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Effect of fruit calcium on breakdown in Spartan apples Lidster, Perry David 1976

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THE EFFECT OF F E U I T CALCIUM ON BREAKDOWN I N SPARTAN APPLES by PERRY DAVID LIDSTE.R B. S c . (Agr.) UNIVERSITY o f B R I T I S H COLUMBIA ,1972 A THESIS SUBMITTED I N PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES DEPARTMENT OF PLANT SCIENCE Wa a c c e p t t h i s t h e s i s a s c o n f o r m i n g t o t h e r e g u i r e d s t a n d a r d THE UNIVERSITY OF B R I T I S H COLUMBIA August, 1976 @ P e r r y David L i d s t e r , 1976 In present ing t h i s t he s i s in p a r t i a l f u l f i l m e n t o f the requirements f o r an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree that the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r reference and study. I f u r t h e r agree that permiss ion fo r ex ten s i ve copying of t h i s t he s i s f o r s c h o l a r l y purposes may be granted by the Head of my Department or by h i s r ep re sen ta t i ve s . It i s understood that copying or p u b l i c a t i o n o f t h i s t he s i s f o r f i n a n c i a l gain s h a l l not be a l lowed without my w r i t t e n permis s ion. Department of The Un i v e r s i t y of B r i t i s h Columbia 2075 Wesbrook P l a c e Vancouver, Canada V6T 1W5 11 ABSTRACT The e f f e c t of s e v e r a l methods of calcium a p p l i c a t i o n on the f r u i t c a l c i um content, f r u i t firmness, and break-down i n c i d e n c e i n Spartan apples was s t u d i e d . Prebloom c a l c i u m sprays d i d not i n c r e a s e f r u i t calcium l e v e l s or reduce breakdown i n c i d e n c e . The a p p l i c a t i o n of s t r o n t i u m or boron i n c o n j u n c t i o n with calcium sprays, d i d not reduce breakdown i n c i d e n c e other than that expected from the calcium sprays alone. A 4 percent calcium c h l o r i d e postharvest d ip decreased breakdown i n c i d e n c e over a range of f r u i t weights and breakdown p o t e n t i a l s . The p o s t h a r v e s t dip f a i l e d to g i v e t o t a l breakdown c o n t r o l and d i d not have a s i g n i f i c a n t e f f e c t on f r u i t firmness. Low (73%-80% RH) and high (94% RH) storage h u m i d i t i e s lowered the i n i t i a l r a t e of calcium p e n e t r a t i o n i n t o the f r u i t t i s s u e s . Moderate storage h u m i d i t i e s (87% RH) r e s u l t e d i n the most r a p i d i n i t i a l uptake of calcium by the t i s s u e s . The humidity e f f e c t on calcium-45 accumulation by the f r u i t t i s s u e s decreased with time i n storage. i i i TABLE OF CONTENTS Abs t r a c t . i i L i s t of Tables v L i s t of F i g u r e s . v i Acknowledgements . v i i I n t r o d u c t i o n 1 Calcium Related Storage D i s o r d e r s 1 S o i l F a c t o r s A f f e c t i n g Calcium A v a i l a b i l i t y ......5 Calcium T r a n s l o c a t i o n to the F r u i t ,...8 Calcium F u n c t i o n Within F r u i t 14 Other Calcium E f f e c t s on F r u i t T i s s u e 16 E f f e c t of complementary Ions on F r u i t Calcium ....17 App l i e d Calcium versus F r u i t Calcium and F r u i t D i s o r d e r s .. 23 O b j e c t i v e s of Present Study . 25 M a t e r i a l s and Methods ..........27 Experiment 1 .......28 Experiment 2 . 30 Experiment 3 31 Experiment 4 ........31 Experiment 5 33 Experiment 6 ........33 Re s u l t s .35 Experiment 1 35 Experiment 2 ...35 Experiment 3 ..35 Experiment 4 .................................. 36 i v Experiment 5 .37 Experiment 6 .. ......39 D i s c u s s i o n .. .41 Experiment 1 .......41 Experiment 2 .........42 Experiment 3 ..43 Experiment 4 45 Experiment 5 ......47 Experiment 6 50 Summary 53 L i t e r a t u r e C i t e d 56 L I S T OF TABLES E f f e c t of prebloom lime sprays on f r u i t c a l c i um and breakdown i n c i d e n c e 8.3 Breakdown versus s i l v e r t i p c a l c i u m c h l o r i d e sprays ..84 E f f e c t of boron and c a l c i u m sprays on f r u i t calcium and breakdown 85 E f f e c t of calcium and strontium sprays on f r u i t f irmness and breakdown .....86 Percent breakdown and f r u i t calcium content versus calcium c h l o r i d e a p p l i c a t i o n 87 E f f e c t of storage time on calcium-45 uptake 88 E f f e c t of storage humidity on calcium-45 p e n e t r a t i o n 89 LIST OF FIGURES i g u r e 1. Scattergram of percentage breakdown i n f r u i t dipped i n calcium c h l o r i d e versus c o n t r o l . ....90 2. Scattergram of percentage breakdown versus f r u i t s i z e (gm) i n f r u i t dipped i a calcium c h l o r i d e 91 3. Scattergram of f l e s h f i r m n e s s i n f r u i t dipped i n c a l c i um c h l o r i d e versus that i n c o n t r o l f r u i t .92 4. Scattergram of percentage breakdown i n c o n t r o l f r u i t versus f r u i t s i z e (gm) .........93 v i i ACKNOWLEDGEMENTS I would l i k e to thank Dr. S.W. P o r r i t t and Dr. G. W. Eaton without whose support t h i s study program would not have been completed. The advice given by Dr. V.C. Runeckles and Dr. P.A. J o l l i f f e i n p r o v i d i n g d i r e c t i o n and encouragement i s g r a t e f u l l y acknowledged. A s p e c i a l thanks to B. Downing and B. Drought f o r t h e i r d e d i c a t e d t e c h n i c a l a s s i s t a n c e throughout the du r a t i o n of t h i s study. F i n a n c i a l support was provided by the NEC I n d u s t r i a l Research A s s i s t a n c e Program 128 which was issued through B.C.Tree F r u i t s L t d . , 1473 Water S t r e e t , Kelowna, B.C. 1 INTRODUCTION Calcium_Relat ied„St rO iraqe j_ aD The S p a r t a n v a r i e t y has been a r e l a t i v e l y r e c e n t i n t r o d u c t i o n d a t i n g back t o 1926. A c r o s s between Newtown and M c i n t o s h , t h e c u l t i v a r f o u n d i t s way t o t h e recommended p l a n t i n g l i s t i n 1936. I n t h e i n i t i a l y e a r s t h e S p a r t a n c u l t i v a r showed much p r o m i s e and p l a n t i n g s were i n c r e a s e d r a p i d l y . Breakdown was not c o n s i d e r e d t o be a s e r i o u s d e f e c t a t t h a t t i m e , b u t as a c r e a g e s i n c r e a s e d and more S p a r t a n s were b e i n g s t o r e d , breakdown s o o n became a t h r e a t t o f u r t h e r S p a r t a n e x p a n s i o n . S p a r t a n breakdown has been r e c o r d e d a s e a r l y a s 1949 and t h e i n c i d e n c e o f breakdown has been f o u n d t o f l u c t u a t e from y e a r t o y e a r a t random. As a c o n s e g u e n c a , t h e S p a r t a n c u l t i v a r has been removed f r o m t h e recommended p l a n t i n g l i s t s i n 1952, 1964, and 1971. The h e s i t a n c y o f t h e Okanagan f r u i t i n d u s t r y t o a b s o r b t h e 10 t o 20 m i l l i o n d o l l a r l o s s i n p h a s i n g o u t t h e S p a r t a n v a r i e t y , has r e s u l t e d i n s u b s t a n t i a l S p a r t a n p l a n t i n g s and an a n n u a l m i l l i o n b u s h e l S p a r t a n c r o p . The d e l a y . i n r e m o v a l o f S p a r t a n t r e e s w i l l p r o v e p r o f i t a b l e o n l y i f breakdown c a n be r e l i a b l y c o n t r o l l e d . The r o l e o f h i g h l e v e l s o f endogenous f r u i t c a l c i u m i n p r e v e n t i n g a p p l e d i s o r d e r s has bean w e l l documented. Low c a l c i u m l e v e l s i n t h e f r u i t have been a s s o c i a t e d w i t h 2 the development of b i t t e r p i t (Garman and Ma t t h i s 1956; Martin et a l . 1960; Martin et a l . 1962; Ki d s t o n et a l . 1963; Pienaar et a l . 1964), senescent breakdown ( P e r r i n g 1968; Bangerth et a l . 1972; Bangerth 1973), low temperature breakdown (P e r r i n g 1968; Bangerth 1973), l e n t i c e l breakdown ( P e r r i n g 1968), a c c e l e r a t e d r e s p i r a t i o n r a t e s and s o f t e n i n g (Bangerth et a l . 1973; Bramlage et a l . 1974; Faust and Shear 1972) and t h e o r e t i c a l l y l i n k e d to water core i n d u c t i o n ( P e r r i n g 1968). P e r r i n g suggested t h a t the development of c a l c i u m - r e l a t e d p h y s i o l o g i c a l d i s o r d e r s i n f r u i t may r e s u l t from e i t h e r a low endogenous calcium content or an imbalance of potassium, magnesium, n i t r o g e n , and calcium. High l e v e l s of f r u i t potassium, magnesium or n i t r o g e n i n r e l a t i o n to the calcium content may r e s u l t i n the same f r u i t d i s o r d e r s which are a s s o c i a t e d with d e f i c i e n t calcium l e v e l s . Many i n v e s t i g a t o r s have found t h a t the a p p l i c a t i o n of calcium decreases the i n c i d e n c e of b i t t e r p i t (Van Goor 1971; Marti n and Lewis 1972; Terblanche and Myburgh 1971; Chittenden et a l . 1972; Mattus 1972), low temperature breakdown ( W i l l s et a l . . 1969), i n t e r n a l or senescent breakdown (Martin et a l . 1971; Dewey 1972a; Dewey and D i l l e y 1974; S c o t t and W i l l s 1975), Jonathan spot (Fukuda 1969, 1972), a c e t i c a c i d p r oduction ( S i l l s et a l . 1961) and i n c r e a s e s c e l l membrane p e r m e a b i l i t y (fiousseau et a l . 1972; Van Goor 1971) . Spartan breakdown, which manifests i t s e l f i n the 3 Okanagan f r u i t i n d u s t r y , has a negative c o r r e l a t i o n with f r u i t c a l c i um content (Mason and McDougald 1974; L i d s t e r et a l . 1975) s i m i l a r to that found f o r b i t t e r p i t , i n t e r n a l or senescent breakdown, low temperature breakdown and water core. The symptoms a s s o c i a t e d with Spartan breakdown are u n l i k e any of the other f r u i t d i s o r d e r s mentioned. Spartan breakdown i s a senescent type of storage breakdown which develops i n i t i a l l y i n the hypodermal l a y e r of the apple f r u i t . The d i s o r d e r f i r s t appears as a f a i n t d i f f u s e browning of the f l e s h immediately beneath the apple epidermis o f t e n beginning at a point source. The a f f e c t e d brown t i s s u e w i l l c o n t i n u e to spread to encompass the e n t i r e apple. Vascular s t r a n d s , w i t h i n the apple f l e s h a f f e c t e d by breakdown, appear dark brown and are a prominent f e a t u r e i n d i s t i n g u i s h i n g Spartan breakdown from b r u i s e s and other c o i n c i d e n t a l f l e s h brownings. The p h y s i o l o g i c a l events which r e s u l t i n the m a n i f e s t a t i o n of spartan breakdown have not been c l e a r l y i d e n t i f i e d . However, the strong r e l a t i o n s h i p of c a l c i u m to breakdown development suggests t h a t the l a c k of c a l c i u m i s i n v o l v e d with the physiology of the d i s o r d e r . The p h o s p h o l i p i d s of the c e l l membrane are capable of b i n d i n g c a l cium ions to c r e a t e an e l e c t r o s t a t i c membrane charge (Koketsu et a l . 1964). The calcium adsorbed to the c e l l u l a r membrane i s e s s e n t i a l to provide the s e l e c t i v e p e r m e a b i l i t y c h a r a c t e r i s t i c s of c e l l membranes (Bangerth 4 1974). As f r u i t c e l l s age, the calcium a s s o c i a t e d with the c e l l u l a r membranes may be d i s p l a c e d from the b i n d i n g s i t e s and become s o l u b l e . The c e l l membranes would then become •leaky', l o s i n g t h e i r s e l e c t i v e p e r m e a b i l i t y , and a l l o w i n g the v a c u o l a r s u b s t r a t e s t o mix with the c y t o p l a s m i c enzymes. The polypheholoxidase enzymes found w i t h i n the cytoplasm may o x i d i z e the c e l l u l a r s u b s t r a t e s and produce the brown d i s c o l o r a t i o n a s s o c i a t e d with Spartan breakdown development. The Okanagan crop years of 1964, 1969 and 1970 i n c u r r e d heavy l o s s e s due t o Spartan breakdown. Spartan f l e s h c a l c ium c o n c e n t r a t i o n s vary among crop years. Years of low f r u i t c a l c i um l e v e l s appear to be r e l a t e d to years of high breakdown i n c i d e n c e (S.W. P o r r i t t , p e r s o n a l communication). In these years, breakdown was found a f t e r two to t h r e e months storage i n commercial c o l d s t o r a g e s operated with h u m i d i t i e s ranging from 75% SH to 85% RH. Under s i m i l a r s torage c o n d i t i o n s i n the remaining crop years s i n c e 1960, Spartan breakdown was not g e n e r a l l y observed at the c o n c l u s i o n of f i v e months. Storage h u m i d i t i e s g r e a t e r than 90% RH r e s u l t i n higher breakdown i n c i d e n c e s than low storage h u m i d i t i e s (75-80% RH) ( P o r r i t t and Meheriuk 1973; P o r r i t t et a l . 1975). F r u i t calcium appears to be the most c r i t i c a l m ineral n u t r i e n t i n f l u e n c i n g the development of Spartan breakdown, b i t t e r p i t and senescent breakdown. 