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Some effects of temperature on flower production, compatibility relations and pollen development in… Guccione, Gioacchino Maria 1959

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SOME EFFECTS OF'TEMPERATURE ON FLOWER PRODUCTION, COMPATIBILITY RELATIONS AND POLLEN DEVELOPMENT IN CERTAIN LINES OF THE TOMATO (Lyoopersipon esculentunuMill.)  by GIOACCHINQ MARIA GUCCIONE  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN AGRICULTURE i n t h e Department of Horticulture  We accept t h i s t h e s i s as conforming t o t h e standard r e q u i r e d from candidates f o r t h e degree o f MASTER OF SCIENCE IN AGRICULTURE  THE UNIVERSITY OF BRITISH COLUMBIA May 1959  ABSTRACT The development of tomato v a r i e t i e s i s d e s i r e d f o r comm e r c i a l p r o d u c t i o n i n a g r i c u l t u r a l areas h a v i n g r e l a t i v e l y low s p r i n g temperatures, and/or s h o r t growing seasons.  These  v a r i e t i e s would need the c h a r a c t e r of being a b l e t o s e t f r u i t under the u n f a v o r a b l e c o n d i t i o n s of temperatures below 65 F.. The E n g l i s h v a r i e t y . Puck , has the c h a r a c t e r i s t i c o f s e t t i n g fru.it a t low temperatures, but i s otherwise u n s u i t a b l e f o r p r o f i t a b l e tomato p r o d u c t i o n .  To i d e n t i f y the mechanism o f  t h i s d e s i r a b l e c h a r a c t e r i n Puck, and mode o f i n h e r i t a n c e of the c h a r a c t e r , experiments were c a r r i e d out t o study f l o w e r production, p o l l e n c o m p a t i b i l i t y duction,  r e l a t i o n s h i p s , ' and  development and g e r m i n a t i o n of p o l l e n .  Experiments were c a r r i e d out a t two temperature i n greenhouses ment.  the p r o -  levels  t o observe e f f e c t s on f l o w e r and f r u i t develop-  These p l a n t responses were s t u d i e d I n a r e l a t i v e l y c o o l  greenhouse kept a t 55°- 65* P. and i n another house kept a t 65 75°P. range which i s c o n s i d e r e d optimum f o r tomato p r o d u c t i o n . The p l a n t s used were Puck and Bonny Best v a r i e t i e s and t h e i r r e c i p r o c a l F1 h y b r i d s . Blower p r o d u c t i o n was s i g n i f i c a n t l y Increased by lower temperatures, and the i n c r e a s e s on Puck and the h y b r i d s were l a r g e r than on Bonny Best.  F r u i t s e t t i n g was reduced by low  temperatures, suggesting r e d u c t i o n ^ o f s e l f - c o m p a t i b i l i t y I n the h y b r i d s as w e l l as i n Bonny Best, the l a t t e r having a h i g h ii  percentage  of p a r t h e n o c a r p i c f r u i t s .  The number of days  between p o l l i n a t i o n and m a t u r i t y of f r u i t s was found to be i n v e r s e l y r e l a t e d to the number of seed formed i n the f r u i t s . Low temperatures, probably i n t e r a c t i n g w i t h low l i g h t i n t e n s i t i e s and s h o r t p h o t o p e r i o d s , appeared to reduce markedly the v i a b i l i t y of p o l l e n on a l l l i n e s , as shown by v i a b i l i t y t e s t s on the p o l l e n w i t h the acetocarmine s t a i n i n g procedure and w i t h g e r m i n a t i o n t e s t s i n v i t r o .  These experiments revea-  l e d an unexpected v a r i a b i l i t y i n p o l l e n g e r m i n a t i o n , which was p o s s i b l y due to the e f f e c t s of temperature on m i c r o s p o r o g e n e s i s . Percentages of normal meioses were only s l i g h t l y a f f e c t e d , but t h e r e was evidence t h a t a minimum temperature i s r e q u i r e d f o r the c o m p l e t i o n of m e i o s i s , and t h a t such minima were d i f f e r e n t f o r d i f f e r e n t meiotic stages.  