j u r y , s t o r a g e a t optimum r i p e n i n g c o n d i t i o n s d i d n o t p r o d u c e a s i g n i f i c a n t change i n t h e p r o t o p e c t i n c o n t e n t . T h u s , the e x p o s u r e o f tomato f r u i t s t o r a d i a n t energy o f s u f f i c i e n t magnitude t o p r o d u c e i n j u r y seems t o l e a d t o t h e l o s s o f the mechanism o f p e c t i c s o l u b i l i z a t i o n a s s o c i a t e d w i t h n o r m a l r i p e n i n g . - 1 5 6 ~ P e c t i c s u b s t a n c e s a r e by no means t h e o n l y c e l l w a l l component u n d e r g o i n g changes d u r i n g r i p e n i n g . The r e s u l t s o f some s t u d i e s ( B e s f o r d and Hobson 1972, Knee 1974) i n d i c a t e d t h a t c e l l w a l l changes o t h e r t h a n p o l y g a l a c t u r o n a s e c a t a l y z e d p e c t i c s o l u b i l i z a t i o n m i g h t be i n v o l v e d i n r i p e n i n g . However, a r e c e n t i n v e s t i g a t i o n on t h e i n v o l v e m e n t o f c e l l w a l l p o l y s a c c h a r i d e s i n tomato f r u i t r i p e n i n g (Gross and W a l l n e r 1979) has shown t h a t t h e d i r e c t e f f e c t o f c e l l w a l l n e u t r a l s u g a r s i s m i n o r . The d e c l i n e i n g a l a c t o s e and a r a b i n o s e d u r i n g r i p e n i n g was f o u n d t o be r i p e n i n g - r e l a t e d b u t s e p a r a t e from and i n d e p e n d e n t o f p o l y u r o n i d e s o l u b i l i z a t i o n . C e l l u l a s e a c t i v i t y has a l s o been found t o d o u b l e d u r i n g tomato r i p e n i n g , b u t Hubson (1968) f o u n d no c o r r e l a t i o n between c e l l u l a s e a c t i v i t y and f i r m n e s s . A t p r e s e n t , i t a p p e a r s t h a t t h e o n l y c e l l w a l l change t h a t i s c l e a r l y r e l a t e d t o tomato f r u i t s o f t e n i n g i s t h e h y d r o l y s i s o f t h e # - 1 , 4 - g a l a c t u r o n o s y l l i n k a g e s by p o l y g a l a c t u r o n a s e . W i t h t h i s i n m i n d , c o r r e l a t i o n a n a l y s e s were done f o r p r o t o p e c t i n and f o r c e - d e f o r m a t i o n c h a r a c t e r i s t i c s . The r e s u l t s o f t h e c o r r e l a t i o n s t u d i e s by s t r a t a f o r i n j u r y ( T a b l e 18) r e v e a l e d t h a t i n t h e absence o f i n j u r y , p r o t o p e c t i n c o n t e n t was w e l l c o r r e l a t e d w i t h f o u r f o r c e - d e f o r m a t i o n c h a r a c t e r i s t i c s : p e r i c a r p s t r e n g t h , mesocarp r e s i s t a n c e c o m p l i a n c e and f i r m n e s s (R ^ . 7 8 ) . However, i n t h e p r e s e n c e o f i n j u r y , c o m p l i a n c e and f i r m n e s s were t h e f o r c e - d e f o r m a t i o n c h a r a c t e r i s t i c s most h i g h l y c o r r e l a t e d w i t h p r o t o p e c t i n . In the work by Foda (1957), T a b l e 18. C o r r e l a t i o n C o e f f i c i e n t s R e l a t i n g P r o t o p e c t i n C o n c e n t r a t i o n w i t h F o r c e - D e f o r m a t i o n C h a r a c t e r i s t i c s . I n j u r y D e f o r m a t i o n P e r i c a r p Mesocarp C o m p l i a n c e F i r m n e s s Toughness 0 - . 6 1 * .79* . 8 3 * - . 8 8 * .78* . 5 3 * 1 - . 7 8 * .57* . 5 3 * - . 8 1 * . 8 2 * - . 1 9 ns s 3 - . 2 8 ns . 8 1 * .54* - . 7 3 * .73* - . 3 3 ns L h-1 —I * S i g n i f i c a n t a t P = 0.01 ns N o t s i g n i f i c a n t a t P = 0.05 -158 -i n s t r u m e n t a l measurements o f tomato i n n e r p e r i c a r p t i s s u e f i r m n e s s were found t o c o r r e l a t e w i t h p r o t o p e c t i n c o n t e n t to the e x t e n t o f R > . 9 3 . O t h e r w o r k e r s (Deshpande e t a l . 1965,-Sayed e t al_. 1966) found s i g n i f i c a n t b u t lower c o r r e l a t i o n s (R ^ .71) between f i r m n e s s o f canned o r whole tomatoes and t o t a l p e c t i c s u b s t a n c e s . C r o s s - c o m p a r i s o n s between the p r e s e n t r e s u l t s and t h o s e r e p o r t e d e l s e w h e r e a r e d i f f i c u l t t o make s i n c e t h e methods o f f i r m n e s s d e t e r m i n a t i o n were d i f f e r e n t . However, i t i s r e a l i s e d t h a t p e c t i c s u b s t a n c e s a r e n o t t h e o n l y c h e m i c a l c o n s t i t u e n t s c o n t r i b u t i n g t o f i r m n e s s . N e i t h e r a r e c h e m i c a l c o n s t i t u e n t s t h e m s e l v e s the o n l y f a c t o r s a f f e c t i n g f r u i t f i r m n e