5 Most of the endogenous calcium enters a f r u i t t r e e through the root system. The amount of calcium which e n t e r s the t r e e system by a b s o r p t i o n through the r o o t s may be a f f e c t e d by e i t h e r e x t e r n a l s o i l f a c t o r s ( T i s d a l e and Nelson 1969) or i n t e r n a l , c e l l u l a r f a c t o r s (Link 1974). The f r u i t t r e e may r e c e i v e minor doses of calcium from i r r i g a t i o n water, s o i l p a r t i c l e s blown about by the wind. F r u i t t r e e r o o t s absorb calcium from the c a t i o n exchange complex or s o i l c alcium i n s o l u t i o n . S o i l moisture content, s o i l pH, s o i l a e r a t i o n , s o i l temperature, s o i l type and the c o n c e n t r a t i o n of calcium and the presence of elements a n t a g o n i s t i c to calcium uptake are a l l a b l e to i n f l u e n c e calcium a v a i l a b i l i t y t o the r o o t s ( T i s d a l e and Nelson 1969). Soluble s o i l c a l c i um i s c o n s t a n t l y i n t e r c h a n g i n g with the calcium bound to the s o i l c o l l o i d p a r t i c l e s . S o i l drought c o n d i t i o n s r e s t r i c t the amount of s o l u b l e c a l c i u m a v a i l a b l e f o r r o o t uptake because the c a l c i u m p r e c i p i t a t e s out as c a l c i u m carbonate (CaC03) or calcium phosphate Ca (P04) 2. The s o i l c a l c i um content i n humid regions i s decreased by constant l e a c h i n g of the s o l u b l e and exchangeable forms. Extreme high or low s o i l pH w i l l g r e a t l y r e s t r i c t the a v a i l a b l e c a l cium i n the s o i l (Truog 1946). S o i l pH below 6.0 i s e f f e c t i v e i n reducing the calcium a v a i l a b l e f o r f r u i t t r e e growth. As s o i l pH decreases, c a l c i u m i s 6 d i s p l a c e d from t h e c a t i o n exchange complex by h y d r o g e n i o n s . The f r e e s o i l c a l c i u m i o n s can be: 1/ l o s t i n d r a i n a g e w a t e r s , 2/ a b s o r b e d by o r g a n i s m s , 3/ a d s o r b e d o n t o s u r r o u n d i n g c l a y p a r t i c l e s , o r 4/ r e p r e c i p i t a t e d as a s e c o n d a r y c a l c i u m compound ... ( T i s d a l e and N e l s o n 1969) . I n c r e a s e s i n s o i l pH g r e a t e r t h a n 9.0 w i l l r e d u c e t h e a v a i l a b l e c a l c i u m s u p p l y by t h e f o r m a t i o n o f i n s o l u b l e c a l c i u m p h o s p h a t e s . The i d e a l s o i l pH l e v e l f o r f r u i t t r e e g r o w t h and optimum c a l c i u m a v a i l a b i l i t y i s i n t h e r e g i o n o f pH 6.0-8.0 ( S w a l e s 1971). The s o i l must be s u f f i c i e n t l y p o r o u s t o a l l o w a e r a t i o n . F r u i t t r e e r o o t s r e q u i r e l a r g e volumes o f a i r i n t h e s o i l t o c a r r y on t h e i r n o r m a l r e s p i r a t i o n , g r o w t h and a b i l i t y t o a b s o r b water and n u t r i e n t s ( M i l l a r and Turk 1943) . S o i l t e m p e r a t u r e w i l l g r e a t l y i n f l u e n c e t h e s o i l c a l -c ium a v a i l a b i l i t y . s o i l c a l c i u m m a i n t a i n s a dynamic r e l a t i o n s h i p among t h e p r e c i p i t a t e , e x c h a n g e a b l e c a l c i u m and t h e s o l u b l e c a l c i u m f o r m s . L o w e r i n g t h e s o i l t e m p e r a t u r e would c a u s e a s h i f t t o t h e p r e c i p i t a t e form and r e n d e r c a l c i u m u n a v a i l a b l e . The d e g r e e o f c a l c i u m a v a i l a b i l i t y t o the f r u i t t r e e i s g r e a t l y a f f e c t e d by t h e s o i l t y p e . S o i l s w i t h a h i g h f r a c t i o n o f 2:1 t y p e c l a y s r e l e a s e l e s s c a l c i u m t h a n s o i l s w i t h a h i g h f r a c t i o n o f 1:1 t y p e c l a y s . C o a r s e t e x t u r e d 7 s o i l s have few exchange s i t e s and allow the c a l c i u m to be f r e e l y leached out by water. S o i l s high i n organic matter o f t e n have l e s s a v a i l a b l e c a l c i u m as much of the s o l u b l e c a l c i u m i s adsorbed to exchange s i t e s on the o r g a n i c f r a c t i o n . The c o n c e n t r a t i o n of s o i l calcium w i l l most l i k e l y i n f l u e n c e the amount of a v a i l a b l e calcium when the o v e r a l l c o n c e n t r a t i o n f a l l s below c r i t i c a l growth l e v e l s . k s u r p l u s s o i l c a l c i um supply does not i a p l y a g r e a t e r supply of a v a i l a b l e calcium to the t r e e r o o t s . Many i n v e s t i g a t o r s have added calcium to orchard s o i l s and have not found f r u i t calcium l e v e l s t o be i n c r e a s e d (Martin and Carne 1950) or r e l a t e d storage d i s o r d e r s to be decreased (Beyers 1963; Martin et a l . 1965; Mason 1973; Redmond 1975). Chittenden at a l . (1963) found a s l i g h t i n c r e a s e i n b i t t e r p i t f o l l o w i n g s o i l ap-p l i c a t i o n s of gypsum and lime. Baxter (1960), Mattus (1972), and Van Schreven (1963) a p p l i e d c a l c i u m n i t r a t e or gypsum to the s o i l and found s i g n i f i c a n t r e d u c t i o n s i n b i t t e r p i t . Hilkenbaumer and Kohl (1958) and Pianaar et a l . (1971) found repeated s o i l a p p l i c a t i o n s of c a l c i u m t o reduce b i t t e r p i t and i n c r e a s e f r u i t calcium. In cases where s o i l c alcium i s d e f i c i e n t , the a d d i t i o n of calcium to the s o i l may i n c r e a s e f r u i t calcium l e v e l s and reduce calcium r e l a t e d d i s o r d e r s by r e p l e n i s h i n g the c a t i o n exchange complex and s o i l s o l u b l e calcium supply. However, i f s u f f i c i e n t c a l c ium i s present i n the s o i l but i s 8 rendered u n a v a i l a b l e because of low s o i l pH or a l a r g e number of a n t a g o n i s t i c i o n s , then the a d d i t i o n of calcium to the s o i l w i l l have l i t t l e e f f e c t on the t r e e calcium supply to the f r u i t and may correspond to the s i t u a t i o n observed by Beyers (1963) and Martin et a l . (1965) .. Singh and Halstead (1973) determined the s o i l a p p l i c a t i o n of calcium as lime d i d not i n c r e a s e the amount of exchangeable ca l c i u m , but the a p p l i c a t i o n of c a l c i u m sulphate (gypsum) in c r e a s e d exchangeable calcium l e v e l s . The b e n e f i c i a l e f f e c t of adding gypsum to the s o i l may r e s u l t from the a d d i t i o n of s u l f u r rather than c a l c i u m (Singh and Halstead 1973). Excess s o i l calcium w i l l be leached from the s o i l or p r e c i p i t a t e d i n t o i n s o l u b l e and u n a v a i l a b l e forms. Potassium, magnesium or hydrogen i o n s may decrease calcium a v a i l a b i l i t y , to the t r e e r o o t s , i f they are present i n l a r g e amounts. High l e v e l s of e i t h e r potassium, magnesium, or hydrogen may r e p l a c e calcium on the c a t i o n exchange complex and render calcium l e a c h a b l e . The r e s u l t a n t s o i l w i l l be calcium d e f i c i e n t . C a l e i u m _ T r a n s l o c a t i o n In the process of being absorbed by the r o o t s calcium must t r a v e r s e the root epidermis, cortex, endodermis, and v a s c u l a r parenchyma. Uptake of calcium i n v o l v e s an a c t i v e exchange process across the root c e l l membranes. Link 9 (1974) i n d i c a t e d t h a t calcium movement i n t o the root c o n s i s t s of two phases: 1/ a r a p i d r e v e r s i b l e accumulation of s o i l c alcium on the root exchange s i t e s , f o l l o w e d by 2/ a slow s u s t a i n e d accumulation of calcium on the t r a n s f e r exchange s i t e s which i s dependent on calcium removal from w i t h i n the r o o t . Most of the calcium which has been absorbed by the ro o t s e n t e r s the xylera f o r t r a n s l o c a t i o n t o the l e a v e s , wood and f r u i t . The phloem, however, i s capable of slow calcium movement (Stebbins and Dewey 1972) and accounts f o r only a f r a c t i o n of the t o t a l calcium t r a n s l o c a t e d (Link 1974). The calcium i s t r a n s l o c a t e d w i t h i n the xylem by a s e r i e s of exchange s i t e s which are s e n s i t i v e to the metabolic demands of a c t i v e t i s s u e ( B e l l and Biddulph 1963). Rapid mass flow movement of calcium has l a r g e l y been d i s c o u n t e d as the s o l e method of c a l c i u m t r a n s l o c a -t i o n i n p l a n t s ( B e l l and Biddulph 1963). Shear and Faust (1971) have determined calcium to be t r a n s l o c a t e d i n apple s e e d l i n g s at a r a t e of approximately 10 cm per day, which i s much slower than would be expected f o r mass flow movement of calcium. Faust and Shear (1973) have determin-ed some t r a n s p i r a t i o n a l e f f e c t on calcium movement a f t e r a pe r i o d of water s t r e s s suggesting some movement of calcium by the xylem. Research at the East M a i l i n g Research S t a t i o n has de-termined M7, M16, M25, M104, MM109, and MM111 r o o t s t o c k s to be i n e f f i c i e n t i n absorbing s o i l calcium. M2 and MM106 10 r o o t s t o c k s a r e i n t e r m e d i a t e t o H9, M13, and M27 w h i c h a r e c o n s i d e r e d t o be e f f i c i e n t c a l c i u m a b s o r b i n g r o o t s t o c k s (B. W a t k i n s , p e r s o n a l c o m m u n i c a t i o n ) . K o k s a l (1975) a l s o f o u n d t h a t M 7 r o o t s t o c k r e s t r i c t e d c a l c i u m a c c u m u l a t i o n by J o n a t h a n , C o x ' s Orange P i p p i n a n d B o s k o o p f r u i t f r o m t h a t f o u n d w i t h R 11 r o o t s t o c k . F r u i t grown on a M 9 r o o t s t o c k h a d h i g h e r c a l c i u m l e v e l s t h a n f r u i t grown on a H 7 r o o t s t o c k ( K o k s a l 1 9 7 5 ) . R. G r a n g e r ( p e r s o n a l c o m m u n i c a t i o n ) , u s i n g n u t r i e n t s o l u t i o n c u l t u r e o b s e r v e d M7 t o r e s t r i c t c a l c i u m movement t o t h e u p p e r p a r t o f t h e t r e e s y s t e m . F a u s t e t a l . (1971) f o u n d c a l c i u m a c c u m u l a -t i o n t o v a r y among a p p l e s e e d l i n g s a n d s u g g e s t t h e p o t e n -t i a l f o r c a l c i u m u p t a k e a nd t r a n s l o c a t i o n may v a r y g r e a t l y among a p p l e c u l t i v a r s . C u l t i v a r s s u c h a s S p a r t a n o r G o l d e n D e l i c i o u s , w h i c h a r e v a r y s u s c e p t i b l e t o b r e a k d o w n a nd b i t t e r p i t r e s p e c t i v e l y , may be u n a b l e t o a c c u m u l a t e c a l -c i u m t o t h e same e x t e n t a s non s u s c e p t i b l e c u l t i v a r s , s u c h a s D e l i c i o u s ( E a t o n and R o b i n s o n 1 9 7 5 ) . The d e v e l o p i n g a p p l e f r u i t r e c e i v e s a l a r g e i n f l u x o f c a l c i u m v i a t h e x y l e m d u r i n g f o u r t o f i v e weeks o f f r u i t c e l l d i v i s i o n i m m e d i a t e l y f o l l o w i n g f r u i t s e t ( T e t l e y 1930; S m i t h 1 9 5 0 ; W i l k i n s o n 1968; H i l l i k a n 1 9 7 1 ) . D u r i n g c e l l e x p a n s i o n , t h e f r u i t c e l l u l a r a c t i v i t y s u b s i d e s and t h e demand f o r m e t a b o l i c c a l c i u m d e c r e a s e s . A t t h i s p o i n t , when t h e d e v e l o p i n g f r u i t a p p r o x i m a t e s 30 grams, t h e c a l -c i u m s u p p l y t o t h e f r u i t s h i f t s f r o m t h e x y l e m t o t h e p h l o e m (Wiersum 1966; Van Go o r 1971; S t e b b i n s a nd Dewey 11 1972) . At f i v e weeks from bloom, c e l l d i v i s i o n ceases and f u r t h e r f r u i t growth i s due to c e l l enlargement (Smith 1950). Calcium uptake f a i l s to p a r a l l e l f r u i t growth and the calcium c o n c e n t r a t i o n w i t h i n the f r u i t i s d i l u t e d with f r u i t growth. Although calcium c o n t i n u e s t o enter the f r u i t v i a the phloem, the calcium p r e v i o u s l y l o c a t e d within the f r u i t may be r e t r a n s l o c a t e d i n t o the surrounding leaves (Martin 1967; Wilkinson 1968). At t h i s stage of f r u i t development the f r u i t s erves as a calcium pool which maintains an e g u i l i b r i u m between the wood, f r u i t and l e a f t i s s u e s . The adjacent d e v e l o p i n g leaves and shoots, which are m e t a b o l i c a l l y a c t i v e , are able t o exert a g r e a t e r demand on the calcium- supply than the f r u i t . Nearby de v e l o p i n g l e a v e s and shoots are able to withdraw o n e - f i f t h of the t o t a l f r u i t c a l c i u m content d u r i n g the p e r i o d from c e l l expansion to f r u i t m aturity (Wilkinson 1968; P e r r i n g 1968, 1975). N i n e t y - f i v e percent of the calcium i n j e c t e d i n t o a branch e i g h t weeks p r i o r to