Rates of p o l l e n d e t e r i o r a t i o n  f o l l o w i n g dehiscence of the anthers were found t o be d i f f e r e n t in different varieties. Puck had a h i g h e r number of f l o w e r s produced at low temper a t u r e s ,showed no r e d u c t i o n of s e l f - c o m p a t i b i l i t y , and had a c o n s i s t e n t seed s e t ; t h e r e f o r e , t h i s v a r i e t y i s to be c o n s i d e r e d a p o s s i b l e source of germ plasm i n the b r e e d i n g of tomatoes t o l e r a n t of c o o l temperatures.  In p r e s e n t i n g  t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of  the requirements f o r an advanced degree at the  University  of B r i t i s h Columbia, I agree t h a t 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 r e f e r e n c e and agree t h a t permission f o r e x t e n s i v e f o r s c h o l a r l y purposes may  study.  I further  copying of t h i s  be granted by the Head of  Department or by h i s r e p r e s e n t a t i v e s .  thesis my  I t i s understood  t h a t copying or p u b l i c a t i o n of t h i s t h e s i s f o r  financial  g a i n s h a l l not be allowed without my w r i t t e n permission..  Department of  :  The U n i v e r s i t y of B r i t i s h Columbia, Vancouver 8, Canada. Date  ACKNOWLEDGEMENT  The w r i t e r wishes t o express h i s thanks t o Dr.C.A. Hornby,Associate  P r o f e s s o r o f H o r t i c u l t u r e and Chairman o f  the t h e s i s Committee, f o r s u p e r v i s i o n o f the experimental work and f o r v a l u a b l e a s s i s t a n c e i n the p r e p a r a t i o n o f t h e thesis. Acknowledgement i s g i v e n t o the o t h e r members o f the t h e s i s Committee; Dr.Y.C, B r i n k , P r o f e s s o r o f Agronomy; Br.G.H. H a r r i s , P r o f e s s o r o f H o r t i c u l t u r e ; Dr. A.G. Renney, A s s o c i a t e P r o f e s s o r o f Agronomy;and Mr. E.L. Watson, A s s i s t a n t P r o f e s s o r o f A g r i c u l t u r a l Mechanics. Thanks a r e expressed  t o Dr. G.E. Rouse, I n s t r u c t o r ,  Department of B i o l o g y and Botany, and member of the t h e s i s Committee, f o r h i s h e l p i n the h i s t o l o g i c a l work; and t o Dr. J . Sawyer, D i v i s i o n o f p l a n t Science, f o r h i s v a l u a b l e cooperation. The w r i t e r i s indebted f o r f i n a n c i a l a s s i s t a n c e d u r i n g the course of the work t o the B r i t i s h Columbia E l e c t r i c Co. Ltd.  v  TABLE OB CONTENTS Page INTRODUCTION  1  LITERATURE REVIEW........  3  MATERIALS AND METHODS A.  Materials.  14  B.  Methods  16  1.  Greenhouse Experiments,  16  2.  C y t o l o g i c a l Experiments  19  a) M i c r o s p o r o g e n e s i s . . . . . . . . . . . . . . . . .  20  b) P o l l e n v i a b i l i t y  22  .....  c) P o l l e n g e r m i n a t i o n . . . . . .  23  RESULTS 1.  Greenhouse Experiments, a) E f f e c t s of temperature on f l o w e r production.  27  b) E f f e c t s o f temperature on compat i b i l i t y relationships  39  c) E f f e c t s o f seed s e t on e a r l i n e s s of f r u i t s 2.  44  C y t o l o g i c a l Experiments. a) M i c r o s p o r o g e n e s i s . .  ,.».....  47  b) P o l l e n v i a b i l i t y  50  c) P o l l e n g e r m i n a t i o n .  52  DISCUSSION  57  SUMMARY AND CONCLUSIONS  64  LITERATURE CITED.  