s s . As K o s k i t a l o (1970) p o i n t e d o u t , c h e m i c a l a n a l y s i s does n o t a c c o u n t f o r p e r i c a r p t h i c k n e s s o r c a r p e l number, s i z e and arrangement, a l l o f w h i c h a l s o c o n t r i b u t e t o tomato f r u i t " f i r m n e s s " . I t i s i n t h i s r e s p e c t t h a t p h y s i c a l measurements a r e p r o b a b l y b e t t e r t h a n c h e m i c a l a n a l y s i s as i n d i c a t o r s o r f r u i t f i r m n e s s . The r e s u l t s o f a backward s t e p w i s e r e g r e s s i o n a n a l y s i s , o f p r o t o p e c t i n w i t h f o r c e - d e f o r m a t i o n c h a r a c t e r i s t i c s , p e r f o r m e d u s i n g t h e UBC TRP computer program,showed t h a t c o m p l i a n c e i s t h e b e s t p r e d i c t o r o f p r o t o p e c t i n i n d e t e c t i n g v a r i a b i l i t y due t o i n j u r y a t v a r i o u s s t a g e s o f r i p e n e s s and s t o r a g e i n 2 -v tomato f r u i t s (R = 90.4%; Sy = 1 . 9 7 ) . A l l o t h e r f o r c e -d e f o r m a t i o n c h a r a c t e r i s t i c s e x c e p t t o u g h n e s s were h i g h l y c o r r e l a t e d w i t h c o m p l i a n c e a t a l l l e v e l s o f i n j u r y (Table 19) . I t i s t h e r e f o r e c o n c l u d e d t h a t c o m p l i a n c e i s a b e t t e r c h a r a c t e r i s t i c t h a n f i r m n e s s i n d e t e c t i n g changes i n t e x t u r a l T a b l e 19. C o r r e l a t i o n C o e f f i c i e n t s R e l a t i n g c o m p l i a n c e w i t h Other F o r c e - D e f o r m a t i o n C h a r a c t e r i s t i c s . i n j u r y D e f o r m a t i o n s t r e n g t h R e s i s t a n c e F i r m n e s s Toughness 0 .72* - . 9 1 * - . 8 4 * - . 9 2 * - . 5 9 * 1 .74* - . 8 6 * - . 8 3 * - . 9 5 * - . 1 3 ns M 3 .77* - . 7 2 * - . 5 8 * - . 9 1 * - . 0 7 ns 1 * S i g n i f i c a n t a t P = 0.01 ns Not s i g n i f i c a n t a t P = 0.05 - 150 -i n d i c e s , o f tomato f r u i t s , r e s u l t i n g from e i t h e r r i p e n i n g o r i n j u r i e s due t o e x p o s u r e t o r a d i a n t e n e r g y . E f f e c t s o f R i p e n e s s , S t o r a g e and I n j u r y on A s c o r b i c A c i d C o n t e n t R e p o r t s i n t h e l i t e r a t u r e about t h e p a t t e r n o f change i n a s c o r b i c a c i d d u r i n g tomato r i p e n i n g have been i n c o n s i s t e n t . Clow and M a r l a t t (1930) o b s e r v e d t h a t f r u i t s h a r v e s t e d a t the m a t u r e - g r e e n and r i p e s t a g e s c o n t a i n e d t h e same q u a n t i t y o f a s c o r b i c a c i d . On t h e c o n t r a r y , o t h e r w o r k e r s ( S c o t t and Kramer 1949, P a n t o s and M a r k a k i s 1973) found d i f f e r e n t l e v e l s o f a s c o r b i c a c i d i n r i p e f r u i t s d e p e n d i n g on t h e i r r i p e n e s s b e f o r e h a r v e s t . R e c e n t l y , B i s o g n i and h i s c o - w o r k e r s (1976) found t h a t f i e l d - r i p e n e d f r u i t s had g r e a t e r a s c o r b i c a c i d c o n t e n t s t h a n d i d r o o m - r i p e n e d f r u i t s . V a r i a t i o n s i n the a s c o r b i c a c i d c o n t e n t o c c u r r e d w i t h d i f f e r e n t t i m e s o f h a r v e s t . I t i s l i k e l y t h a t t h e i n c o n s i s t e n c i e s among v a r i o u s r e p o r t s on a s c o r b i c a c i d c o n t e n t i n r i p e n i n g tomato f r u i t s a r e m a i n l y due t o d i f f e r e n t m e t h o d o l o g i e s and s a m p l i n g p r o c e d u r e s . In t h e p r e s e n t s t u d y , a s c o r b i c a c i d was found t o i n c r e a s e w i t h a d v a n c i n g r i p e n e s s ( F i g . 1 4 b ) , b u t i t was d e c r e a s e d s h a r p l y as a r e s u l t o f i n j u r y ( F i g . 15b). The s l i g h t i n c r e a s e i n a s c o r b i c a c i d c o n t e n t when f r u i t s were h e l d i n s t o r a g e was p r o b a b l y due t o r i p e n i n g . However, such an i n c r e a s e was n o t s u f f i c i e n t t o o f f s e t t h e d r a s t i c r e d u c t i o n i n a s c o r b i c a c i d c o n t e n t b r o u g h t a b o u t by i n j u r y . These r e s u l t s a r e i n agreement w i t h t h o s e o f F r y e r e t al_. (1954) . But t h e y a r e - - 161 -c o n t r a r y t o t h e r e p o r t s o f lower a s c o r b i c a c i d c o n t e n t i n unshaded whole f r u i t s o r f r u i t p a r t s , compared w i t h shaded ones i n t h e f i e l d , as found by