h a r v e s t was l o c a t e d i n the l e a v e s and buds which suggests an overwhelming demand on the calcium supply by n o n - f r u i t t i s s u e s (Lewis and Martin 1973) . Martin (1971) was able to i n c r e a s e the calcium content of Merton apples from 174 to 239 ppm and reduce b i t t e r p i t i n c i d e n c e by lowering the t r a n s p i r a t i o n l o s s from the l e a v e s . During the p e r i o d when calcium i s r a p i d l y s u p p l i e d to the developing f r u i t by the xylem, the calcium i s evenly o 12 d i s t r i b u t e d throughout the f r u i t (Wieneke 1974). As the c a l c i u m supply i s r e s t r i c t e d by the s h i f t from the xylem to the phloem, calcium g r a d i e n t s w i t h i n the apple become apparent and i n c r e a s e i n magnitude u n t i l apple maturity (Lewis and Martin 1973). F l e s h calcium content nearest the p o i n t of entry i n t o the apple (stem end) was the highest and d e c l i n e d s t e a d i l y towards the c a l y x end (Lewis and Martin 1973). Calcium c o n c e n t r a t i o n was a l s o higher i n the core r e g i o n and near the v a s c u l a r bundles than i n the c o r t e x t i s s u e s . T h i s p a t t e r n of calcium d i s t r i b u t i o n w i t h i n apple f r u i t s i s c o n s i s t e n t with the o b s e r v a t i o n of P o r r i t t (personal communication) of Spartan breakdown developing i n the c o r t e x t i s s u e of the c a l y x end. The amount of calcium remaining i n the f r u i t at the time of harvest w i l l be a f u n c t i o n o f : 1/ the t o t a l amount of c a l -cium r e c e i v e d d u r i n g the p e r i o d of c e l l d i v i s i o n , and 2/ the amount of metabolic a c t i v i t y of the t i s s u e s surrounding the f r u i t . Fuhr and Hieneke (1974) have shown ca l c i u m a p p l i e d i n the previous crop year w i l l overwinter i n the t r e e and be a v a i l a b l e f o r t r a n s l o c a t i o n i n t o the new developing f r u i t l e t . A c a l c i u m pool may e x i s t within the t r e e and may be responsive to calcium a p p l i e d as sprays. I n c r e a s i n g the l e v e l of calcium w i t h i n the t r e e system by prebloom l i m a or calcium c h l o r i d e sprays may i n c r e a s e the i n i t i a l c a l c i -um supply to the f r u i t and r e s u l t i n i n c r e a s e d calcium content i n the mature f r u i t . The calcium s t r e s s p l a c e d on 13 the f r u i t may be reduced by removing nearby a c t i v e l y d i v i d i n g l e a v e s and shoots (Perring and Preston 1974). Link (1974) i n d i c a t e d the development of b i t t e r p i t was p o s i t i v e l y c o r r e l a t e d to the l e a f s u rface a r e a / f r u i t r a t i o and to the amount of carbohydrates produced by the surrounding l e a v e s . Calcium movement i n t o the apple may be r e s t r i c t e d by the formation of i n s o l u b l e c a l c ium oxalate c r y s t a l s i n the apple p e d i c l e (Stebbins et a l . 1972). Redmond and Bould (1972) found apple stems to r e s t r i c t calcium movement i n to the apple. The apple stems maintained very high l e v e l s of water i n s o l u b l e calcium which i s very s i m i l a r to that observed by Stebbins et a l . (1972). Chang et a l . (1968) found higher temperatures to r e s u l t i n g r e a t e r calcium i m m o b i l i z a t i o n i n the stems of tobacco p l a n t s . Stebbins et a l . (1972) d i s c u s s e d the f o r m a t i o n of o x a l a t e c r y s t a l s as p o s s i b l y b l o c k i n g the movement of c a l -cium i n t o the f r u i t and r e s u l t i n g i n low l e v e l s of f r u i t c a l c ium. However, as the f r u i t r e c e i v e s most of i t s c a l c i -um very e a r l y i n the f r u i t development, the f o r m a t i o n of o x a l a t e c r y s t a l s may very well prevent l o s s e s of f r u i t c a lcium to the surrounding l e a f t i s s u e s . The argument proposed by Stebbins et a l . (1972) may not be e n t i r e l y v a l i d . 14 Calcium l o c a t e d w i t h i n the f r u i t has a number of s t r u c t u r a l and p h y s i o l o g i c a l f u n c t i o n s . Calcium may form b r i d g e s between adjacent c e l l wall p e c t i n s and serve to bind adjacent c e l l w a l l s (Bangerth 1974). Bangerth et a l . (1972) suggested that as the f r u i t matures, the calcium j o i n i n g the p e c t a t e chains i s r e l e a s e d and i n d i v i d u a l c e l l s become uncoupled. The s e p a r a t i o n of the c e l l s i s a s s o c i a t e d with the d e c l i n e of f r u i t f l e s h f i r m n e s s . I n -c r e a s i n g f r u i t calcium l e v e l s by the a p p l i c a t i o n of sprays or dips may maintain f r u i t f l e s h firmness by p r e v e n t i n g the calcium which forms the pe c t a t e b r i d g e s from becoming s o l u b l e (Poovaiah and Leopold 1973). Calcium i s e s s e n t i a l f o r the maintenance of the d i f f e r e n t i a l p e r m e a b i l i t y and the s t r u c t u r a l i n t e g r i t y of the c e l l u l a r membranes (Marinos 1962; Wilkinson and Morre 1973; Mahanty and Fineran 1975). C e l l u l a r membranes are r e s p o n s i b l e f o r i o n a b s o r p t i o n and r e l e a s e s e l e c t i v i t y of the c e l l ( E pstein 1961; Manery 1966). The r e s u l t s of Van Steveninck (1965) supported the hypothesis of Bennett and R i d e a l (1954) i n which the ca l c i u m adsorbed to the a n i o n i c m o i e t i e s on the o u t s i d e o f the plasma membrane and not the s t r u c t u r a l calcium found w i t h i n the membrane, was c r i t i c a l i n m a intaining s e l e c t i v e p e r m e a b i l i t y . The a p p l i c a t i o n of calcium t o c e l l u l a r s t r u c t u r e s can i n h i b i t the p r o g r e s s i o n of membrane l e a k i n e s s and can even r e v e r s e the process i f 15 i t has not passed a c r i t i c a l stage (Van Steveninck 1965; Van Goor 1968, 1971). The decrease i n the d i f f e r e n t i a l p e r m e a b i l i t y of the plasma membrane and t o n o p l a s t i n a calcium d e f i c i e n t s t a t e , w i l l r e s u l t i n the l o s s of c e l l u l a r compartmentalization and le a d to the mixing of cytop l a s m i c enzymes and vacuolar s u b s t r a t e s (Sacher 1966). Loss of c e l l u l a r membrane i n t e g r i t y w i l l lead to i n c r e a s e d r e s p i r a t i o n r a t e s , a c c e l e r a t e d r i p e n i n g , and an i n c r e a s e i n the onset of p h y s i o l o g i c a l d i s o r d e r s which may be reversed by the a p p l i c a t i o n of calcium (Rousseau et a l . 1972; Bangerth et a l . 1972). Faust and Shear (1972) observed the r e s p i r a t i o n r a t e of York I m p e r i a l apples to be n e g a t i v e l y c o r r e l a t e d with f l e s h calcium content below 140 ppm. Faust and K l e i n (1974) i n d i c a t e d calcium i n f u s e d i n t o the apple d i s c s , was able to reduce r e s p i r a t i o n r a t e and i n c r e a s e p r o t e i n s y n t h e s i s . Bramlage et a l . (1974) found t h a t the calcium l e v e l s of the f r u i t s k i n were n e g a t i v e l y c o r r e l a t e d with the maximum r a t e of C02 p r o d u c t i o n during the c l i m a c t e r i c peak. The ca l c i u m e f f e c t i n depressing the r e s p i r a t i o n r a t e i s one of maintaining c e l l u l a r i n t e g r i t y , which subsequently slows the r a t e of r i p e n i n g and suppresses the development of c a l c i u m - r e l a t e d p h y s i o l o g i c a l d i s o r d e r s . 16 Mitochondria may a c t i v e l y accumulate c a l c i u m and undergo i n c r e a s e d r e s p i r a t o r y a c t i v i t y (Truelove and Hanson 1966). Snay and Bramlage (1969) found that calcium added to m i t o c h o n d r i a l p r e p a r a t i o n s may reduce or i n c r e a s e r e s p i r a t o r y a c t i v i t y depending upon the procedure used. I n c r e a s i n g f r u i t c a l c i u m was found to r a i s e the a s c o r b i c a c i d l e v e l s by 20-40% i n Cox's Orange P i p p i n and Jonathan apples and 4 to 6 times i n low a s c o r b i c a c i d Golden D e l i c i o u s (Bangerth 1974). The exact a c t i o n of c a l -cium i n i n c r e a s i n g v i t a m i n C l e v e l s i n apples i s unknown, but presumably calcium i n h i b i t s the c a t a b o l i s m of a s c o r b i c a c i d . Calcium can f u n c t i o n i n the i n h i b i t i o n of one ATPase (Bangerth 1974) and the a c t i v a t i o n of another membrane a s s o c i a t e d ATPase (Rasmussen 1970) and amylase (Jones' and Yarner 1967) . Dela Fuente and Leopold (1973) determined calcium c o u l d r e - e s t a b l i s h normal auxin t r a n s p o r t i n sunflower subseguent t o calcium c h e l a t i n g treatment. The i n t e n s i t y of auxin t r a n s p o r t i s s e v e r e l y r e s t r i c t e d i n cal c i u m -d e p l e t e d t i s s u e but the v e l o c i t y remains unchanged. Dela Fuente and Leopold (1973) used t h i s as evidence t h a t c a l -cium d i d not a f f e c t auxin t r a n s p o r t s i t e s s p e c i f i c a l l y but maintains membrane s t r u c t u r a l i n t e g r i t y necessary f o r normal volumes of auxin t r a n s p o r t . 17 The e f f e c t s of calcium on m i t o c h o n d r i a l f u n c t i o n , f r u i t a s c o r b i c a c i d c o n t e n t , enzyme a c t i v i t y and auxin t r a n s p o r t are not c l e a r l y a s s o c i a t e d with the development of the c a l c i u m - r e l a t e d d i s o r d e r s of b i t t e r p i t , senescent breakdown or Spartan breakdown. E f f e c t _o£_Comp_lement^ The c a l c i u m supply to the f r u i t and the u l t i m a t e f r u i t c a l c i um content i s g r e a t l y i n f l u e n c e d by the type and c o n c e n t r a t i o n of ions a n t a g o n i s t i c to calcium uptake, t r a n s l o c a t i o n , and c e l l u l a r f u n c t i o n . Trees which r e c e i v e d n i t r o g e n i n the ammonium form have lower f r u i t c alcium values than f r u i t with n i t r o g e n s u p p l i e d as n i t r a t e {Shear and Faust 1970; Faust and Shear 1972). Anderson and Jackson (1968) found n i t r a t e n i t r o g e n s u p p l i e d to wheat s e e d l i n g s i n c r e a s e d the uptake and t r a n s l o c a t i o n of calcium. The s t i m u l a t o r y e f f e c t of n i t r o -gen f e r t i l i z a t i o n on ca l c i u m uptake and t r a n s l o c a t i o n occurred between the t h i r d and t w e l f t h hour a f t e r the n i -trogen was a p p l i e d . Presumably, the uptake and t r a n s l o c a -t i o n of calcium may ba i n h i b i t e d i n a calcium d e f i c i e n t s t a t e and s u p p l y i n g n i t r o g e n would r e i n s t a t e normal c a l c i -um t r a n s l o c a t i o n . A l t e r n a t i v e l y , the ammonium or n i t r a t e i o n may d i s p l a c e calcium on the xylem exchange s i t e s i n i t i a l l y and r e s u l t i n a surge of calcium movement over a sho r t p e r i o d . A displacement of calcium ions from the 18 exchange s i t e s would a g r e e w i t h t h e c o n c l u s i o n s o f F a u s t and S h e a r (1973). F e r t i l i z e r n i t r o g e n a p p l i e d a s ammonium s u l f a t e o r u r e a has an a c i d i f y i n g e f f e c t on t h e s o i l and may i n c r e a s e t h e s o l u b i l i t y o f s o i l c a l c i u m (Truog 1946) and e x c h a n g e a b l e c a l c i u m s u p p l i e s ( T i s d a l e and N e l s o n 1 9 6 9 ) . The c a l c i u m i o n s removed f r o m t h e exchange s i t e s may e i t h e r be p r e c i p i t a t e d o r l e a c h e d o u t i n low s o i l pH c o n d i t i o n s . C a l c i u m n i t r a t e when us e d as a f e r t i l i z e r m a i n t a i n s t h e s o i l pH n e a r n e u t r a l i t y and s u p p l i e s b o t h c a l c i u m and n i t r a t e t o t h e p l a n t . However c a l c i u m n i t r a t e i s l e s s e f f i c i e n t i n s u p p l y i n g n i t r o g e n t o t h e p l a n t t h a n i s ammonium s u l f a t e o r u r e a on a per pound b a s i s . P l a n t s w i t h exchange s i t e s s a t u r a t e d by h y d r o g e n i o n s from n u t r i e n t s o l u t i o n s a t pH 2 c o u l d n o t t r a n s p o r t c a l c i -um ( F a u s t and S h e a r 1973). P r e s u m a b l y , t h e ammonium i o n i s a b l e t o s i m i l a r l y i n h i b i t c a l c i u m t r a n s l o c a t i o n t o t h e f r u i t . C a l c i u m t r a n s l o c a t i o n c an be r e i n s t a t e d by r a i s i n g t h e c a l c i u m g r a d i e n t from t h e n u t r i e n t s o l u t i o n to t h e l e a v e s and f r u i t (Shear and F a u s t 1970). Xylem t r a n s p o r t o f c a l c i u m a p p e a r s t o be p r o p o r t i o n a l t o t h e s i z e o f t h e c a l c i u m g r a d i e n t a l o n g t h e r o o t - l e a f a x i s . M a r t i n e t a l . (1966) d e t e r m i n e d t h a t h i g h n i t r o g e n l e v e l s w i t h i n a p p l e f r u i t s i n c r e a s e d t h e s u s c e p t i b i l i t y t o s e n e s c e n t breakdown i n f o u r a p p l e c u l t i v a r s . I t i s d i f f i c u l t t o d e t e r m i n e whether t h e h i g h f r u i t n i t r o g e n l e v e l s m e r e l y r e f l e c t e d d i f f e r e n c e s i n f r u i t s i z e and 19 subsequently f r u i t calcium c o n c e n t r a t i o n with breakdown i n c i d e n c e . Faust (1975) determined that f r u i t r a t i o s g r e a t e r than 20 ppm n i t r o g e n t o 1 ppm calcium w i l l r e s u l t i n f r u i t breakdown. The f r u i t n i t r o g e n to calcium r a t i o should not exceed 10 to 1 to maintain good f r u i t q u a l i t y and storage l i f e (Faust 1975) The presence of s o l u b l e aluminum ions at low s o i l pH w i l l decrease r o o t calcium uptake i n wheat s e e d l i n g s (Johnson and Jackson, 1964, Foy et a l . 