6  iv  7  INTRODUCTION The p r o d u c t i o n o f tomato v a r i e t i e s which can s e t f r u i t under c o n d i t i o n s o f r e l a t i v e l y low temperature i s o f p a r t i c u l a r importance i n "breeding new v a r i e t i e s f o r i n t r o d u c t i o n i n Canada. Unfavorable c o n d i t i o n s o f temperature p r e v a i l i n g i n the e a r l y p a r t o f the growing s e a s o n , f r e q u e n t l y c o n s t i t u t e the main l i m i t i n g f a c t o r f o r growing tomatoes.This crop has two b a s i c temperature r e q u i r e m e n t s j f i r s t l y , a f r o s t - f r e e p e r i o d of about three and one h a l f months;secondly,a minimum temperature r e quirement o f approximately 55" F. I n the t r a d i t i o n a l areas o f c u l t u r e f o r t h i s crop i n Canada t h e r e i s a s u f f i c i e n t l y l o n g , f r o s t - f r e e p e r i o d f o r the p r o d u c t i o n o f tomatoes,but p l a n t s of the p r e s e n t commercial v a r i e t i e s v e r y o f t e n f a i l t o s e t f r u i t on the f i r s t and second i n f l o r e s c e n c e s , w h e n exposed t o n o c t u r n a l temperatures between 55° and 65°F,which v e r y f r e q u e n t l y occur i n the f i e l d a t t r a n s p l a n t i n g time,and f o r a few weeks subsequently.Therefore,growers would b e n e f i t i f f r u i t s e t t i n g were c o n s i s t e n t d u r i n g t h i s p e r i o d , r e s u l t i n g i n a b i l i t y o f growers t o supply the e a r l y , more l u c r a t i v e market,and t o i n c r e a s e t o t a l y i e l d s . F u r t h e r m o r e , the  i n c r e a s e d range o f temperature t o l e r a n c e would a l l o w the  e x t e n s i o n o f the c u l t u r e o f the tomato t o areas where,at the present time,the s h o r t season c o n s t i t u t e s the l i m i t i n g f a c t o r f o r economic growing. I t i s a l r e a d y known t h a t an E n g l i s h v a r i e t y , P u c k , c a n t o l e r -  - 2 ate r e l a t i v e l y low temperatures when s e t t i n g f r u i t . S t u d i e s have "been c a r r i e d out to a s c e r t a i n the s u i t a b i l i t y of t h i s v a r i e t y f o r use as a source of d e s i r a b l e germ plasm i n a breedi n g programme aiming to produce v a r i e t i e s more t o l e r a n t of c o o l temperatures f o r f r u i t s e t t i n g . S u c h  a programme r e q u i r e s  a c l e a r i d e n t i f i c a t i o n of the c h a r a c t e r , o r i n Puck,and knowledge  characters present  of the mode of i n h e r i t a n c e , a l l of which  would make p o s s i b l e the t r a n s f e r r i n g o f the d e s i r a b l e or c h a r a c t e r s , t o  character  e x i s t i n g v a r i e t i e s which are otherwise s a t i s -  f a c t o r y f o r commercial  production.  F r u i t s e t t i n g i s a sequence of many p r o c e s s e s . l t has been p o s s i b l e t o i n v e s t i g a t e only a few of the s e v e r a l p h y s i o l o g i c a l steps i n v o l v e d . P r e s e n t s t u d i e s were c o n f i n e d  to blossom and  f r u i t development as a f f e c t e d by temperature,and to c y t o l o g i c a l i n v e s t i g a t i o n s of p o l l e n p h y s i o l o g y and behaviour.  - 3 LITERATURE .REVIEW The tomato i s remarkably p l a s t i c i n i t s response to the environment.This p l a s t i c i t y r e s u l t s i n a l a r g e i n f l u e n c e upon the phenotypic  environmental  e x p r e s s i o n of i t s r i c h ,  genetic  v a r i a b i l i t y . S u c h I n t e r a c t i o n between g e n e t i c c o n s t i t u t i o n and environment accounts f o r p l a n t s appearing normal under one  set  of c o n d i t i o n s , a n d extremely d i f f e r e n t under changed c o n d i t i o n s . T h i s phenomenon i s p a r t i c u l a r l y t r u e of the d e l i c a t e  processes  involved i n f r u i t setting,namely:floral i n d u c t i o n , i n i t i a t i o n , development,and biology.The  complexity of r e l a t i o n s h i p s between  f a c t o r s i n v o l v e d i n phenotypic  e x p r e s s i o n has f r e q u e n t l y caused  the appearance of c o n f l i c t i n g r e p o r t s , r e f l e c t i n g the p l u r a l i t y of approaches and  interpretations,  F l o r a l i n d u c t i o n and  initiation.  