some w o r k e r s (Crane and Z i l v a 1949, M c C o l l u m 1946). The l o w e r a s c o r b i c a c i d c o n t e n t r e s u l t i n g from i n j u r y was p r o b a b l y due t o o x i d a t i o n . The main pathway o f a s c o r b i c a c i d m e t a b o l i s m i s by o x i d a t i o n t o d e h y d r o a s c o r b i c a c i d w h i c h can i n t u r n be o x i d i z e d t o f u r t h e r d e g r a d a t i o n p r o d u c t s t h a t p o s s e s s no v i t a m i n C a c t i v i t y . The r a t e o f o x i d a t i o n i n c r e a s e s w i t h b o t h d u r a t i o n and l e v e l o f temperature. , b u t i t i s a l s o dependent on t h e a v a i l a b i l i t y o f oxygen ( S h e r k a t and Luh 197 6 ) . In t h i s s t u d y , a s c o r b i c a c i d c o n t e n t was d e t e r m i n e d u s i n g f r u i t s from t r e a t m e n t s w h i c h d i d n o t e x c l u d e o x y g e n . However, i t w i l l be r e c a l l e d t h a t i n t h e e a r l i e r p a r t o f t h i s s t u d y , i t was shown t h a t p h o t o o x i d a t i o n i s n o t a p r e r e q u i s i t e f o r i n j u r y d e v e l o p m e n t . T h u s , i n j u r y development i s p r o b a b l y n o t dependent on o x i d a t i v e changes i n a s c o r b i c a c i d a l t h o u g h t h e l o s s o f a s c o r b i c a c i d i s a s s o c i a t e d w i t h i n j u r y . E f f e c t s o f R i p e n e s s , S t o r a g e and I n j u r y oh Tomato F r u i t pH  The pH o f tomato f r u i t s i n c r e a s e s w i t h l a t e r h a r v e s t s (Hanna 1961, Yamaguchi e t a l . 1960) and a l s o w i t h i n c r e a s i n g t e m p e r a t u r e s d u r i n g the g r o w i n g season ( K o s k i t a l o 1970). In - 162 -t h e p r e s e n t s t u d y , f r u i t pH i n c r e a s e d w i t h i n c r e a s i n g v i n e r i p e n e s s , b u t s u c h i n c r e a s e s were n o t s t a t i s t i c a l l y s i g n i f i c a n t . S t o r a g e , however s i g n i f i c a n t l y i n c r e a s e d pH. T h i s i s c o n t r a r y t o t h e f i n d i n g s o f C r a f t and H e i n z e (1954) who r e p o r t e d t h a t s t o r a g e d u r a t i o n had no e f f e c t on pH. W i n s o r e t a l . (1962) had shown t h a t t h e a c i d i t y i n tomato f r u i t s i n c r e a s e s i n i t i a l l y t o a maximum c o i n c i d i n g a p p r o x i m a t e l y w i t h t h e f i r s t a p p e a r a n c e o f p i n k c o l o u r a t t h e t u r n i n g s t a g e . The i n c r e a s e i n pH due t o s t o r a g e c o u l d have r e s u l t e d from t h e o x i d a t i o n o f a c i d s as r e s p i r a t o r y s u b s t r a t e s d u r i n g r i p e n i n g . One c o u l d s p e c u l a t e t h a t v i n e r i p e f r u i t s were p a r t l y r e p l e n i s h e d i n t h e i r a c i d i t y from t h e p a r e n t p l a n t o r t h a t o t h e r r e s p i r a t o r y s u b s t r a t e s s u c h as s i m p l e s u g a r s were more i m p o r t a n t f o r t h e i r o x i d a t i v e p r o c e s s e s . I n j u r y a l s o i n c r e a s e d f r u i t p H . T h i s c o u l d be due t o t h e m e t a b o l i s m o f a c i d s a t t h e e l e v a t e d f r u i t t e m p e r a t u r e s d e v e l o p e d d u r i n g e x p o s u r e t o r a d i a n t e n e r g y . Such an e f f e c t would be c o n s i s t e n t w i t h t h e gas exchange changes r e v i e w e d i n t h e next s e c t i o n o f t h i s d i s c u s s i o n . H i g h b r e a k t e m p e r a t u r e s have been shown t o r e s u l t i n lower a c i d i t y o f tomato p a s t e (Luh and Daoud 1971). Such lower a c i d i t y o f tomato p a s t e d u r i n g p r o c e s s i n g was a t t r i b u t e d t o r a p i d i n a c t i v a t i o n o f p e c t i c enzymes (Luh and Daoud 1971) and l o s s o f v o l a t i l e a c i d s and C 0 0 a t h i g h t e m p e r a t u r e s ( S h e r k a t and Luh 1976). - 163 -The r o l e o f pH changes i n t h e development o f i n j u r y c a n n o t be d e t e r m i n e d on t h e b a s i s o f t h e r e s u l t s p r e s e n t e d h e r e . But t h e e f f e c t s o f low a c i d i t y on f r u i t q u a l i t y c a n n o t be o v e r l o o k e d . Low a c i d i t y i s an u n d e s i r a b l e q u a l i t y a t t r i b u t e f o r tomato p r o c e s s i n g . H i g h a c i d i t y i s r e q u i r e d f o r good c o l o u r , f l a v o u r , t e x t u r e and a s c o r b i c a c i d r e t e n t i o n (Gould 1957, Lambeth e t a l . 1966, L e o n a r d e t al_. 