1967). S o l u b l e aluminum may d i s l o c a t e calcium adsorbed on the s o i l exchange complex ( T i s d a l e and Nelson 1969). Aluminum i o n s may a l s o become attached to the c e l l u l a r membranes of p l a n t r o o t s thus n e u t r a l i z i n g membrane sur f a c e charges necessary f o r calcium uptake (Clarkson and Sanderson 1971) . Strontium, an element s i m i l a r to calcium, may compete with calcium i o n s f o r s i t e s on the s o i l c a t i o n exchange complex (Jacobson and o v e r s t r e e t 1948). The accumulation of strontium by p l a n t s i s d i r e c t l y p r o p o r t i o n a l to the s o i l exchangeable strontium and i n v e r s e l y p r o p o r t i o n a l to the s o i l calcium content (Collander 1941; Meazel and Heald 1959; and Mayberry 1962). Strontium i s s i m i l a r to calcium i n that the accumulation of strontium decreases as the s o i l a c i d i t y i n c r e a s e s and that the t o t a l amount of s t r o n -tium found i n l e a v e s i s p r o p o r t i o n a l to l e a f age (Rediske and E l d e r s 1953). Although the d i s t r i b u t i o n of s t r o n t i u m w i t h i n a plant i s s i m i l a r to that of calcium (Martin et 20 a l . 1957), strontium i s unable to perform the same physio-l o g i c a l f u n c t i o n s as c a l c i u m , and strontium accumulations w i l l r e s u l t i n calcium d e f i c i e n c y symptoms and t i s s u e i n j u r y (Hurd-Karrer 1939; da S i l v a 1962). High l e v e l s of strontium s u p p l i e d to the r o o t s or f r u i t may competetively i n h i b i t the f u n c t i o n of c a l c i u m i n preventing the development of b i t t e r p i t and breakdown. Wolf and Cesare (1952) found s t r o n t i u m a p p l i e d as a spray to peach t r e e s moved r e a d i l y i n t o l e a f t i s s u e s . Woodbridge et a l . (1974) determined t h a t low l e v e l s of boron i n n u t r i e n t s o l u t i o n s l i m i t e d calcium a b s o r p t i o n by apple s e e d l i n g s . At low n u t r i e n t s o l u t i o n l e v e l s of c a l c i u m , the e f f e c t of low boron l e v e l s i n l i m i t i n g c a l c i -um a b s o r p t i o n was l e s s e n e d . High boron l a v e l s i n the n u t r i e n t s o l u t i o n s were c o r r e l a t e d with high calcium l e v e l s i n the t i s s u e s (Branchley and Warington 1927; Woodbridge et a l . 1974) ,. A s y n e r g i s t i c e f f e c t of boron on f r u i t c a l c i u m content appears to be evident (Garman and Mathis 1956). Shear and Faust (1970) found that l e a f c a l -cium values i n c r e a s e d with the a p p l i c a t i o n of 1.6 x 10 _3M b o r i c a c i d . Mattus (1972) observed that two e a r l y season s o l u b l e boron sprays e f f e c t i v e l y reduced the i n c i d e n c e of cork spot. P e r r i n g (1968) suggested t h a t f r u i t phosphorus l e v e l s may be p o s i t i v e l y c o r r e l a t e d to senescent breakdown i n Cox's Orange P i p p i n s . F r u i t phosphorus l e v e l s below a c r i t i c a l l e v e l of 8 mg/100 gram of t i s s u e may r e s u l t i n 21 breakdown even at high c a l c i u m l e v e l s . Martin et a l . (1976) found t h a t h a l v i n g the phosphorus supply t o apple t r e e s grown i n pot c u l t u r e r e s u l t e d i n lower f r u i t c a l c i um and magnesium l e v e l s . Trees grown i n the absence of phosphorus f a i l e d t o produce f r u i t (Martin et a l . 1967). F r u i t magnesium and potassium ions are a n t a g o n i s t i c to the f u n c t i o n of calcium i n p r e v e n t i n g the development of senescent d i s o r d e r s . The an t a g o n i z i n g e f f e c t of potassium and magnesium on the a c t i o n of c a l c i u m i n pr e v e n t i n g b i t t e r p i t appears on l y when calcium l e v e l s are d e f i c i e n t i n f r u i t s (Bangerth 1974). Antagonism of the f u n c t i o n of calcium by potassium and magnesium i s more l i k e l y to occur i n apple f r u i t than i n apple l e a v e s as the r a t i o of potassium p l u s magnesium to calcium i n l e a v e s approximate 1-2 to 1, whereas i n the f r u i t the r a t i o approximates 20-50 to 1 (Bangerth 1974). The main c e l l u l a r f u n c t i o n of calcium appears t o be the maintenance of the d i f f e r e n t i a l p e r m e a b i l i t y of the c e l l u l a r membranes (Rousseau et a l . 1972) by n e u t r a l i z i n g the a n i o n i c b i n d i n g s i t e s on the o u t s i d e of the membrane. The r e l a t i v e f r a c t i o n s of each c a t i o n adsorbed on the membrane w i l l be a f u n c t i o n o f : 1/ the r e l a t i v e c oncentra-t i o n of the c a t i o n s immediately surrounding the a n i o n i c s i t e s , and 2/ the a f f i n i t y of each c a t i o n to the b i n d i n g s i t e s (Bangerth 1974). The a f f i n i t i e s of hydrogen, calcium, magnesium, and potassium f o r rad blood c e l l membrane a n i o n i c b i n d i n g 22 s i t e s were determined-to be: potassium was approximately one hundred times l e s s than e i t h e r calcium or magnesium which were approximately one hundred times l e s s than hydrogen i o n s (Carvalho and Sanui 1963). The r e l a t i v e con-c e n t r a t i o n of these ions i n apple a r e : 1 hydrogen 10—*H, calcium 10 - 3M, and•potassium 5-8 x 10-2M. Hydrogen i o n s should g r e a t l y antagonize the a d s o r p t i o n of membrane c a l -cium c o m p e t i t i v e l y . F r u i t c e l l s with low pH v a l u e s may have more ca l c i u m r e p l a c e d by hydrogen i o n s . Less calcium adsorbed to the c e l l membranes may cause the l o s s of s e l e c t i v e p e r m e a b i l i t y . True (1922) i n i t i a l l y d e s c r i b e d the the antagonism of calcium by magnesium i n p l a n t t i s s u e s . M i l l i k a n (1972) de-termined that calcium and magnesium g r a d i e n t s e x i s t w i t h i n apple f r u i t s and have found magnesium l e v e l s to be e i g h t times g r e a t e r than calcium i n the c a l y x end of some apple f r u i t s . S i m i l a r g r a d i e n t s f o r potassium may e x i s t i n apple f r u i t s (Bangerth 1974). Although the a n i o n i c a f f i n i t y f o r potassium i s approximately one hundred times l e s s than f o r calcium, the average f r u i t potassium l e v e l s may be f o r t y to f i f t y times g r e a t e r than f r u i t calcium l e v e l s (personal o b s e r v a t i o n ) . Bangerth (1974) suggests that potassium l e v e l s may i n c r e a s e s i g n i f i c a n t l y r e l a t i v e to the calcium l e v e l s at the end of the xylem v e s s e l s as potassium e x h i b i t s a high m o b i l i t y i n apple (Van Goor and Wiersma *At pH 4 23 1974). Van Goor (1971) has shown that potassium t r a n s p o r t to the apple f r u i t i s l i n e a r throughout f r u i t development and causes f r u i t potassium t o c a l c i u m r a t i o s to s t e a d i l y i n c r e a s e a f t e r c e l l d i v i s i o n . i£2lied_Calcium_Versus_Fruit_ S o i l c a l c i u m a p p l i c a t i o n s give u n p r e d i c t a b l e r e s u l t s i n i n c r e a s i n g f r u i t c alcium l e v e l s and decreasing f r u i t d i s o r d e r s , s o i l l i m i n g i s most o f t e n used to c o r r e c t a c i d orchard s o i l s (Neufeld 1973) which w i l l i n t u r n i n c r e a s e the source of s o l u b l e and exchangeable s o i l c alcium f o r t r e e growth (Truog 1946). Supplementing f r u i t c a l c i u m l e v e l s by p r e h a r v e s t calcium sprays or postharvest calcium d i p s i s more e f f i c i e n t than s o i l l i m i n g i n reducing f r u i t d i s o r d e r s (Martin et a l 1968; Chittenden et a l . 1972; Van Goor 1971; Mason e t a l . 1974). There are s e v e r a l c a l c i u m compounds which can be a p p l i e d as s p r a y s and d i p s . Calcium c h l o r i d e , c a l c i u m n i t r a t e and c a l c i u m hydroxide (carbonate) have been used i n s p e c i f i c a p p l i c a t i o n s . Concentrations of calcium c h l o r i d e sprays of g r e a t e r than 0.6 percent (wt/wt) w i l l r e s u l t i n l e a f margin burn. Both calcium n i t r a t a and lime sprays r e s u l t i n l e s s l e a f burn than the same concentra-t i o n s of calcium c h l o r i d e . However, the s o l u b i l i t y of lime (calcium hydroxide) i s 0.185 percent (wt/wt) and w i l l l i m i t the r a t e of lime a p p l i c a t i o n . S l u r r i e s of lime 24 approaching two percent may be a p p l i e d by commercial spr a y e r s . The s o l u b i l i t i e s of calcium c h l o r i d e and calcium n i t r a t e are 74.5 and 121.2 percent (wt/wt) r e s p e c t i v e l y and do not r e p r e s e n t p r a c t i c a l l i m i t a t i o n s t o the concen-t r a t i o n of spray a p p l i c a t i o n . Sprays of calcium n i t r a t e have the added advantage of s u p p l y i n g n i t r a t s n i t r o g e n f o r t r e e growth. Fukuda (1972) determined that four midsummer sprays of 0.38 percent calcium c h l o r i d e i n c r e a s e d Jonathan f l e s h c a l c i u m content to 320 ppm (dry weight) whereas four sprays of 0.5 percent c a l c i u m n i t r a t e or 1.2 percent lime water (CaO) i n c r e a s e d the f l e s h content to 260 ppm as compared to a c o n t r o l l e v e l of 220 ppm. Mason (1971) observed t h a t seven sprays of 15 pounds of c a l c i u m c h l o r i d e per acre i n c r e a s e d Spartan f l e s h calcium by 35 ppm over the non-sprayed c o n t r o l . Seven sprays of 15 pounds per acre of calcium n i t r a t e i n c r e a s e d the f r u i t f l e s h c a l c ium content by 6 ppm. Calcium c h l o r i d e sprays are a p p a r e n t l y more e f f i c i e n t i n r a i s i n g f r u i t c a l c i um l e v e l s than are calcium n i t r a t e sprays or lime s p r a y s . The lower e f f i c i e n c y of calcium n i t r a t e sprays i n r a i s i n g f r u i t calcium l e v e l s may account f o r the lack of a s i g n i -f i c a n t e f f e c t on f r u i t c a l c i um l e v e l s and d i s o r d e r i n c i -dence found by Stevenson (1967) and Dewey (1972). k s i n g l e one percent calcium n i t r a t e preharvest spray a p p l i e d two or three weeks p r i o r t o h a r v e s t was found to be e f f e c t i v e i n reducing b i t t e r p i t and r a i s i n g f r u i t calcium l e v e l s 25 (Martin et e l . 1968, 1971). A f o u r percent postharvest calcium c h l o r i d e d i p i s capable of r a i s i n g Spartan f r u i t calcium l e v e l s by 40 to 75 ppm (Mason 1973; Mason et a l . 1974) whereas seven summer sprays of 0.6 percent calcium c h l o r i d e r e s u l t e d i n s m a l l e r i n c r e a s e s i n f r u i t c alcium content of 20 to 40 ppm (Mason 1971). Postharvest calcium c h l o r i d e d i p s are e f f e c t i v e i n i n c r e a s i n g f r u i t calcium l e v e l s and reducing breakdown i n Jonathan (Dewey 1972b), Cox's Orange P i p p i n and Twenty Ounce apples (Scott and W i l l s 1975) . The magnitude of calcium uptake from a p o s t h a r v e s t dip i s r e l a t e d to the apple c u l t i v a r dippad (Martin and Lewis 1967), the calcium c o n c e n t r a t i o n of the d i p p i n g s o l u t i o n (Mason 1974; Scott and W i l l s 1975), and the d i p p i n g s o l u t i o n temperature (Scott and W i l l s 1975). 2 k i s c t i v e s _ o f _Present_StudjA The purpose of t h i s study was to i n v e s t i g a t e d i f f e r e n t pre- and postharvest methods of i n c r e a s i n g the c o n c e n t r a t i o n of calcium i n Spartan apple and the e f f e c t s of added calcium on storage q u a l i t y and breakdown. The f o l l o w i n g areas were s t u d i e d i n d e t a i l i n s i x separate experiments: 1. The e f f e c t on f r u i t calcium and breakdown i n Spartan apple of s u p p l y i n g a r e s e r v o i r of c a l c i u m to t h e t r e e system and developing f r u i t l e t , by t r e e sprays. 