The work of Lewis (30) was environmental  designed to study the g e n e t i c -  i n t e r a c t i o n e f f e c t s upon the c h a r a c t e r "number  of f l o w e r s per cluster".Temperature  and l i g h t i n t e n s i t y , a n d / o r  day l e n g t h m o d i f i e d the e x p r e s s i o n of the genotype.Temperatures around 14°0.during the growing p e r i o d from the expansion  of  cotyledons to the appearance of the f i r s t i n f l o r e s c e n c e r e s u l t e d i n p r o d u c t i o n of a h i g h e r number of f l o w e r s per c l u s t e r , t h a n f o r p l a n t s kept at 25-30" C.Lewis (29)  found t h i s c h a r a c t e r to  be c o n t r o l l d by a major gene,and by a system of e  Went's (48)  polygenes.  c o n c l u s i o n s do not agree w i t h those of L e w i s , r e l a t -  i n g f l o r a l i n d u c t i o n and i n i t i a t i o n ^ o n l y to g e n e t i c f a c t o r s . Kurk and Wittwer (23),extended the experiments to twelve  - 4 v a r i e t i e s s u b j e c t e d to d i f f e r e n t thennoperiods,and  concluded  t h a t lower temperatures at n i g h t g e n e r a l l y i n c r e a s e the number of f r u i t s per c l u s t e r . T h e response to temperature,however,was s t r i c t l y dependent upon v a r i e t a l c h a r a c t e r i s t i c s , o r genotypes. Thus three of the v a r i e t i e s r e a c t e d i n completely  opposite  f a s h i o n t o the o t h e r n i n e . W e l l e n s i e k (47) c i t e s work by Verkerk t h a t r e l a t i v e l y  low  l i g h t i n t e n s i t y depresses growth r a t e , d r y weight,number and weight of f r u i t s , a n d i n g e n e r a l p h y s i o l o g i c a l processes are dependent upon  carbohydrate  which  availability.  F l o r a l development. Normally  developed tomato f l o w e r s are hypogynous,and r e g -  u l a r . The number of f l o r a l p a r t s i n each c y c l e i s v a r i a b l e i n c u l t i v a t e d v a r i e t i e s (15),although solanaceous p l a n t s are u s u a l l y pentamerous,with a b a s i c f l o r a l plans 5,5,5,2.Cooper (8)  and  Smith (41) have d e s c r i b e d hexamerous development as the most commonly o c c u r r i n g form i n commercial v a r i e t i e s . The ontogeny and normal f l o r a l development of the tomato have been f u l l y d e s c r i b e d by Hayward ( 1 5 ) . F a s c i a t i o n i n the p e r i a n t h and i n the f e r t i l e p a r t s of the f l o w e r have been desc r i b e d by Z i e l i n s k i (51),who i d e n t i f i e d the causes as low temper a t u r e s and extremes i n the > carbohydrate  /nitrogen ratio  having d i f f e r e n t e f f e c t s on d i f f e r e n t genotypes.Sepals and a l s i n f a s c i a t e d f l o w e r s may  pet-  be present i n exaggerated or redu-  ced number,and p e t a l s are sometimes l a c k i n g , o r m o d i f i e d i n shape. Stamens seem to be very s e n s i t i v e t o environmental  influen-  c e s , and any cause a f f e c t i n g normal p r o d u c t i o n o f . p o l l e n i s l i k e l y t o a f f e c t normal development o f a n t h e r s .  Howiett (18')  s t a t e d t h a t carbohydrate d e f i c i e n c i e s r e s u l t sometimes i n s u p p r e s s i o n o f the male organs, thus becoming a l i m i t i n g f a c t o r i n the s e x u a l e x p r e s s i o n of tomato p l a n t s .  He r e p o r t e d f l o r a l  a b s c i s s i o n a t bud stage under v e r y severe carbohydrate s h o r t age.  