19 - 164 -Gas Exchange ( F i g s . 19, 20, 21 and 22) The enhancement o f CC>2 p r o d u c t i o n by t r e a t m e n t s t h a t p r o d u c e d " i n d u c t i o n " t y p e o f i n j u r y and t h e a c c e l e r a t i o n o f t h e c l i m a c t e r i c peak i n b o t h the " i n d u c t i o n " and " i n c i p i e n t " t y p e s o f i n j u r y might be due t o a s t i m u l a t i o n o f r i p e n i n g and hence t h e c l i m a c t e r i c r i s e by e l e c t r o m a g n e t i c r a d i a t i o n . V i s i b l e r a d i a t i o n t r e a t m e n t s have been shown t o i n c r e a s e the r a t e o f c o l o u r development (Boe and Salunkhe 1967; N e t t l e s e t a l . 1955; S h e w f e l t 1970) as w e l l as t o a c c e l e r a t e t h e o c c u r r e n c e o f t h e c l i m a c t e r i c peak d u r i n g r i p e n i n g (Jen and Watada 1977). B o t h p r o c e s s e s have now been c o n f i r m e d t o be p h y t o c h r o m e - m e d i a t e d ( K h u d a i r i and A b o l e d a 1971; J e n e t a l . 1977; J e n and Watada 1977; Thomas and J e n 1975). H a l l (1964) found t h a t p o s t - h a r v e s t e x p o s u r e s o f tomato f r u i t s t o an a i r t e m p e r a t u r e o f 32°C f o r s h o r t p e r i o d s i n c r e a s e d t h e i r c o l o u r d e v e l o p m e n t . T h i s s u g g e s t s t h a t t h e r e s u l t a n t r i s e i n f r u i t t e m p e r a t u r e d u r i n g e x p o s u r e t o r a d i a n t e n e r g y as i n t h i s s t u d y , i n c r e a s e d m e t a b o l i c r a t e s and t r i g g e r e d " r i p e n i n g " r e -a c t i o n s . I t would a p p e a r , t h e r e f o r e , t h a t t h e r e d u c e d p o s t -t r e a t m e n t r a t e o f r e s p i r a t i o n i n f r u i t s w i t h t h e advanced i n j u r y , may have been due t o t h e e x h a u s t i o n o f r e s p i r a t o r y s u b s t r a t e s as w e l l as t o the i n a c t i v a t i o n a n d / o r d e n a t u r a t i o n o f r e s p i r a t o r y enzymes i n t h a t p o r t i o n o f t h e f r u i t w h i c h was s u b j e c t e d t o p r o l o n g e d e x p o s u r e t o r a d i a n t e n e r g y . T h i s r a t i o n a l e , however, does n o t e x p l a i n t h e p a t t e r n o f f r u i t e t h y l e n e p r o d u c t i o n o b s e r v e d i n t h i s s t u d y . - 165 -I t i s known t h a t e t h y l e n e p r o d u c t i o n by most f r u i t s comes n e a r t o c e s s a t i o n a t t e m p e r a t u r e s o v e r 35°C (Abeles 1973, Burg 1962, Eaks 1978). T e m p e r a t u r e s o f 40°C o r h i g h e r have been found t o g r e a t l y s u p p r e s s o r s t o p e t h y l e n e p r o d u c t i o n i n t h e r i p e n i n g p e a r (Hansen 1942, M a x i e e t a_l. 1974). T h i s i s c o n t r a r y t o t h e f i n d i n g s o f t h e p r e s e n t s t u d y . E t h y l e n e p r o d u c t i o n was s t i m u l a t e d e s p e c i a l l y a t t h e p o s t -c l i m a c t e r i c s t a g e i n f r u i t s t h a t were exposed t o e l e v a t e d a i r t e m p e r a t u r e s . I t s h o u l d be p o i n t e d o u t , however, t h a t the r e p o r t s o f h i g h t e m p e r a t u r e - i n d u c e d e t h y l e n e p r o d u c t i o n , were from s t u d i e s on f r u i t s k e p t c o n t i n u o u s l y a t h i g h t e m p e r a t u r e s t h r o u g h o u t s t o r a g e . R e c e n t l y , Eaks (1978) has shown t h a t avocado f r u i t s h e l d f o r one o r two days a t 40°C and t h e n t r a n s f e r r e d t o 20°C resumed n o r m a l r i p e n i n g f u n c t i o n s s u c h as the c l i m a c t e r i c r i s e i n r e s p i r a t i o n , i n c r e a s e d e t h y l e n e ' p r o d u c t i o n and s o f t e n i n g . N o r m a l l y , the r e s p i r a t o r y c l i m a c t e r i c i s a s s o c i a t e d w i t h a c o n c o m i t a n t r i s e i n e t h y l e n e p r o d u c t i o n . In t h i s s t u d y , i t was found t h a t t h e r e l a t i o n s h i p between t h e r a t e o f r e s p i r a t i o n and e t h y l e n e p r o d u c t i o n i n the i n j u r e d f r u i t s was d i f f e r e n t from t h a t o f t h e u n i n j u r e d c o n t r o l s ( F i g . 