26 2. The e f f e c t of added s o l u b l e boron to summer c a l c i -um sprays on f r u i t calcium l e v e l s and subsequent breakdown development. 3. The i n f l u e n c e of f o l i a r summer sprays of st r o n t i u m on f r u i t calcium c o n c e n t r a t i o n s , the development of Spartan breakdown and f l e s h firmness i n storage. 4. The r e l a t i v e e f f e c t i v e n e s s of calcium c h l o r i d e when a p p l i e d as 1/ three midsummer sprays of 0.5 percent calcium c h l o r i d e , 2/ one preharvest spray of two or fou r percent calcium c h l o r i d e , or 3/ one four percent post-harvest d i p , or u/ any combination of the three procedures on f r u i t c alcium content and breakdown i n c i d e n c e . 5. The e f f e c t i v e n e s s o f a fou r percent p o s t h a r v e s t calcium c h l o r i d e d i p i n re d u c i n g breakdown i n c i d e n c e and maintaining apple firmness. 6. The e f f e c t of storage humidity on the r a t a of c a l -cium p e n e t r a t i o n of calcium a p p l i e d as a d i p to Spartan apple f r u i t . 27 MATERIALS AND METHODS A l l f r u i t treatments were a p p l i e d to Spartan apples (Malus_p_umila M i l l . ) grown i n the Okanagan V a l l e y of B r i t i s h Columbia. Each i n d i v i d u a l experiment was completed i n commercial orchards of known breakdown poten-t i a l . F l a s h calcium l e v e l s were determined by the procedure developed by Drought {personal communication). I n d i v i d u a l f r u i t s were peeled and opposing s e c t o r s were removed. The s e c t o r s were a i r d r i e d at 21° C f o r two days and d r i e d t o constant weight i n a f o r c e d a i r oven f o r twenty f o u r hours at 60°C. The samples were removed and weighed immediately, as d r i e d f r u i t samples r a p i d l y absorb a i r moisture. The samples were h e r m e t i c a l l y s e a l e d i n p l a s t i c bags and f r o z e n . The samples were ground and r e p l a c e d i n h e r m e t i c a l l y s e a l e d bags at -18°C. A one gram sample of apple powder was removed, placed i n a 50 ml pyrex beaker and ashed f o r three hours at 575°C. The ash was taken up i n 25 ml of 6500 ppm lanthanum i n 0.5N HCI. The r e s u l t a n t s o l u t i o n was analyzed on a Techtron atomic a b s o r p t i o n spectrophotometer. One-bushel samples of approximately 80 f r u i t were harvested f o r breakdown assessments. The f r u i t was harves-ted at commercial maturity and placed i n 1.5 m i l p e r f o r a t e d p o l y e t h y l e n e l i n e r s which were se a l e d with 28 e l a s t i c bands. The p e r f o r a t e d poly l i n e r s maintained a storage humidity o f approximately 9U% RH without a f f e c t i n g carbon d i o x i d e or oxygen l e v e l s . The bagged f r u i t samples were placed i n common c o l d storage at -0.6°C. The d u r a t i o n of the storage p e r i o d was determined by the appearance o f low breakdown i n c i d e n c e i n the r e f r i g e r a t e d f r u i t . F r u i t samples were then removed from c o l d storage and incubated at 21°C f o r seven to ten days to o b t a i n f u l l development of breakdown symptoms. F r u i t firmness was measured on a t e n - f r u i t sample a t the , time of storage removal. A Magness-Taylor pressure t e s t e r with a 7/16 inch diameter t i p was used f o r a l l firmness determinations. The a n a l y s i s of the r e s u l t s of Experiment 5 was run as stepwise r e g r e s s i o n s . A l l other r e s u l t s r e p o r t e d were analyzed by a n a l y s i s of va r i a n c e and the Student-Nauman-Keuls t e s t . ISP.e£i!nent_l A) The e f f e c t of a prebloom calcium c h l o r i d e spray on f r u i t c a l c i u m content and breakdown i n c i d e n c e : Twenty t r e e s were s e l e c t e d from a commercial Spartan block of uniform age, s o i l type and r o o t s t o c k . The s e l e c t e d t r e e s were mapped i n t o a randomized complete block design (RCBD) of f i v e b l o c k s each c o n t a i n i n g f o u r treatments. S o l u t i o n s of 0.5, 1.5, and 2.5 percent calcium c h l o r i d e (wt/wt) plus 0.05 percent (wt/wt) Super Spread 2 29 s u r f a c t a n t ware a p p l i e d by a commercial handgun s p r a y e r to thoroughly wet the t r e e , a l l spray a p p l i c a t i o n s c o i n c i d e d with the one-half inch green stage of l e a f development. B) The e f f e c t of a prebloom lime spray on f r u i t c a l -cium content and breakdown i n c i d e n c e : a randomized complete block design (RCBD) was mapped i n homogeneous bl o c k s of s p a r t a n t r e s s i n each of three commercial orchards. The three orchards s e l e c t e d , were of high, moderate, and low breakdown p o t e n t i a l as i n d i c a t e d by past breakdown performances. Whole t r e e s were sprayed with a handgun sprayer to r u n o f f , with one s o l u t i o n o f : 1/ A 2 percent (wt/wt) s l u r r y of calcium hydroxide (lime) plus 0.05 percent s u r f a c t a n t , 2/ A 0.1 percent dormant o i l plus 2 percent s l u r r y of lime p l u s 0.05 percent s u r f a c t a n t , 3/ A 0.2 percent dormant o i l plus 2 percent lime plus 0.05 percent s u r f a c t a n t spray, 4/ A 0.1 percent c a s e i n plus 2 percent s l u r r y of lime p l u s 0.0 5 percent s u r f a c t a n t spray, 5/ A 0.1 percent soya bean f l o u r plus 2 percent s l u r r y of lime p l u s 0.05 percent s u r f a c t a n t spray, 6/ A 0.05 percent B i o - F i l m 3 plus 2 percent s l u r r y of lime spray, or 7/ A 4 percent (v/v) lime s u l f u r spray. 2Tradename of Niagara Chemical Co. ^Tradename of Rohm and H a r r i s Co. 30 8/ One c o n t r o l treatment which d i d not r e c e i v e any spray. i) The low breakdown r i s k o rchard RCBD c o n s i s t e d of f i v e b l o c k s with a l l e i g h t treatments a p p l i e d , i i ) The moderate breakdown r i s k o rchard RCBD c o n s i s t e d o f f i v e blocks with seven treatments a p p l i e d . The lime s u l f u r treatment was omitted as the grower d i d not want t o chance the p o s s i b l e l e a f damage a r i s i n g from t h i s spray, i i i ) The high breakdown r i s k orchard RCBD c o n s i s t e d of four blocks of seven treatments. The lime s u l f u r spray was e l i m i n a t e d . The e f f e c t of boron on f r u i t calcium uptake from midsummer calcium c h l o r i d e sprays was run as a RCBD c o n s i s t i n g of f i v e homogeneous b l o c k s with f o u r treatments each. The treatments were a p p l i e d to whole t r e e s by a com-m e r c i a l handgun sprayer u n t i l spray d r i p was observed. Each spray was a p p l i e d four times at two week i n t e r v a l s commencing August 14, 1974. The treatments* c o n s i s t e d of: 1/ 2.2 x 10 - 2M b o r i c a c i d plus 0.6 percent (wt/wt) commercial calcium c h l o r i d e (77-80%), 2/ 2.2 x 10~ 3M b o r i c a c i d plus 0.6 percent calcium c h l o r i d e . 4 A l l spray treatments i n c l u d e d 0.05% Super Spread s u r f a c t a n t . 31 3/ 2.2 x 10_*M b o r i c a c i d plus 0.6 percent calcium c h l o r i d e , or U/ no spray. !x£§£i§§rit._3_ The e f f e c t of a p p l y i n g a summer spray of st r o n t i u m was i n v e s t i g a t e d using a completely random design <CSD) of 9 r e p l i c a t i o n s and 4 treatments. I n d i v i d u a l t r e e s were sprayed with seven g a l l o n s of s o l u t i o n using a handgun sprayer. Sprays were a p p l i e d f i v e times at two weak i n t e r -v a l s commencing the f i r s t week i n J u l y . The treatments c o n s i s t e d o f : 4 1/ 0.6 percent calcium c h l o r i d e (77-80%) , 2/ 0,6 percent strontium c h l o r i d e (reagent g r a d e ) , 3/ 0.6 percent strontium c h l o r i d e plus 0.6 percent c a l c i u m c h l o r i d e , or 4/ no spray. Experiment 4 The r e l a t i v e e f f e c t i v e n e s s o f i n c r e a s i n g f r u i t c a l c i -um l e v e l s , m aintaining f l e s h f i r m n e s s , and reducing break-down by v a r i o u s methods of calcium a p p l i c a t i o n was examined i n two separate orchards. The two commercial orchards were s e l e c t e d on the bas i s of previous breakdown experience to g i v e one orchard of- moderate breakdown r i s k 32 and the second orchard, of high breakdown r i s k . Each i n d i -v i d u a l orchard was t r e a t e d as a separate experiment. A s i n g l e block of Spartan t r e e s of uniform age and growth h a b i t was s e l e c t e d i n each orchard and subsequently d i v i d e d i n t o a RCBD . Eight t r e e s i n each of f i v e b l o c k s were t r e a t e d i n d i v i d u a l l y with a t r e a t m e n t 4 c o n s i s t i n g o f : 1/ Four sprays of 0.6 percent commercial grade (77-80%) calcium c h l o r i d e a p p l i e d at two week i n t e r v a l s commencing J u l y 16, 1974. The sprays were a p p l i e d to i n d i -v i d u a l t r e e s at a r a t e of f i v e to ten g a l l o n s per t r e e by a commercial handgun sprayer, 2/ One spray of 2.0 or 4.0 percent calcium c h l o r i d e a p p l i e d two weeks before harvest. Due to the amount of l e a f burn from a 4.0 percent calcium c h l o r i d e spray , the owner of the high r i s k orchard permitted the use of the 2.0 percent spray only, k f o u r percent spray was a p p l i e d to the moderate r i s k orchard, 3/ One 4.0 percent c a l c i u m c h l o r i d e p o s t h a r v e s t d i p a p p l i e d immediately a f t e r h a r v e s t , 4/ A combination of the fo u r sprays of 0.6 percent calcium c h l o r i d e plus one spray two weeks before h a r v e s t at e i t h e r 2.0 or 4.0 percent, 5/ A combination of the fo u r sprays of 0.6 percent calcium c h l o r i d e p l u s the 4.0 percent postharvest d i p , 6/ A combination of the 2.0 or 4.0 percent p r e h a r v e s t spray plus the 4.0 percent postharvest d i p , 7/ A combination of f o u r sprays of 0.6 percant c a l c i -33 um c h l o r i d e , 2.0 percent calcium c h l o r i d e , 2.0 or 4.0 percent c a l c i u m c h l o r i d e preharvest spray, and the 4.0 percent p o s t h a r v e s t d i p , 8/ A c o n t r o l s e r i e s i n which no spray was a p p l i e d . lxp.9riment_5 D u p l i c a t e s e r i e s of one bushel samples were c o l l e c t e d from s i x t y - s i x commercial b i n l o t s at the time of shipment to the packinghouse. One s e r i e s was dipped immediately i n a s o l u t i o n of 4 percent commercial calcium c h l o r i d e and 0.05 percent s u r f a c t a n t . Both s e r i e s were placed i n 1.5 mil p e r f o r a t e d p o l y e t h y l e n e l i n e r s and s t o r e d at -0.6°C. The f r u i t was analyzed f o r firmness and breakdown at the c o n c l u s i o n of s i x months of common c o l d storage. iX2§£iment_6 Half f r u i t s of commercial maturity and of uniform s i z e were dipped i n a s o l u t i o n of 4.0 percent calcium c h l o r i d e plus 0.05 percent s u r f a c t a n t , l a b e l l e d with 10 uCi calcium-45 per ml. The dipped f r u i t were randomly d i v i d e d i n t o f o u r humidity s e r i e s with four removal dates of f o u r r e p l i c a t i o n s of f i v e apples each. The four storage h u m i d i t i e s c o n s i s t e d of ma i n t a i n i n g f o u r i n d i v i d u a l non-r e p l i c a t e d c a b i n e t s at 94% .RH, 87% RH, 80% SH, and 73% RH at -0.6°C. The- c a b i n e t s were not r e p l i c a t e d because of p r a c t i c a l l i m i t a t i o n s , but were l o c a l i z e d within a s i n g l e 34 storage room to maintain uniform storage c o n d i t i o n s . F i v e r e p l i c a t i o n s from each humidity chamber were removed a t 2, 4, 8, and 16 weeks a f t e r d i p p i n g . A c y l i n d e r of f r u i t .tissue was removed from each i n -d i v i d u a l apple using a No.9 cork borar. The sample was taken by i n s e r t i n g the borer i n t o the midsection of the non dipped h a l f of the f r u i t and t h r u s t i n g the borer through the f l e s h . The c y l i n d e r of apple f l a s h was removed from the borer by pushing the t i s s u e out through the top of the borer. The h a l f c y l i n d e r of t i s s u e from the dipped s i d e of the f r u i t was removed and s l i c e d i n t o s i x mm t h i c k apple d i s c s . F i v e apple d i s c s f o r each depth were c o l l e c t e d f o r each r e p l i c a t i o n and d r i e d to constant weight. The d i s c s were ashed f o r three hours at 5 75°C and taken up i n 3 ml of 0.5N HCL plus 16 ml of PCS L i g u i d S c i n t i l l a t i o n C o c k t a i l 5 . The prepared s c i n t i l l a t i o n samples were analyzed on a Beckman LCS-100 l i g u i d s c i n t i l l a t o r . 