I n c r e a s i n g a v a i l a b i l i t y of carbohydrates r e s u l t e d p r o g r e s -  s i v e l y i n blossoms r e a c h i n g a n t h e s i s , i n c r e a s i n g percentages o f v i a b l e m i c r o s p o r e s , and f i n a l l y i n the p r o d u c t i o n o f normal pollen grains.  Microspore degeneration was found a t any time  f o l l o w i n g the second m e i o t i c d i v i s i o n , and f r e q u e n t l y n o r m a l l y appearing g r a i n s were found t o be n o n - f u n c t i o n a l . As p o s s i b l e causes o f carbohydrate shortage, Judkins (22) suggested p e r i o d s of low l i g h t i n t e n s i t y which reduced p r o d u c t i o n o f v i a b l e p o l len.  Johnson et a l . ( 2 1 ) found cases where sugar t r a n s l o c a t i o n  from the l e a v e s was impaired by n o c t u r n a l temperatures. I n g e n e r a l , carbohydrate shortage d u r i n g the process o f p o l l e n m a t u r a t i o n i n tomato p l a n t s appeared t o r e s u l t i n reduced p o l l e n v i a b i l i t y . Gametic s t e r i l i t y i s l a r g e l y r e s p o n s i b l e f o r u n f r u i t f u l ness r e f l e c t i n g chromosome imbalance of some tomato l i n e s ( 3 6 ) . Gene mutation i n the broad sense i s r e s p o n s i b l e f o r s t e r i l i t y of some d i p l o i d p l a n t s t o an extent which o n l y r e c e n t l y has been a p p r e c i a t e d . There are many r e p o r t s on gene m u i a t i o n a f f e c t i n g charac-  - 6 t e r s of the f l o w e r and o f the i n f l o r e s c e n c e  (14,24,27,37).  F i v e a s y n a p t i c mutants d e s c r i b e d by Soost (44) are o f cytogen e t i c i n t e r e s t . P o l l e n s t e r i l i t y i n those mutants was produced by reduced chromosome p a i r i n g i n e a r l y m e i o t i c stages.A c l e i s t o gamous mutant,in which no a n t h e s i s occurs,has been r e p o r t e d by R i c k and Robinson (38),under c e r t a i n f i e l d c o n d i t i o n s ; a n d Bishop (1) d e s c r i b e d the r e d u c t i o n o f stamens t o vestiges.Paddock and Alexander (34) d e s c r i b e d a mutant i n which i n f l o r e s c e n c e s kept growing and branching w i t h o u t p r o d u c i n g any f l o w e r s . F a s c i a t i o n of the p i s t i l occurs f r e q u e n t l y on p l a n t s grown at low temperatures (51).Supranumerary  s t y l e s may be present i n  the same f l o w e r , u s u a l l y f u s e d a l o n g t h e i r length,and e x t r a - l o c u l e s may produce abnormally shaped o v a r i e s , a n d subsequent  fruits,  i f they are able t o develop. Among the anomalies o f the p i s t i l , h o w e v e r , t h e most f r e q u e n t l y discussed i s s t y l a r exserti)n.Cultivated v a r i e t i e s usually d i f f e r from w i l d types by h a v i n g t h e i r stigmas l o c a t e d w i t h i n the s t a m i n a l cone.It has been suggested (37) t h a t the change from a moderately c r o s s - p o l l i n a t e d s p e c i e s t o a c o n d i t i o n o f e x c l u s i v e s e l f - p o l l i n a t i o n , o c c u r r e d when t h e tomato was i n t r o duced i n Europe from South A m e r i c a . l t was p r o b a b l y due t o the change o f p o s i t i o n o f t h e stigma w i t h r e s p e c t t o the anthers t h a t c l o s e r imbreeding made i t p o s s i b l e t o f i x many r e c e s s i v e c h a r a c t e r s by which c u l t i v a t e d v a r i e t i e s d i f f e r from w i l d t y p e s . Burk (5) r e p o r t e d t h a t l e n g t h of the s t y l e i n Bonny Best  - 7 v a r i e d a c c o r d i n g to the l e n g t h of the photoperiod,and t o the i n t e n s i t y of l i g h t ; 8 hours of p h o t o p e r i o d g i v i n g l o n g e r s t y l e s than 12 hours.Low l i g h t i n t e n s i t y was found to produce  effects  s i m i l a r t o those of s h o r t photoperiod.He suggested the a c t i o n of polygenes