2 1 ) . F o r example, advanced i n j u r y s u p p r e s s e d p o s t - t r e a t m e n t r a t e o f r e s p i r a t i o n but s t i m u l a t e d t h e r a t e o f e t h y l e n e p r o d u c t i o n when compared w i t h t h e c o n t r o l . T h i s s u g g e s t s a s h i f t i n m e t a b o l i s m . The f i n d i n g i s s i m i l a r t o t h a t o f Eaks (1978) - 166 " who found t h a t t h e r e s p i r a t o r y c l i m a c t e r i c and e t h y l e n e p r o d u c t i o n were i n d e p e n d e n t a t 35°C i n the avocado. In h i s s t u d y , avocado f r u i t s h e l d c o n t i n u o u s l y a t 35°C r i p e n e d and e x h i b i t e d t h e c h a r a c t e r i s t i c r e s p i r a t o r y c l i m a c t e r i c . However, c o n t r a r y t o t h e p r e s e n t f i n d i n g s , t h e avocado f r u i t s p r o d u c e d o n l y a t r a c e amount o f e t h y l e n e . E t h y l e n e p r o d u c t i o n c a n i n c r e a s e as a r e s u l t o f m e c h a n i c a l i n j u r y , d i s e a s e ( W i l l i a m s o n 1950) and o t h e r s t r e s s c o n d i t i o n s such as e x p o s u r e t o i o n i z i n g r a d i a t i o n s (Young 1965) s u l f u r d i o x i d e ( B r e s s a n e t a l . 1978, B r e s s a n e t a l . 1979, P e i s e r and Yang 1979) and ozone ( C r a k e r 1971). The amount o f e t h y l e n e p r o d u c e d i n c r e a s e s as the p r o p o r t i o n o f t h e t i s s u e i n j u r e d i n c r e a s e s ( E l s t n e r and Konze 1976, B r e s s a n e t a l . 1979) , but s t r e s s e s s u f f i c i e n t t o k i l l t h e c e l l s a l s o s t o p e t h y l e n e p r o d u c t i o n (Abeles and A b e l e s 1972). I t would t h e r e f o r e appear t h a t t h e p o r t i o n s o f tomato f r u i t s i n j u r e d by r a d i a n t energy t r e a t m e n t s s t i l l c o n t a i n e d l i v i n g c e l l s . The o r i g i n o f e t h y l e n e i n b o t h s t r e s s e d and u n s t r e s s e d t i s s u e s have been c o n s i d e r e d t o be s i m i l a r and t h e y may be d e r i v e d from the same p r e c u r s o r , m e t h i o n i n e ( A b e l e s and A b e l e s 1972, Hanson and Kende 1976, Hyodo 1977, Mapson e t a l . 1970). A n o t h e r f a c t o r t h a t has been shown i n r e c e n t y e a r s t o i n c r e a s e t h e r a t e o f e t h y l e n e p r o d u c t i o n i s w a t e r s t r e s s (McMichael e t a l . 1972, A d a t o and G a z i t 1974). In t h e p r e s e n t s t u d y , i t i s v e r y p o s s i b l e t h a t t h e s u s t a i n e d h i g h r a t e o f e t h y l e n e p r o d u c t i o n a f t e r t h e c l i m a c t e r i c peak i n t h e i n j u r e d f r u i t s was p a r t l y promoted by h i g h m o i s t u r e l o s s . Immediate-l y a f t e r t r e a t m e n t , m o i s t u r e l o s s r e s u l t i n g from r a d i a n t e n e r g y t r e a t m e n t s was always h i g h e r i n i n j u r e d f r u i t s t h a n i n the u n i n j u r e d c o n t r o l s ( F i g . 2 2 ) . A l t h o u g h i n subsequent s t o r a g e t h e r a t e o f m o i s t u r e l o s s d i d n o t d i f f e r g r e a t l y , on a c u m u l a t i v e b a s i s the m o i s t u r e l o s s i n f r u i t s exposed t o r a d i a n t energy was p r o b a b l y s u f f i c i e n t t o cause a w a t e r d e f i c i t s t r e s s i n t h e i n j u r e d f r u i t s . Water d e f i c i t s t r e s s has been found t o h a s t e n r i p e n i n g and advance t h e a p p e a r a n c e o f the peak o f e t h y l e n e p r o d u c t i o n and r e s p i r a t i o n i n avocado f r u i t s (Adato and G a z i t 1974). I t seems, t h e r e f o r e , t h a t w h i l e w a t e r s t r e s s would r e s u l t i n b o t h i n c r e a s e d e t h y l e n e p r o d u c t i o n as w e l l as the a c c e l e r a t i o n o f t h e c l i m a c t e r i c peak i n i n j u r e d f r u i t s , r i p e n i n g was p r e v e n t e d i n s t o r a g e because t h e mechanisms o f c a r o t e n o i d ( l y c o p e n e ) s y n t h e s i s and p e c t i c s o l u b i l i z a t i o n were a l r e a d y damaged by r a d i a t i o n t r e a t m e n t s b e f o r e s t o r a g e . T h i s a l s o e x p l a i n s why s t o r a g e t r e a t m e n t s were n o t e f f e c t i v e i n r e m o v i n g t h e i n j u r y . The r e s u l t s o f p r e v i o u s s t u d i e s by o t h e r w o r k e r s i n d i c a t e t h a t r i p e n i n g f a i l u r e i n f r u i t s i s due t o l a c k o f e t h y l e n e p r o d u c t i o n . F a i l u r e o f ' B a r t l e t t ' p e a r s t o r i p e n a t 40°C was a t t r i b u t e d t o l a c k o f e t h y l e n e p r o d u c t i o n and l o s s o f s e n s i t i v i t y t o t h e gas (Maxie e t a_l. 1974) . L i p t o n (1970) a l s o s u g g e s t e d t h a t r i p e n i n g f a i l u