5Tradename of Amershara S e a r l e Co. 35 RESULTS The 2 percent lime sprays , a p p l i e d at the one-half i n c h green stage o f l e a f development f a i l e d to produce a s i g n i f i c a n t i n c r e a s e i n f r u i t calcium or r e d u c t i o n i n breakdown i n c i d e n c e i n the mature f r u i t of the three orchards (Table 1). A s i n g l e prebloom spray of e i t h e r 0.5, 1.5 or 2.5 percent CaCl2 (wt/wt) s i m i l a r l y f a i l e d to i n c r e a s e the mature f r u i t c alcium content or reduce break-down i n c i d e n c e (Table 2) i n comparison with c o n t r o l l e v e l s . Four summer sprays of calcium c h l o r i d e c o n t a i n i n g : 2.2 x 10-2, 2.2 x 10-3, or 2.2 x 10-* M b o r i c a c i d were not s i g n i f i c a n t l y b e t t e r than calcium c h l o r i d e alone i n i n c r e a s i n g the calcium content of f r u i t and redu c i n g breakdown. The a p p l i c a t i o n of fo u r summer calcium c h l o r i d e sprays s i g n i f i c a n t l y i n c r e a s e d f r u i t c a l c i um l a v e l s and decreased breakdown i n c i d e n c e (Table 3) . Five summer sprays of 0.6% (wt/wt) of s t r o n t i u m c h l o r i d e had no s i g n i f i c a n t e f f e c t on apple f i r m n e s s or 36 breakdown i n c i d e n c e when a p p l i e d alone or i n combination with a s i m i l a r calcium c h l o r i d e spray (Table 4) . F i v e sprays of 0,6% calcium or st r o n t i u m c h l o r i d e s i g n i f i c a n t l y reduced f r u i t f i r m n e s s at the c o n c l u s i o n of the storage p e r i o d , f i v e sprays of 0.6% calcium c h l o r i d e s i g n i f i c a n t l y reduced breakdown i n c i d e n c e when a p p l i e d alone or i n combination with strontium c h l o r i d e sprays (Table 4). SSE § Ei !l£Hi. _ £L Four sprays o f 0.6% calcium c h l o r i d e or a s i n g l e spray of 2% calcium c h l o r i d e s i g n i f i c a n t l y reduced break-down from 6 2 % i n the c o n t r o l s to 28.1% and 41.6% r e s p e c t i v e l y (Table 5 ) . The two methods of c a l c i u m a p p l i -c a t i o n were e g u a l l y e f f e c t i v e i n decreasing breakdown but n e i t h e r gave complete breakdown c o n t r o l . The 4% calcium c h l o r i d e postharvest dip and. a l l treatment combinations t h a t i n c l u d e d the dip were e g u a l l y e f f e c t i v e i n reducing breakdown t o a l e v e l not s i g n i f i c a n t l y d i f f e r e n t from zero. A l l c alcium c h l o r i d e a p p l i c a t i o n s s i g n i f i c a n t l y i n c r e a s e d f r u i t f l e s h c a l c ium l e v e l s except the two percent calcium c h l o r i d e a p p l i c a t i o n two weeks p r i o r to harvest. The treatments of f o u r sprays of 0.6%, four percent postharvest d ip or the combination of f o u r sprays p l u s a 2% p r e h a r v e s t spray p l u s the 4% calcium c h l o r i d e dip s i m i l a r l y i n c r e a s e d f r u i t calcium l e v e l s . The two 37 treatments of f o u r sprays p l u s a 4% d i p and the combination of a l l three methods were the most e f f e c t i v e i n r a i s i n g f r u i t calcium l e v e l s by 171 ppm over t h a t of the c o n t r o l s . Calcium-induced calyx end i n j u r y was not observed i n any of Orchard 1 samples (Table 5) . A l l c alcium a p p l i c a t i o n s s i g n i f i c a n t l y decreased breakdown i n c i d e n c e to zero i n Orchard 2, The calcium c h l o r i d e treatments were i n c r e a s i n g l y e f f e c t i v e i n r a i s i n g f r u i t f l e s h c a l c ium c o n c e n t r a t i o n s as calcium a p p l i c a t i o n s were combined. A combination of a l l three methods of c a l -cium a p p l i c a t i o n s i n c r e a s e d f r u i t c a l c i um to 537 ppm as compared to the c o n t r o l l e v e l of 242 ppm. Calyx end i n j u r y became s i g n i f i c a n t when f r u i t calcium l e v e l s reached 537 ppm. £x2eriment_5 The q u a d r a t i c r e g r e s s i o n e q u a t i o n , Dip Bd = 1.56 + 0.0075 C o n t r o l Bd + 0.0044 C o n t r o l Bd 2 (rz=0.58, F i q . 1) d e s c r i b e s the e f f e c t of a postharvest calcium c h l o r i d e d i p on breakdown development. The postharvest calcium c h l o r i d e dip reduced breakdown i n c i d e n c e f o r a l l i n d i v i d u a l samples but was unable to reduce c o n s i s t e n t l y the breakdown i n c i -dence below the commercial t o l e r a n c e of.5 percent f o r l o t s i n which breakdown i n untreated f r u i t exceeded 25%. Breakdown percentage i n dipped f r u i t was r e l a t e d t o 38 the average f r u i t weight (average apple s i z e ) by the eguation, Dip Bd = 57.72 - 1.079 Dip Wt + 0.0052 Dip Wt 2 ( r 2 = 0.56, F i g . 2) . The breakdown i n c i d e n c e i n c o n t r o l was s i m i l a r l y r e l a t e d to f r u i t s i z e by the l i n e a r eguation, C o n t r o l Bd = - 77.15 + 0.83 C o n t r o l Wt ( r 2 = 0.50, F i g . 4 ). The q u a d r a t i c r e g r e s s s i o n eguation d i d not give an i n c r e a s e i n the r 2 value i n p r e d i c t i n g c o n t r o l breakdown i n c i d e n c e from the apple weight over the l i n e a r r e g r e s s i o n eguation. Larger f r u i t s i z e s had a gr e a t e r breakdown i n c i -dence i n both the c o n t r o l and dip s e r i e s than d i d the s m a l l e r f r u i t s i z e s . The postharvest calcium c h l o r i d e d i p was l e s s e f f e c t i v e i n reducing breakdown i n c i d e n c e as the s i z e of the f r u i t t r e a t e d i n c r e a s e d ( F i g . 2). The post-h a r v e s t d ip treatment reduced breakdown i n c i d e n c e over the e n t i r e range of apple weights. The e f f e c t of a fo u r percent dip i n maintaining f r u i t firmness i s estimated by the c a l c u l a t e d l i n e , Dip Press = 1.70 + 0.64 C o n t r o l Press ( r 2 = 0.48, F i g , 3) . The average f r u i t firmness values f o r the dipped and c o n t r o l f r u i t were an i d e n t i c a l 4.7 kg when measured a f t e r storage. The pos t h a r v e s t calcium c h l o r i d e dip d i d not prevent f r u i t s o f t e n i n g i n storage. 39 Ra d i o a c t i v e calcium moved s t e a d i l y i n t o the f r u i t f l e s h i n c o l d s t o r a g e (Table 7 ) . Two weeks a f t e r the d i p , s i g n i f i c a n t l e v e l s of calcium-45 were d e t e c t a b l e i n the 0 to 6 mm depth below the s k i n (Table 6). At l a t e r removals, the calcium-45 was detected near the core. A f t e r e i g h t weeks of st o r a g e , s i g n i f i c a n t l e v e l s of calcium-45 were d e t e c t a b l e i n the t i s s u e immediately surrounding the core (Table 6). Calcium-45 l e v e l s showed p r o g r e s s i v e accumula-t i o n s w i t h i n the f l e s h with i n c r e a s e d time i n stor a g e . A storage humidity of 94% RH s i g n i f i c a n t l y lowered the r a t e of calcium-45 p e n e t r a t i o n i n t o the 0 to 6 mm depth of the apple t i s s u e compared to that found at the lower storage h u m i d i t i e s (Table 7) .. At the c o n c l u s i o n of s i x t e e n weeks of storage, the p e n e t r a t i o n of calcium-45 i n t o the 0 to 6 mm depths under 94% RH was egual to that found at 80% RH and 73% RH. The p e n e t r a t i o n of calcium-45 i n t o the 0 to 6 mm depth f o r the 87% RH was s i g n i f i c a n t l y h igher than f o r the 94% RH at a l l removal dates. A l l calcium-45 c o n c e n t r a t i o n s at f r u i t depths g r e a t e r than 6mm were u n a f f e c t e d by storage humidity at the c o n c l u s i o n of f o u r weeks of storage. A f t e r e i g h t and s i x t e e n weeks of storage the 6-12 mm f l e s h depth had s i g -n i f i c a n t l y l e s s calcium at 94% BH than at the remaining h u m i d i t i e s . At the c o n c l u s i o n of fo u r months of s t o r a g e , the calcium-45 c o n c e n t r a t i o n of the 6 to 12 mm depths i n the 94% RH was not s i g n i f i c a n t l y d i f f e r e n t than t h a t a t 40 7 3 % RH b u t r e m a i n e d s i g n i f i c a n t l y d i f f e r e n t t h a n t h o s e a t 8 7 % and 8 0 % RH. 41 DISCUSSION Supplementing f r u i t calcium l e v e l s by calcium s p r a y s a p p l i e d p r i o r to f r u i t formation proved u n s u c c e s s f u l . The prebloora lime and calcium c h l o r i d e spray treatments were unable t o supply s u f f i c i e n t l e v e l s of calcium to overcome the l e a f demand f o r calcium and r a i s e f r u i t c a l c i um l e v e l s . I n c r e a s e s i n f r u i t c alcium l e v e l s would be r e f l e c t e d by decreased breakdown i n c i d e n c e s , however breakdown was u n a f f e c t e d by the prebloom calcium sprays. Dormant o i l , c a s e i n , soya f l o u r or B i o f i l m 3 were i n c l u d e d with the lime sprays as ' s t i c k e r s ' t o leav e a g r e a t e r volume of lime t o the t r e e . V i s u a l assessments of the amount of lime remaining on the t r e e , one week a f t e r spray, i n d i c a t e d that c a s e i n and soya f l o u r were s u p e r i o r i n adhering lime onto the t r e e . However, the lime t r e a t -ments using soya f l o u r or c a s e i n were as i n e f f e c t u a l i n r a i s i n g f r u i t c a l c i um as the two percent lime spray a l o n e . Any r e s e r v o i r of calcium c r e a t e d i n the t r e e t i s s u e s ( f r u i t spurs included) which i s able to move i n t o the developing f r u i t l e t i s s u b j e c t to competition from the r a p i d l y m e t a b o l i z i n g l e a v e s . Immature l e a v e s with a,high metabolic a c t i v i t y and t r a n s p i r a t i o n a l l o s s impose a gr e a t e r demand on the t r e e calcium s u p p l i e s than the developing f r u i t l e t s (Faust and Shear 1971). 42 R e d i s t r i b u t i o n of calcium w i t h i n the l e a f , t r e e and f r u i t e q u i l i b r i u m i s determined by the l e a f / f r u i t r a t i o of c a l -cium content(Van Goor and Wiersma 1974) and i s u n f a v o r a b l e to calcium accumulation by the immature f r u i t l e t . The l e a f c a l c i um demand must be s a t u r a t e d before calcium i s a v a i l a b l e f o r f r u i t uptake. Ex29riraent_2 F r u i t calcium l e v e l s were c o n s i s t e n t l y i n c r e a s e d and breakdown i n c i d e n c e was decreased by midsummer calcium c h l o r i d e sprays (Table 4,5). These r e s u l t s agree with the r e p o r t s of Mason (1971). The i n c l u s i o n of boron as s o l u b l e b o r i c a c i d with the calcium c h l o r i d e sprays f a i l e d to have a s i g n i f i c a n t e f f e c t on the f r u i t c a l c i um content or breakdown i n c i d e n c e . These r e s u l t s are i n c o n t r a s t to the p o s i t i v e e f f e c t of i n c l u d i n g boron i n n u t r i e n t s o l u t i o n s on apple s e e d l i n g calcium l e v e l s (Woodbridge et a l . 1974). Faust and Shear (1968) d e s c r i b e d boron as being b e n e f i c i a l to calcium movement with i n the apple t r e e . Shear and Faust (1971) found that f o u r sprays of 1.6 x 10 _ 3M b o r i c a c i d i n c r e a s e d the c a l c i u m content of midshoot and b a s a l l e a v e s at varying l e v e l s of c a l c i u m supply. The r e s u l t s r e p o r t e d here i n d i c a t e t h a t b o r i c a c i d a p p l i e d at c o n c e n t r a t i o n s as high as 2.2 x 10~ 2M d i d not f a c i l i t a t e c a l c i um r e t e n t i o n by apple f r u i t . As l e a f c a l c ium determinations were not done, i t i s p o s s i b l e that the i n c l u s i o n of boron with the 43 f o u r c a l c i u m sprays may have s y n e r g i s t i c a l l y i n c r e a s e d l e a f calcium l e v e l s . Increased l e v e l s of boron may d i s p l a c e calcium i o n s adsorbed to the t r a n s p o r t s i t e s and r e l e a s e these ions f o r t r a n s l o c a t i o n to the t r a e l e a v e s and f r u i t . However, the a d d i t i o n of boron to the t r e e may a f f e c t the xylem calcium movement to the l e a v e s and may be i n e f f e c t u a l on the phloem calcium t r a n s p o r t to the f r u i t . Experiment_3 W i l l s et a l . (1975) determined that s t r o n t i u m i n j e c t e d i n t o the core c a v i t y of s e v e r a l apple c u l t i v a r s c o u l d reduce breakdown i n c i d e n c e . A three spray program of 0.8 percent s t r o n t i u m was found to have an e f f e c t egual to a s i m i l a r calcium spray program i n reducing the i n c i d e n c e of senescent breakdown and b i t t e r p i t i n D e l i c i o u s apples ( W i l l s et a l . 