c o n t r o l l i n g s t y l a r e l o n g a t i o n . S i m i l a r o b s e r v a t i o n s were made by Bouquet (3) and Smith (40).The l a t t e r r e p o r t e d the e f f e c t s of the i n t e r a c t i o n between h i g h temperatures and low h u m i d i t y produced by h o t , d r y winds, r e s u l t i n g i n abnormal s t y l a r e l o n g a t i o n even before a n t h e s i s , i n such a way r e d u c i n g f r u i t s e t through i m p a i r e d p o l l i n a t i o n , r e t a r d e d tube growth,and f l o r a l a b s c i s s i o n , Howlett (18) found n i t r o g e n d e f i c i e n c y much more e f f e c t i v e i n b r i n g i n g about s t e r i l i t y of the female sex c e l l s than carbohydrate shortage,and subsequently found n i t r o g e n / c a r b o h y d r a t e imbalance t o be the cause of s t y l a r e l o n g a t i o n ( 1 9 ) . C o n d i t i o n s i m p a i r i n g carbohydrate s y n t h e s i s or r e s u l t i n g i n 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 n d any o t h e r c o n d i t i o n p r o d u c i n g temporary carbohydrate shortage,would r e s u l t i n p r o t r u s i o n of the stigma beyond the anther tube. Tang and Bonner (45) r e p o r t e d on the a c t i o n of an enzyme i n a c t i v a t i n g i n d o l e a c e t i c a c i d i n e t i o l a t e d pea s e e d l i n g s . They..found,also,a w a t e r - s o l u b l e , t h e r m o s t a b l e f a c t o r which i n h i b i t s the enzymatic i n a c t i v a t i o n of the i n d o l e a c e t i c a c i d i n a l l p l a n t s i n v e s t i g a t e d . T h e f o r m a t i o n of t h i s f a c t o r i s promot e d by l i g & t ;longer exposures t o l i g h t lower the amount of a c t i v e enzyme,so enhancing the a c t i o n of the i n d o l e a c e t i c  - 8 acid.Johnson and H a l l (21)  i n v e s t i g a t e d the mechanism of i n -  a c t i v a t i o n of the i n d o l e a c e t i c a c i d by enzymes i n the tomato and they r e l a t e d the s t y l a r e l o n g a t i o n to the h i g h temperatures and l i g h t i n t e n s i t i e s .Leopold and S c o t t (25)  found no  effects  of a u x i n shortage on f r u i t s e t , b u t thought the s e t t i n g and development of f r u i t was c o n t r o l l e d by the carbohydrate s u p p l y . R i c k and Robinson (38)  d e s c r i b e d a mutant showing abnormal  s t y l a r e l o n g a t i o n , a n d t h i s c h a r a c t e r was v e r y s e n s i t i v e to the a c t i o n of the environment.Soost (44) found reduced ovule f e r t i l i t y i n the f i v e a s y n a p t i c mutants. F i n a l l y , o f g r e a t g e n e t i c a l importance,on the same s u b j e c t of s t y l a r e l o n g a t i o n i s the r e p o r t by Currence (10) e x p l a i n i n g the  i n h e r i t a n c e of t h i s c h a r a c t e r on the b a s i s of a d u p l i c a t e  gene i n t e r a c t i o n . F l o r a l biology. Dehiscence of the anthers begins i n the tomato 24 t o 48 hours a f t e r the opening of the c o r o l l a , u n d e r o p t i m a l e n v i r o n mental c o n d i t i o n s ( 4 1 ) . S e l f - p o l l i n a t i o n i s the r u l e i n c u l t i v a t e d v a r i e t i e s , b u t moderate c r o s s - p o l l i n a t i o n may occur through the agency of i n s e c t s , t h e bumble-bee being the most common v i s i t a n t . Unfavorable c o n d i t i o n s may  i m p a i r the e f f i c i e n c y of the  p o l l i n a t i o n mechanism by c a u s i n g r e d u c t i o n i n p o l l e n g e r m i n a t i o n , and s l o w i n g the r a t e of tube growth;thus making f r u i t - s e t t i n g a process extremely s e n s i t i v e to the a c t i o n of the environment. The growth of p o l l e n tubes i s r e l a t i v e l y slow,even