r e o f tomato f r u i t s f o l l o w i n g e x p o s u r e t o s o l a r r a d i a t i o n was p r o b a b l y due t o t h e i n h i b i t i o n o f e t h y l e n e p r o d u c t i o n by s h o r t - w a v e r a d i a t i o n . - 168 -Lipton did not determine ethylene production i n that study. However, a very recent study by Peiser and Yang (1979) has shown that l i g h t suppresses the increased ethylene production by sulfur-dioxide injured plants. A l l of these reports are contrary to the evidence presented i n t h i s i nvestigation. As shown e a r l i e r in the r e s u l t s , ethylene was produced and, i n f act, production was enhanced by injury (Fig. 20). It would be r e c a l l e d that f r u i t s used i n gas exchange determination, were stored at 12 hour photoperiod in growth cabinets. Hence, i t can be concluded that l i g h t does not suppress the increased ethylene production r e s u l t i n g from the radiant energy-induced injury, i n tomato f r u i t s . Control of Injury The evidence presented i n t h i s study shows that injury i s associated with the loss of two major mechanisms: carotenoid synthesis and pectic s o l u b i l i z a t i o n , both of which are involved in normal f r u i t ripening. The t r a d i t i o n a l methods employed to control ripening i n f r u i t s include: temperature regulation; the use of l i g h t to increase colour development i n the tomato (Jen 1974, Khudairi 1972, McCollum 1954, Vetter et a l . 1971); acceleration of ripening by exogenous application of ethylene; improvement of firmness by post-harvest calcium dips of whole f r u i t s (Lidster et a l . 1978, Mason et a l . 1974) and addition -169 ~ of calcium s a l t s i n canned f r u i t s (Kertesz 1949, Gould and Davies1954); the use of auxins (Lampe 1971) and other chemical growth regulators such as cupric ethylene diamine tetraacetate (CuEDTA) and f> -hydroxyethyl hydrazine (BOH) . Auxins generally delay ripening while calcium s a l t s improve firmness. The use of auxin,calcium s a l t s or ethylene was inappropriate i n the present circumstances. Lycopene synthesis was prevented i n the injured portion of f r u i t s and there was no s i g n i f i c a n t change i n firmness es p e c i a l l y following storage. The loss of the two mechanisms was not due to lack of ethylene production. Storage treatments employing various photoperiod, temperature regimes and oxygen concentration did not reverse sunscald whenever i t occurred on tomato f r u i t s (Table 17). Oxygen i s required for optimum carotenoid synthesis (McCollum 1954). The lower number of f r u i t s with detectable injury at 10°C compared with t h e i r warm controls was due to the slower ripening rate of the f r u i t s at low temperatures. Injury less than the " i n c i p i e n t " type showsup as yellowish-green area and i s d i f f i c u l t to detect on f r u i t s unless the uninjured portions are allowed to ripen. In a l l cases, injury, rather than being eliminated,became more v i s i b l e in storage i r r e s p e c t i v e of photoperiod,temperature regime and oxygen concentration. It i s thus clear that e f f o r t s aimed at the control of the injury must be placed on prevention instead of cure. - 170 -SUMMARY AND CONCLUSIONS T h i s s t u d y was c a r r i e d out t o i n v e s t i g a t e the c a u s e s and t h e p h y s i o l o g i c a l c h a r a c t e r i s t i c s o f a p o s t -h a r v e s t s u n s c a l d d i s o r d e r o f tomato f r u i t s . Emphasis was p l a c e d o n : ( i ) the r o l e s o f v i s i b l e , and i n f r a r e d r a d i a t i o n as w e l l as h i g h a i r t e m p e r a t u r e s , i n c a u s i n g the development o f the d i s o r d e r ; ( i i ) the e f f e c t s o f the d i s o r d e r on f r u i t t e x t u r e , l y c o p e n e , a s c o r b i c a c i d , p r o t o p e c t i n c o n t e n t s , and f r u i t pH; and ( i i i ) the p o s t - h a r v e s t gas exchange p r o c e s s e s o f f r u i t s f o l l o w i n g t h e i r e x p o s u r e t o i n j u r i o u s e l e c t r o m a g n e t i c r a d i a t i o n . In a d d i t i o n , the a b i l i t y o f s t o r a g e t e m p e r a t u r e , p h o t o p e r i o d and oxygen c o n c e n t r a t i o n t o a l l e v i a t e t h e i n j u r y was a l s o examined. From t h e r e s u l t s o b t a i n e d d u r i n g t h e i n v e s t i g a t i o n , t h e f o l l o w i n g c o n c l u s i o n s can be drawn: 1. D i r e c t e x p o s u r e o f h a r v e s t e d tomato f r u i t s t o i n t e n s e r a d i a n t e n e r g y w i l l cause s u n s c a l d i n j u r y . . The s e v e r i t y o f t h e i n j u r y i n c r e a s e s w i t h i n c r e a s i n g d u r a t i o n o f e x p o s u r e and i n c r e a s i n g i r r a d i a n c e . 