1975). The r e s u l t s presented show t h a t strontium had no e f f e c t on breakdown i n c i d e n c e when a p p l i e d as f i v e 0.6 percent (anhydrous reagent grade stro n t i u m c h l o r i d e ) midsummer sprays. Combining an egual amount of s t r o n t i u m c h l o r i d e with calcium c h l o r i d e using a f i v e - s p r a y program d i d not change the breakdown i n c i d e n c e from that•expected from the a p p l i c a t i o n of calcium alone. Hurd-Karrer (1939) and da S i l v a (1954) found t h a t strontium was a n t a g o n i s t i c to the p h y s i o l o g i c a l a c t i o n of calcium i n wheat and maize r e s p e c t i v e l y and r e s u l t e d i n p l a n t i n j u r y . Although strontium has very s i m i l a r chemical p r o p e r t i e s to c a l c i u m , i t i s u n l i k e l y to r e p l a c e the f u n c t i o n of calcium i n maintaining c e l l u l a r i n t e g r i t y and reducing breakdown i n c i d e n c e . As strontium d i d not i n f l u e n c e breakdown from the c o n t r o l , i t i s u n l i k e l y t h a t the strontium i o n s r e p l a c e d the c a l c i u m adsorbed to the c e l l u l a r membranes. Strontium a l s o i s not able t o a c t i n the same p h y s i o l o g i c a l r o l e as calcium i n p r e v e n t i n g breakdown development when a p p l i e d by a summer spray program. F u r t h e r r e s e a r c h may use strontium c h l o r i d e p o s t h a r v e s t d i p s with a t h i c k e n e r (Kelzan 6) to study strontium i n h i b i t i o n of c a l c i u m uptake and p h y s i o l o g i c a l f u n c t i o n . As pos t h a r v e s t d i p s are e f f i c i e n t i n r a i s i n g f r u i t c a l c i um l e v e l s , the technique may a l s o i n c r e a s e the amount of stro n t i u m taken up by the f r u i t t i s s u e s . The p o s s i b i l i t y remains t h a t a g r e a t e r c o n c e n t r a t i o n of strontium i n the f r u i t t i s s u e s may c o m p e t i t i v e l y i n h i b i t the a c t i o n of c a l c i u m although the strontium a p p l i e d i n summer sprays d i d not. A l l summer spray treatments s i g n i f i c a n t l y reduced apple firmness at the c o n c l u s i o n of three months of common c o l d storage (Table 4). However, Mason et a l . (1974, 1975) found postharvest calcium d i p s t o maintain apple f i r m n e s s i n storage f o r the Spartan and Mcintosh c u l t i v a r s . The e f f e c t of ca l c i u m a p p l i c a t i o n s i n maintaining f r u i t f i r m -ness i s h i g h l y c o n t r o v e r s i a l and v a r i a b l e . In our 6Tradename of Kelco Co. San Diego 45 l a b o r a t o r i e s we have been unable to show c o n s i s t e n t l y h i g h e r f r u i t f i r m n e s s r e s u l t i n g from any calcium a p p l i c a -t i o n i n f o u r years of t e s t s . lxp_eriment_4 The p o s i t i v e e f f e c t of c a l c i u m sprays i n i n c r e a s i n g f r u i t c alcium and r e d u c i n g breakdown i n c i d e n c e appears to r e q u i r e d i r e c t c o n t a c t with the f r u i t (prebloom s p r a y s d i d not a f f e c t f r u i t calcium c o n t e n t ) . Mason (1971) suggested t h a t c a l c i u m sprays a p p l i e d l a t e r i n the growing season were more e f f e c t i v e i n r a i s i n g f r u i t calcium l e v e l s , and that a 4 percent postharvest d i p was even more e f f e c t i v e i n r a i s i n g f r u i t calcium l e v e l s than summer spray programs (Mason 1971). Some summer spray programs were as e f f e c t i v e as post-harvest d i p s i n r a i s i n g f r u i t calcium l e v e l s (Table 5). Combinations of two or more of the calcium a p p l i c a t i o n methods appeared to be a d d i t i v e i n i n c r e a s i n g f r u i t c a l c i -um l e v e l s . fi. s i n g l e preharvest spray of 2 percent calcium appeared to be i n s u f f i c i e n t t o i n c r e a s e f r u i t c a l c i um above the c o n t r o l l e v e l . The s i n g l e preharvest spray r e s u l t e d i n n o t i c e a b l e marginal l e a f burn which was d i r e c t l y r e l a t e d to the con-c e n t r a t i o n of c a l c i u m c h l o r i d e . The l e a f burn appears as brown n e c r o t i c t i s s u e and may encompass the e n t i r e l e a f a t spray c o n c e n t r a t i o n s of 5 percent calcium c h l o r i d e . Dewey 46 (1972) noted that the preharvest spray may i n c r e a s e f r u i t c a l c i u m l e v e l s by d i r e c t f r u i t c o n t a c t and removal of the l e a f demand f o r calcium supply. Permanent t r e e damage has not been observed f o r any c a l c i u m c h l o r i d e spray up t o 5 percent, although a heavy f r u i t drop was experienced i n one year's r e s u l t s (N. Looney, personal communication). Continued use of preharvest calcium sprays may i n c r e a s e the calcium l e v e l s i n f o l l o w i n g crop y e a r s . The high breakdown i n c i d e n c e i n Orchard 1 as a r e s u l t of low f r u i t c alcium (Table 5 ) , was not s a t i s f a c t o r i l y c o n t r o l l e d by the calcium spray a p p l i c a t i o n s . & post-harvest d ip or a d d i t i o n a l calcium treatments were r e g u i r e d to give adequate breakdown c o n t r o l . Any calcium a p p l i c a -t i o n to orchards with a low breakdown i n c i d e n c e (Orchard 2, Table 5) may be s u f f i c i e n t to c o n t r o l breakdown. I n c r e a s i n g f r u i t c a l c i um l e v e l s by sprays or d i p s , may prevent the development of breakdown by d e c r e a s i n g the age dependent s o l u b i l i z a t i o n of calcium adsorbed t o the c e l l membrane b i n d i n g s i t e s . R a i s i n g the s o l u b l e c a l c i u m content w i t h i n the apple f r u i t would l e s s e n the c o n c e n t r a t i o n g r a d i e n t s t r e s s placed on the membrane bound calcium. The calcium i n f u s e d i n t o the apple f r u i t may a l s o become adsorbed to the membrane b i n d i n g s i t e s vacated when the calcium i s s o l u b i l i z e d through aging. The o v e r a l l e f f e c t of i n c r e a s e d f r u i t c alcium l e v e l s i s to maintain the d i f f e r e n t i a l p e r m e a b i l i t y c h a r a c t e r i s t i c s of the c e l l u l a r membranes and c e l l u l a r compartmentalization. Ul The occurrence of c a l y x end i n j u r y which manifested i t s e l f as c r a c k i n g of the s k i n and subseguent d e s i c c a t i o n of the f l e s h became s i g n i f i c a n t when f r u i t calcium l e v e l s were r a i s e d t o approximately 537 ppm. These r e s u l t s suggest t h a t an optimum f r u i t calcium l e v e l e x i s t s which minimizes the l o s s e s due to breakdown and the l o s s e s due to c a l y x end i n j u r y . Optimum f r u i t c alcium l e v e l s should be w i t h i n the range of approximately 300 to 500 ppm. In p r a c t i s e , any orchard with calcium l e v e l s w i t h i n the optimum range need not have any calcium a p p l i e d . F r u i t c alcium f a l l i n g below the 300 ppm minimum may r e q u i r e c a l -cium a p p l i c a t i o n s s u f f i c i e n t t o r a i s e the f r u i t c a l c i um l e v e l to one w i t h i n the optimum range. l i d s t e r e t a l . (1975) have demonstrated t h a t l a r g e f r u i t s r e q u i r e g r e a t e r endogenous calcium c o n c e n t r a t i o n s than do s m a l l e r f r u i t s to prevent breakdown. Large f r u i t may t h e r e f o r e r e q u i r e more than the 300 ppm f l e s h c a l c i u m to assure minimum breakdown l e v e l s . The 4 percent calcium c h l o r i d e d i p was e f f e c t i v e i n reducing breakdown i n c i d e n c e over the range of f r u i t s i z e s s t u d i e d . However, the post-harvest d i p was more e f f i c i e n t i n reducing breakdown i n f r u i t s i z e s of approximately 150 to 200 grams ( F i g . 1). F r u i t s i z e s below 125 grams have high l e v e l s of f r u i t c a l -cium and do not show a tendency to breakdown. Dipping 48 sm a l l apples gave l i t t l e decrease i n breakdown l e v e l s s i n c e the l a t t e r were a l r e a d y low. Dipping f r u i t i n calcium c h l o r i d e shows the p o t e n t i a l of reducing breakdown over a wide range of s u s c e p t i b i l i t y ( F i g . 2). T h i s procedure however, was unable to reduce c o n s i s t e n t l y c o n t r o l breakdown i n c i d e n c e s to zero but reduced breakdown to a l e v e l below the 5 percent commer-c i a l maximum when c o n t r o l l e v e l s of breakdown were 25 percent or l e s s . Dewey (1972) observed a s i m i l a r p a t t e r n of breakdown r e d u c t i o n with a 4 percent calcium c h l o r i d e d i p . A s i m i l a r study could be used to study the e f f e c t of a postharvest calcium c h l o r i d e d i p with K e l z a n 6 t h i c k e n e r added. As a thi c k e n e d c a l c i u m c h l o r i d e d i p s o l u t i o n shows a p o t e n t i a l of i n f u s i n g a g r e a t e r amount of calcium i n t o the apple f l e s h than a non-thickened s o l u t i o n , i t i s reasonable to assume a thi c k e n e d s o l u t i o n would provide b e t t e r breakdown c o n t r o l . Mason et a l . (1974, 1975) determined that 4 percent calcium c h l o r i d e d i p s were more e f f e c t i v e i n r a i s i n g f r u i t c a l c i u m l e v e l s and reducing breakdown when a p p l i e d without a s u r f a c t a n t or with a t h i c k e n e r . Dewey (1972) found the a d d i t i o n of a s u r f a c t a n t to the d i p d i d not a f f e c t break-down c o n t r o l . I t i s l i k e l y t h a t the curve i n F i g u r e 2 would s h i f t to provide g r e a t e r breakdown c o n t r o l at a l l l e v e l s of i n c i d e n c e i f 0.25% K e l z a n 6 were i n c l u d e d i n the dip s o l u t i o n (Mason 1974). The a d d i t i o n of a t h i c k e n e r to 49 a d i p serves to adhere a g r e a t e r q u a n t i t y of dip s o l u t i o n to the s u r f a c e of the apple and c r e a t e a l a r g e r e s e r v o i r of calcium f o r p e n e t r a t i o n i n t o the apple f l e s h (B. Drought, personal communication). The postharvest dip had no e f f e c t on f r u i t firmness a f t e r s i x months of c o l d s t o r a g e . The average f r u i t firmness f o r 66 p a i r e d samples of c o n t r o l and dipped f r u i t were i d e n t i c a l (4.7 kg). The e f f e c t of the p o s t h a r v e s t d i p expressed as a r e g r e s s i o n equation appeared i n F i g u r e 3. The r e g r e s s i o n l i n e of f i r m n e s s of dipped f r u i t p l o t t e d a g a i n s t the f i r m n e s s of undipped f r u i t 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 45° median over the e n t i r e range of f r u i t f i r m n e s s . These r e s u l t s are i n c o n f l i c t with those of Dewey (1972) and Mason (1975) which i n d i c a t e t h a t a 4 percent calcium c h l o r i d e d i p maintains f l e s h firmness i n s t o r a g e . Bramlage et a l . (1974) found t h a t f r u i t with high l e v e l s of p e e l calcium had lower f r u i t f i r m n e s s than f r u i t with low p e e l c a l c i u m , at the c o n c l u s i o n of f i v e months of common c o l d s t o r a g e . The author b e l i e v e s the e f f e c t of high f l e s h calcium l e v e l s i n m a i n t a i n i n g f r u i t f i rmness i s h i g h l y v a r i a b l e and u n r e l i a b l e . Orchard and y e a r l y v a r i a t i o n s appear to be very prominent i n i n f l u e n c i n g the c a l c i u m - f r u i t firmness r e l a t i o n s h i p . 