2. The e f f e c t i v e n e s s o f t h e r a d i a n t e n e r g y c a u s i n g i n j u r y depends m a i n l y on the amount o f r a d i a t i o n i n the i n f r a r e d waveband. - 1 7 1 -3. The a c t i o n o f i n f r a r e d r a d i a t i o n i s t h e r m a l r a t h e r t h a n p h o t o c h e m i c a l . I n f r a r e d r a d i a t i o n i s more e f f e c t i v e t h a n v i s i b l e r a d i a t i o n o r h i g h a i r t e m p e r a t u r e s i n i n d u c i n g a r i s e i n f r u i t t e m p e r a t u r e . H i g h a i r t e m p e r a t u r e s a l o n e can cause most o f t h e symptoms o f s u n s c a l d i n j u r y e x c e p t t h a t t h e f r u i t s u r f a c e becomes g r e y i s h r a t h e r t h a n w h i t i s h c o l o u r c h a r a c t e r i s t i c o f f r u i t s e x p o s e d t o r a d i a n t e n e r g y . 4. P h o t o o x i d a t i o n does h o t appear t o be a p r e -r e q u i s i t e f o r i n j u r y d e v e l o p m e n t . I n j u r y d e v e l o p s i n f r u i t s i r r a d i a t e d i n t h e absence o f oxygen o r i n f r u i t s k e p t i n d a r k n e s s a t h i g h a i r t e m p e r a t u r e s . 5. I n j u r y can be i n d u c e d a t a l l s t a g e s o f r i p e n e s s . I t s t a r t s w i t h t h e f o r m a t i o n o f t r a n s p a r e n t p e r i c a r p on t h e exposed s i d e o f t h e f r u i t . Green f r u i t s become b l e a c h e d . As i n j u r y a d v a n c e s , s e m i - r i p e and r i p e f r u i t s show some i n t e r n a l foaming and e p i c a r p r u p t u r e , w h i l e t h e s u r f a c e o f g r e e n f r u i t s becomes w r i n k l e d . 6. G e n e r a l l y , i n j u r y i n c r e a s e s f r u i t d e f o r m a t i o n , p e r i c a r p s t r e n g t h , c o m p l i a n c e and t o u g h n e s s . I t a l s o m i n i m i s e s changes i n mesocarp r e s i s t a n c e and f i r m n e s s d u r i n g r i p e n i n g . Among t h e s i x p h y s i c a l t e x t u r a l c h a r a c t e r i s t i c s w h i c h were m e a s u r e d , o n l y t o u g h n e s s was i n s e n s i t i v e t o changes due t o f r u i t r i p e n e s s . Toughness i s t h e r e f o r e c o n s i d e r e d t o be i n a p p r o p r i a t e f o r t h e d e t e c t i o n o f t e x t u r a l changes r e s u l t i n g from f r u i t r i p e n e s s i n t o m a t o e s . - 172 -7. I n j u r y p r e v e n t s p r o t o p e c t i n s o l u b i l i z a t i o n , p r e s u m a b l y by c a u s i n g enzyme i n a c t i v a t i o n . P r o t o p e c t i n c o n t e n t i s w e l l c o r r e l a t e d w i t h f o u r f o r c e - d e f o r m a t i o n c h a r a c t e r i s t i c s : p e r i c a r p s t r e n g t h , mesocarp r e s i s t a n c e , c o m p l i a n c e and f i r m n e s s (R >• . 7 8 ) . However, i n t h e p r e s e n c e o f i n j u r y , c o m p l i a n c e seems t o be t h e b e s t p r e d i c t o r o f 2 p r o t o p e c t i n c o n t e n t (R = 90.4%, = 1.97) i r r e s p e c t i v e o f t h e s t a g e o f r i p e n e s s . I t i s t h e r e f o r e c o n c l u d e d t h a t c o m p l i a n c e i s t h e b e s t c h a r a c t e r i s t i c f o r use i n d e t e c t i n g changes i n t e x t u r e o f tomato f r u i t s , due t o s u n s c a l d i n j u r y . 8. I n j u r y c a u s e s a marked d e c r e a s e i n a s c o r b i c • a c i d c o n t e n t and t h i s change o c c u r s p r o g r e s s i v e l y d u r i n g t h e development o f i n j u r y . P o s t - i n j u r y r i p e n i n g does n o t overcome t h e l o s s o f a s c o r b i c a c i d . I n j u r e d f r u i t s s h o u l d t h e r e f o r e be c o n s i d e r e d a p o o r s o u r c e o f v i t a m i n C . 9. I n j u r y i n c r e a s e s f r u i t p H . S i n c e t h e p r o c e s s i n g i n d u s t r y r e q u i r e s h i g h a c i d i t y f o r good r e t e n t i o n o f p r o d u c t c o l o u r , f l a v o u r and t e x t u r e , tomato f r u i t s w i t h s u n s c a l d i n j u r y s h o u l d be c o n s i d e r e d u n s u i t a b l e f o r p r o c e s s i n g . 