50 Calcium-45 a p p l i e d i n a postharvest dip moved s t e a d i l y and p r o g r e s s i v e l y i n t o the f r u i t f l e s h with time i n storage (Table 6). M i l l i k a n and Hangar (1965) found s i m i l a r p e n e t r a t i o n of calcium-45 through the apple s k i n and f l e s h of Granny Smith apple f r u i t s . Hieneke and Benson (1966) d i d not f i n d calcium-45 to penetrate the s k i n of mature Jonathan f r u i t when a p p l i e d as 1 percent calcium c h l o r i d e p o s t h a r v e s t d i p . Mason (1975) using an u n l a b e l l e d 4 percent calcium c h l o r i d e p o s t h a r v e s t dip found s i g n i f i -cant i n c r e a s e s i n Spartan f l e s h calcium l e v e l s . The i n c r e a s e s i n f l e s h calcium content observed by Mason were higher at a l l f l e s h depths and sampling dates than observed i n the present experiment. However, i n h i s experiment Mason (1975) d i d not use a s u r f a c t a n t i n the postharvest dip which may have i n c r e a s e d the amount of calcium dip r e t e n t i o n on the apple s u r f a c e and the subsequent p e n e t r a t i o n i n t o the f r u i t . Calcium appeared to penetrate r a p i d l y i n t o the f l e s h immediately beneath the apple s k i n w i t h i n two weeks of the d i p . At subseguent sampling dates calcium accumulated at a slower r a t e i n the 0-6 mm depth of the t i s s u e . The c a l c i -um-45 i n i t i a l l y l o c a t e d i n the 0-6 mm depth a p p a r e n t l y moved f u r t h e r i n t o the f l e s h with continued time i n s t o -rage. High storage r e l a t i v e humidity (94% RH) s i g n i f i c a n t l y r e s t r i c t e d the r a t e of c a l c i u m p e n e t r a t i o n i n t o the apple 51 f l e s h (Table 7). At 94% RH, l i q u i d droplets ware v i s i b l e on the f r u i t . The surface water presumably dissolved the calcium on the surface of the f r u i t and e f f e c t i v e l y diluted the external calcium concentration. Diluting the external calcium concentration would decrease the concentration gradient within the apple f l e s h and may explain reduced penetration rates at 94% RH. The ef f e c t of high humidity i n r e s t r i c t i n g calcium-45 movement observed by Van Goor (1973) at 20 - 30 °C i 3 s i m i l a r to that observed i n the present experiment under storage conditions of -0.6°C. The optimum storage humidity for calcium penetration from a postharvest dip approximates 87% RH and where storage humidity approached 80% RH or 75% RH the speed of calcium-45 uptake declined. Storage r e l a t i v e humidity affected the rate of calcium-45 penetra-tion markedly in the early storage l i f e . The e f f e c t of storage humidity on calcium uptake became less s i g n i f i c a n t with continued time i n storage. Wilkinson (1965) suggested that f r u i t stored i n high humidity had a greater permeability to gas d i f f u s i o n with increased storage time. This e f f e c t of high humidity may account for the acceleration of calcium uptake by apple f r u i t , r e l a t i v e 87% RH, with prolonged storage time. Alternatively, the calcium accumulation by the f r u i t , i n storage, may reach an upper l i m i t . The f r u i t stored i n the 94% RH may take longer to reach the same calcium concentrations than do f r u i t stored i n 87% RH. 52 Future research may e luc idate the e f fect of storage humidity on the uptake of calcium when applied with a thickener. Mason (1974) has shown greater calcium uptake by the f r u i t when 0.25 % Kelzan 6 i s added to the dipping so lu t ion . It would be of commercial importance to i den t i f y the storage humidity reguired to give the most rapid uptake of of calcium from a thickened calcium ch lor ide dipping so lu t ion . 53 SUMMARY 1. The a p p l i c a t i o n of 2 percent lime sprays plus s t i c k e r s and a s i n g l e c a l cium c h l o r i d e spray one t o two weeks before bloom d i d not s i g n i f i c a n t l y a f f e c t mature f r u i t storage calcium l e v e l s or breakdown i n c i d e n c e i n st o r a g e . 2. The a p p l i c a t i o n of low l e v e l s of boron along with f o u r midsummer calcium c h l o r i d e sprays d i d not s i g n i f i c a n t l y i n c r e a s e c alcium uptake from the sprays or reduce break-down i n c i d e n c e over that expected from the ca l c i u m sprays alone. 3. The a p p l i c a t i o n of f i v e midsummer sprays of st r o n t i u m c h l o r i d e f a i l e d t o have a s i g n i f i c a n t e f f e c t on f r u i t breakdown i n c i d e n c e . The a p p l i c a t i o n of f i v e summer sprays of calcium c h l o r i d e reduced breakdown i n c i d e n c e . A l l spray treatments reduced f r u i t firmness from the c o n t r o l l e v e l s . 4. Calcium c h l o r i d e sprays i n c r e a s e d f r u i t c alcium l e v e l s comparable to a 4 percent calcium c h l o r i d e p o s t h a r v e s t d i p . Calcium sprays f a i l e d to reduce breakdown to the same l e v e l as d i d the 4 percent p o s t h a r v e s t d ip or any combination of calcium spray a p p l i c a t i o n s i n a high break-down r i s k orchard. Any ca l c i u m a p p l i c a t i o n t o the low breakdown r i s k orchard s i g n i f i c a n t l y reduced breakdown i n -cidence to zero. Calyx end i n j u r y caused by ca l c i u m c h l o r i d e became s i g n i f i c a n t when s u f f i c i e n t calcium c h l o r i d e was a p p l i e d to produce f l e s h calcium l e v e l s over 500 ppm. 54 5. A 4 percent calcium c h l o r i d e postharvest d i p reduced breakdown i n c i d e n c e over a range of apple f r u i t s i z e s and breakdown p o t e n t i a l s . The p o s t h a r v e s t dip d i d not e f f e c t f r u i t f i r m n e s s i n storage. 6. High and low storage h u m i d i t i e s (94% RH, 80% RH to 73% RH) r e s t r i c t e d calcium-45 movement i n t o the appla f l e s h i n the storage p e r i o d . Moderate storage h u m i d i t i e s (87% RH) in c r e a s e d the i n i t i a l r a t e of ca l c i u m p e n e t r a t i o n . D i f f e r e n c e s i n the f l e s h calcium accumulation at the d i f f e r e n t s torage h u m i d i t i e s decreased with s t o r a g e time. Low f r u i t c alcium l e v e l s have been c l o s e l y l i n k e d to the development of Spartan breakdown. I n c r e a s i n g the endogenous f l e s h calcium l e v e l s by sprays or p o s t h a r v e s t d i p s are commercial s o l u t i o n s to maximizing market confidence In the produce. Orchards which do not show a high p o t e n t i a l f o r breakdown may only r e q u i r e a s i n g l e c a l c i u m spray program to reduce the breakdown p o t e n t i a l to zero. Orchards with a high breakdown i n c i d e n c e may r e q u i r e both a ca l c i u m spray and d i p program to i n s u r e zero breakdown i n c i d e n c e a f t e r a commercial storage p e r i o d . The r e s u l t s presented i n d i c a t e that c a l c i u m d i p s or s p r a y s are unable to maintain f l e s h firmness i n storage. A commercial d i p p i n g program to improve the f l e s h firmness of Spartan f r u i t a f t e r s t o r a g e , would be uneconomical. The Okanagan f r u i t i n d u s t r y should continue the present p o s t h a r v e s t calcium c h l o r i d e dipping program. F r u i t which have been dipped i n calcium should be s t o r e d 55 i n 87% RH to i n s u r e calcium p e n e t r a t i o n e a r l y i n the storage p e r i o d . T h i s would provide p r o t e c t i o n from breakdown development i n f r u i t packed and shipped soon a f t e r h a r v e s t . Supplementing f r u i t calcium l e v e l s does not appear harmful u n t i l f r u i t c a l c i u m l e v e l s exceed 500 ppm. An i n d u s t r y program should be designed to maintain Spartan f r u i t c alcium l e v e l s i n the optimum range of 300 to 500 ppm. 56 LITERATURE CITED ABBOTT, D.L. 1970. The r e l a t i o n s h i p between v e g e t a t i v e g r r o w t h and f r u i t s e t i n the ap p l e . P r o c i _ 1 8 t h _ I n t J _ _ H o r t i £2Q2_ 1:57. ANDERSON, A.J. and W.A. JACKSON. 1972. I n f l u e n c e of n i -t r o g e n s u p p l y on uptake and t r a n s l o c a t i o n o f s t r o n t i u m and c a l c i u m i n wheat s e e d l i n g s . P l a n t _ P h y s i o l i 26:175-181. ANON. 1971. Breakdown i n c o n t r o l l e d atmosphere s t o r a g e . S p a r t a n ' s v e r s u s c a l c i u m . B__C, T r e e _ _ F r u i t s _ R e _ o r t : 10 pp. BANGERTH, F. 1973. 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E f f e c t o f p r e b l o o m l i m e s p r a y s on f r u i t c a l c i u m and b r e a k d o w n i n c i d e n c e * O r c h a r d 1 O r c h a r d 2 O r c h a r d 3 T r e a t m e n t F l e s h C a l c i u m (ppm) B r e a k -down (%) F l e s h Culzium (ppm) B r e a k -down (%) F l e s h Ca l c i u m ' (ppm) B r e a k -down (%) C o n t r o l 274a 78.6a 290a 73. 5a 308a 40.4a 2% C a ( O H ) 2 281a 41 .6a 274a 74.2a 29 2 a 38.6a 0. 1% o i l + 2% Ca (OH) 2 308a 57. 1a 297a 54.1a 273a 49.0a 0.2% o i l + 2% Ca (OH) 2 304a 42.8a 272a 80. 2a 267a 55.4a 0.1% c a s e i n + 2% Ca(OH)2 285a 55 . 9a 278a 76.7a 315a 27. 9a 0.1% s o y a f l o u r + 2% Ca (OH) 2 313a 49. 9a 277a 7 4. 9a 264a 50. 8a 0.05% B i o - F i l m + 2% Ca(OH)2 275a 54 .0a 287a 6 0.1a 247a 69.5a 4% Lime s u l f u r 3 06a 6 4.6a Mean s e p a r a t i o n , f o r a s i n g l e o r c h a r d , by Newman-Keuls t e s t , 5% l e v e l . 84 Table 2, Breakdown versus s i l v e r t i p calcium c h l o r i d e sprays. Treatment F r u i t c a l c ium (ppm dry wt.) Break-down (%) Check 211ab 94.0a 0.5% CaCl2 spray 224a 84.2a 1.5% CaCl2 spray 192b 79.3a 2.5% CaCl2 spray 2 33a 85.9a Mean s e p a r a t i o n by Newman-Keuls t e s t , 5% l e v e l . 85 Table 3. Effect of summer calcium plus boron sprays on f r u i t calcium levels and breakdown incidence. Spray Treatment C o n t r o l 0.6% c a l c i u m c h l o r i d e 0.6% CaC12 p l u s 2.2x10-2M B o r i c a c i d 0.6% CaCl2 p l u s 2.2x10-3M B o r i c a c i d 0.6% CaCl2 p l u s 2.2x10~*M B o r i c a c i d F l e s h c a l c i u m (ppm d r y wt) 23 6b 301a 333a 320a 310a Breakdown (%) 41. 8a 14.4b 8.9b 14. 8b 14. 9b Mean s e p a r a t i o n by Newman-Keuls t e s t , 5% l e v e l . 86 T a b l e 4. E f f e c t of midsummer c a l c i u m and s t r o n t i u m s p r a y s on Sp a r t a n a p p l e f i r m n e s s and breakdown. Treatment F r u i t f i r m n e s s (*g) Break-down («) C o n t r o l 5. 4a 28.7a 0.6% CaCl2 5.0b 13. 2b 0.6% S r C l 2 5.1b 30.3a 0.6% CaCl2 p l u s 0.6% S r C l 2 5.0b 13.4b Mean s e p a r a t i o n by Newman-Keuls t e s t , 5% l e v e l . T a b l e 5. P e r c e n t b r e a k d o w n and f r u i t c a l c i u m c o n t e n t v e r s u s c a l c i u m c h l o r i d e a p p l i c a t i o n . T r e a t m e n t P e r c e n t O r c h . #1 b r e a k d o w n O r c h . #2 F r u i t c a l c coa t e n t (ppm d r y v Orzh. If1 i u m e i g h t ) . Orch #2 C a l y x i n j u r y (%) O r c h #1 O r c h #2 C o n t r o l . No c a l c i u m a p p l i e d . 6 2 . O a 2 39.1a 213d 242d 0.0a 0.0b '4 s p r a y s o f 0.6% CaC12 28. 1b 2. 3b 279bc 327c 0. 0a 0.0b 1 s p r a y 1 o f CaC12 41.6b 3. 9b 251cd 316c 0.0a 0.0b 1 4% C a C l 2 d i p 9. 4c 0. 7b 293bc 365c 0. 0a 3. Oab 4 s p r a y s o f 0.6% p l u s 1 s p r a y 1 o f C a C l 2 1 2.9c 0. 6b 305bc 4 19b 0. Oa 0.0b 4 s p r a y s o f 0.6% CaC12, 4% C a C l 2 d i p 1 . 4c 0. 0b 384a U54b 0. 0a 3.2ab 1 s p r a y 1 C a C l 2 p l u s 4% C a C l 2 d i p 5.3c 0. 0b 326b 453b 0.0a 2 . 4b 4 s p r a y s o f 0.6% C a C l 2 p l u s 1 s p r a y 1 CaC12 C a C l 2 p l u s 4% C a C l 2 d i p 0.0c 0. 0b 385a 5 3 7a 0.0a 6. 5a O r c h a r d No. 1 - 2% CaC12 s p r a y O r c h a r d No. 2 - 4% C a C l 2 s p r a y 2 M e a n s e p a r a t i o n , f o r a s i n g l e o r c h a r d , by Newman-Keuls t e s t , 5% l e v e l . 88 T a b l e 6. E f f e c t o f s t o r a g e t i m e on c a l c i u m u p t a k e . D u r a t i o n o f I n c r e a s e i n f r u i t c a l c i u m c o n t e n t (ppm) s t o r a g e D epth o f f r u i t t i s s u e (wk) 0-6mm 6-12mm 12-18mm 18-24mm 24-30mm 2 37. 0a 1.8e 0.2e 0. 1e 1.1e 4 47.8b 6.4f 0.6e 0.5e 1.6e 8 61.9c 24.8g 7 .1f 4.8f 9.Of 16 69.3d 36.8a 21.4g 15.7g 17.1g Mean s e p a r a t i o n by Newman-Keuls t e s t , 5% l e v e l . 89 Table 7. E f f e c t of storage humidity on the r a t e of calcium p e n e t r a t i o n i n Spartan apples. Increas e i n f r u i t c alcium conte nt(ppm) Storage Depth f rom epid ermis (mm) . Humidity 0-6 6-12 12-18 18-24 24-30 2 weeks a f t e r d i p 94% 23. 1a 1. 2b 0.1b 0.1b 3.6b 87% 56.9c 3.1b 0.2 b 0.2 b 0.4b 80% 37. 1d 1. 9b 0.2b 0. 1b 0.3b 73% 31. Od 1.3b 0.2 b 1 0. 1b 0. 1b 1 month a f t e r d ip 94% 38.1a'> 5. 3b 0.5b 0. 9b 3. 9b 87% 59. 9d 9.4b 0.7b 0. 5b 0.5 b 80% 49. 4c 5.3b 0.7 b 0.5b 1.3b 73% 43.7c 5.6 b 0.5b 0. 2b 0. 6b 2 months a f t e r d i p 94% 42,7a 12.8b 4.3b 6.8b 15.3b 87% 77. 5c 30.2d 9.1b 6. 3b 11.0b 80% 59. 2e 28. 1d 8.2b 2.9b 3.5b 73% 68.3ce 28.3d 6.7 b 3. 1b 6.2b 4 months a f t e r d i p 94% 63. 6a 29. 8e 21.9c 12. 5c 15.4c 87% 76.3d 43. 1b 25.0bc 18.7c 18.2c 80% 72.7ad 41.4b 22.9c 16.3c 16. 0c 73% 64.Sad 32.9be 20.9c 15. 4c 19.0c Mean s e p a r a t i o n , f o r a s i n g l e removal l e v e l . date, by Neuman-Keuls t e s t , 5% 90 75 + + .... + ....+....•+....•••....+..... + .... + , 60 1 1 1 1 45 30 15 0 + 2*T" 1 1 1 2 .+....+. +....+....+....+....+....+....+....+., 10 30 50 70 y0 20 40 60 80 100 Co n t r o l Breakdown (pet) f i g . 1. Scattergram of percentage breakdown i n f r u i t clipped i n calcium c h l o r i d e versus c o n t r o l . Dip Bd = 1.56 + 0.0075 C o n t r o l Bd + 0.0044 C o n t r o l Bd2 (r2 = 0.58) 91 75 + 60 45 30 15 0 + 180 210 F r u i t S i z e (gm) F i g . 2. Scattergram of percentage breakdown versus f r u i t s i z e (ym) i n i r u i t dipped i n calcium c h l o r i d e . Dip Bd = 57.72 - 1.08 Dip Wt + 0.0052 Dip Mr2 (r2 = 0.56) 92 F i g . 3. Scattergram of f l e s h firmness i n f r u i t , dipped i n calcium c h l o r i d e versus that i n c o n t r o l f r u i t (kg). Dip Press = 1.70 + 0.64 C o n t r o l Press (r2 = 0. 48) 93 100 + 1 1 / * 1 2 / 1 . 1 1 >^ 1 60 + 1 / + 1 1 1 2 1 > ^ [ 1 1 1 1 1 60 + 1 1 2 1 + 1 1 1 1 y *l 2 1 1 s 1 1 40 •• 1 1 1 1 1 1 1 1 1 1 1 20 + 1 1 / 1 1 2 1 1 . 1 1 1 1 1 1 2.5 137.5 162. 5 137.5 212.5 1.25. 0 150. 0 175.0 200.u 2 2 D . 0 S i z e o f C o n t r o l F r u i t (qm) F i g . 4. S c a t t e r g r a m o f p e r c e n t a g e b r eakdown i n c o n t r o l f r u i t v e r s u s f r u i t s i z e (gm). C o n t r o l Bd - -77.15 + 0.83 C o n t r o l Wt ( r 2 •= 0.50) 

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