10. The mode o f a c t i o n o f r a d i a n t e n e r g y i n p r e v e n t i n g f r u i t c o l o u r development a p p e a r s t o be by d e s t r u c t i o n o f the mechanism o f l y c o p e n e s y n t h e s i s , r a t h e r t h a n by a c c e l e r a t i o n o f l y c o p e n e d e g r a d a t i o n . - 173 -11. F a i l u r e o f f r u i t s t o r i p e n n o r m a l l y i s n o t due t o l a c k o f e t h y l e n e p r o d u c t i o n . I n j u r y o f t h e magnitude l e s s t h a n t h e " i n c i p i e n t " t y p e , a c c e l e r a t e d t h e o n s e t o f t h e c l i m a c t e r i c and r i p e n i n g . "Advanced" type o f i n j u r y r e d u c e d t h e r a t e o f r e s p i r a t i o n d u r i n g f r u i t r i p e n i n g , b u t i n c r e a s e d t h e r a t e o f e t h y l e n e p r o d u c t i o n . 12. The r e l a t i o n s h i p between t h e r a t e o f r e s p i r a t i o n and t h e r a t e o f e t h y l e n e p r o d u c t i o n i s s h i f t e d by i n j u r y . M o i s t u r e l o s s may c o n t r i b u t e t o t h e i n c r e a s e d r a t e o f e t h y l e n e p r o d u c t i o n i n i n j u r e d f r u i t s . 13. S t o r a g e t r e a t m e n t s i n v o l v i n g d i f f e r e n t p h o t o p e r i o d and oxygen c o n c e n t r a t i o n s d i d n o t a l l e v i a t e i n j u r y . I t i s t h e r e f o r e recommended t h a t t o c o n t r o l s u n s c a l d i n j u r y , emphasis s h o u l d be p l a c e d on t h e p r e v e n t i o n o f e x p o s u r e o f f r u i t s t o i n t e n s e e l e c t r o m a g n e t i c r a d i a t i o n r a t h e r t h a n a t t e m p t s t o c u r e i n j u r y f o l l o w i n g e x p o s u r e . - 174 BIBLIOGRAPHY A b e l e s , A . L . and F . B . A b e l e s . 1972. 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Mechanisms o f p r o t e c t i o n o f t r e h a l a s e a g a i n s t h e a t i n a c t i v a t i o n i n N e u r o s p o r a . B a c t e r i o l o g y 94: 1306-1312. Z s c h e i l e , F . P . and J . W . P o r t e r . 1947. A n a l y t i c a l methods f o r c a r o t e n e s o f l y c o p e r s i c o n s p e c i e s and s t r a i n s . A n a l . Chem. 19: 47-51. - 194 -APPENDIX. SPECTRAL INTENSITY FOR LAMP NO. 490. M i c r o v / a t t s p e r ( S t e r a d i a n - M i l l i m i c r o n ) v s . W a v e l e n g t h , 2800° K. C o l o r T e m p e r a t u r e T u n g s t e n Ribbon Wavelength I n t e n s i t y (nm) 380 116.1 400 179. 0 425 284.6 450 422.5 475 592.0 500 792.9 525 1013.0 550 1269.3 575 1526.6 600 1785.9 625 2049.3 650 2302.5 675 2541.7 700 2767.7 725 2977.6 750 3158.2 Wavelength I n t e n s i t y (nm) 800 3450.8 850 3671.8 900 3789.8 950 3840.3 1000 3825.1 1050 3753.5 1100 3645.5 1150 3532.5 1200 3403.4 1250 3254.0 1300 3099.6 1350 2928.1 1400 2772.7 1450 2601.2 1500 2450.9 1550 2307.6 - 195 -CALIBRATION OF THE ISCO SPECTRORADIOMETER P h o t o m e t r i c D i s t a n c e = 30 cm. Amperes S e t t i n g = 16.16 4.6 v o l t s SR S p e c t r o r a d i o m e t e r was p l a c e d i n a h o r i z o n t a l p o s i t i o n b e s i d e t h e ISCO M o d e l SRC S p e c t r o r a d i o m e t e r C a l i b r a t o r so t h a t t h e p l a n e o f t h e f i l a m e n t was p a r a l l e l t o the d i f f u s i n g s c r e e n . The s u p p l i e d S p e c t r a l I n t e n s i t y v a l u e s f o r s t a n d a r d lamp #490 (Appendix) were d i v i d e d by (30 cm)2 t o o b t a i n t h e S p e c t r a l Energy i m p i n g i n g on £he d i f f u s i n g s c r e e n and t h u s u n i t s o f uW cm - 2 nm" d e s i g n a t e d S, were o b t a i n e d . A S D C A S D C 380 129 075 1.72 750 3.509 4.2 0.835 400 199 # 12 1. 66 800 3.834 3.8 1.008 425 316 34 0.93 850 4.079 3.7 1.102 450 469 60 0.78 900 4.211 3.75 1.123 475 658 m 97 0. 678 950 4.267 3.85 1.108 500 m 881 1. 5 0. 587 1000 4.251 3.95 1.076 525 1. 126 1. 8 0. 625 1050 4.170 4.35 0. 958 550 1. 410 2. 3 0. 613 1100 4. 051 4. 65 0. 871 575 1. 696 3. 1 0.547 1150 3.925 4.5 0. 872 600 1. 984 3. 4 0.583 1200 3.782 4 . 0 0. 945 625 2. 277 3. 7 0.615 1250 3.616 4.75 0.761 650 2. 558 3. 9 0. 655 1300 3. 444 6.5 0.529 675 2. 824 4. 2 0. 672 1350 3.253 7.0 0. 465 700 3. 075 4. 8 0. 641 1400 3.081 5.5 0.560 725 3. 308 4. 7 0.704 1450 2. 890 4.75 0. 608 750 3. 509 4. 4 0.797 1500 2.723 5.9 0. 462 775 1550 2.564 7.35 0.349 where S = S t a n d a r d V a l u e a t s p e c i f i c -2 -1. D = D i r e c t R e a d i n g on c = _ S _ u W c m _ 2 n m _ 1 S p e c t r o r a d i o m e t e r D (uW cm nm ) c = c o r r e c t i o n F a c t o r A = Wavelength (nm) 

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