a t optimum temperatures.According to Smith and Cochran of 70"to 85"F.permit  (42),temperatures  the h i g h e s t percentage of p o l l e n germin-  ation;and 70°P.allow the maximum r a t e o f growth of the p o l l e n tube.Under f a v o r a b l e c o n d i t i o n s no case was found where f e r t i l i z a t i o n could be observed l e s s than 50 hours a f t e r p o l l i n a t i o n , Judkins (22) observed an i n c r e a s e i n the time i n v o l v e d i n p o l l e n tube growth d u r i n g f a l l and winter,when l i g h t i s of low i n t e n s i t y . H e d i d not attempt t o e x p l a i n those o b s e r v a t i o n s e i t h e r on the b a s i s o f s t y l a r anatomy o r p o l l e n v i a b i l i t y . A c c o r d i n g t o Went ( 4 8 ) , t h e r m o p e r i o d i c i t y i n tomatoes i s due t o the predominance of two d i f f e r e n t processes,one a dayl i g h t process,and the other a dark process,of which the dark process has a much lower temperature optimum than the l i g h t p r o cess .This r e l a t i o n h o l d s f o r p l a n t growth,as w e l l as f o r f r u i t s e t . F u r t h e r m o r e , i t was n o t i c e d t h a t a r t i f i c i a l l i g h t when a p p l i e d d u r i n g the c o o l n i g h t p e r i o d , c o m p l e t e l y  inhibited fruit  formation.  The i n v e s t i g a t i o n s of Leopold and S c o t t (25) l e d t o t h e c o n c l u s i o n t h a t besides the w e l l known t e m p e r a t u r e - s e n s i t i v e f u n c t i o n s , s u c h as growth o f the s t y l e , r e d u c e d p o l l e n v i a b i l i t y , and i n h i b i t i o n of p o l l e n tube growth,there i s an Inherent temper a t u r e s e n s i t i v i t y i n the tomato ovary i t s e l f . T h i s was found t o be independent of the a v a i l a b l e n u t r i t i v e m a t e r i a l s . Parthenocarpy i s not uncommon i n the tomato,but the f r u i t s produced are u s u a l l y s m a l l , o r of poor quality.However,Hawthorn (16)  r e p o r t e d t h a t a cross between Large Cherry and Bonny Best  v a r i e t i e s , p r o d u c e d seedless,good  q u a l i t y and abundant f r u i t s i n  midsummer.The same p l a n t s had e a r l y and l a t e maturing f r u i t s  - 10 with, seeds. A c c o r d i n g t o G-ustafson ( 1 3 ) , a u x i n content of the o v a r i e s may he h i g h enough t o s e t o f f the growth processes of the ovary, even i n the absence of f e r t i l i z a t i o n . A u x i n s f o r f u r t h e r growth are subsequently produced i n the ovary i t s e l f or i n the l e a v e s . Such c o n c l u s i o n s are supported by K i t s c h ' s work (33).He induced parthenocarpy i n v i t r o by the a d d i t i o n of s y n t h e t i c growth substances to n u t r i e n t s o l u t i o n s of u n p o l l i n a t e d , e x c i s e d tomato ovaries. There i s evidence t h a t p a r t h e n o c a r p i c f r u i t s , b e s i d e s b e i n g s m a l l e r i n s i z e and weighing l e s s than seeded ones,are  later  r i p e n i n g (46),a c h a r a c t e r of primary importance i n the development of new v a r i e t i e s f o r e a r l y p r o d u c t i o n under low s p r i n g temperatures. E f f e c t s of temperature on p o l l e n g e r m i n a t i o n and tube growth. There i s evidence t h a t temperature may have an e f f e c t on the t o t a l amount of tube growth as w e l l as on the r a t e of growth(42). The e f f e c t s of low temperatures on o t h e r crops such as plums and apples have been r e p o r t e d as a l t e r a t i o n s of v a r i e t a l f e r t i l i t y r e l a t i o n s h i p s produced by d i f f e r e n t e c o l o g i c a l c o n d i t i o n s (39). I n the tomato the optimum temperature f o r p o l l e n germinat i o n was found t o be 85" E.,whereas the maximum growth r a t e occurs at 70° E . , g r a d u a l l y d e c l i n i n g at both lower and h i g h e r temper a t u r e s (42).  -  11  -  Lewis (28) obtained marked d i f f e r e n c e s between the growth r a t e s of compatible and i n c o m p a t i b l e p o l l e n tubes w i t h i n the same s t y l e , b y c u l t u r i n g p o l l i n a t e d f l o w e r s at d i f f e r e n t temperatures.The r a t e of growth of compatible tubes i d g e n e r a l l y i n c r e a s e d f o l l o w i n g temperature i n c r e a s e s , a n d f a l l s r a p i d l y when the l e t h a l temperature i s approached.Incompatible p o l l e n tubes have o p p o s i t e b e h a v i o u r ; t h u s , a t optimum t e m p e r a t u r e s , d i f f e r e n c e s i n l e n g t h beween the two types of p o l l e n tubes are at t h e i r maximum. Richardson and Currence ( 3 5 ) , f o l l o w i n g a s i m i l a r approach succeeded i n d i f f e r e n t i a t i n g f o r e a r l i n e s s i n progenies of F1 hybrids.They found s m a l l but s i g n i f i c a n t d i f f e r e n c e s i n e a r l i ness of P2 p l a n t s grown from seeds taken from stem h a l v e s as compared to p l a n t s grown from seed i n blossom h a l v e s of the same f r u i t s . V a r i e t a l d i f f e r e n c e s i n a b i l i t y of p o l l e n to s e t f r u i t s over more o r l e s s w i d e r ranges of temperature has been shown by Bonn ( 2 ) . P o l l e n from the e a r l y v a r i e t y 1159 was a b l e to s e t f r u i t on Pearson under temperatures at which Pearson p o l l e n was unable t o s e t f r u i t on both 1159 and Pearson. Hornby and Daubeny (17).working on Puck and Bonny Best v a r i e t i e s obtained data s u g g e s t i n g a g e n e t i c d i f f e r e n c e between the  two v a r i e t i e s i n p r o d u c t i o n of v i a b l e p o l l e n , g e r m i n a t i o n  of p o l l e n , a n d f e r t i l i z a t i o n at low temperatures. Meiosis. The behaviour of chromosomes at m e i o s i s has been s t u d i e d  mainly on p o l l e n mother c e l l s , a n d was as e a r l y as  1926.Prior  s t a r t e d by L e s l e y ( 2 6 )  to t h a t time,Winkler  (49)  had  discovered  t h a t the tomato has -a somatic number of 24»and a gametic number of 1 2 chromosomes.Meiosis i n the tomato f o l l o w s the r e g u l a r p a t t e r n f o r angiosperms (37).Chromosomes become d i f f u s e and i n d i s t i n g u i s h a b l e i n interphase,and  separate at the second d i v i -  s i o n to g i v e t e t r a d groups of 1 2 chromosomes e a c h . C y t o k i n e s i s f o l l o w s , a n d a f t e r a p e r i o d of maturation,microspores  are r e l e a -  sed. The  s t a r c h r i c h , , .opaque l a y e r i n the w a l l s of the mature  microspores  does not a l l o w f o l l o w i n g the f i r s t p o s t m e i o t i c  mito-  s i s , about which very l i t t l e i s known;the g e n e r a t i v e nucleus which i s o r i g i n a t e d i n the f i r s t m i t o s i s ,again d i v i d e s i n the growing p o l l e n tube. B i v a l e n t p a i r i n g n o r m a l l y occurs at a l l stages between zygotene and metaphase of the f i r s t m e i o t i c d i v i s i o n . A few  ex-  c e p t i o n s to t h i s r u l e occur owing to abnormal c o n d i t i o n s such as h e t e r o p l o i d y , g e n e - c o n t r o l l e d chromosome d i s t u r b a n c e s , o r subl e t h a l temperatures (37).Soost 95°1?  (44) found temperatures around  .were more e f f e c t i v e than temperatures around 50°  P.  for  pro-  ducing a b n o r m a l i t i e s i n m e i o s i s . A c c o r d i n g to Hayward  (15),it  i s t y p i c a l of the second r e -  d u c t i o n d i v i s i o n i n the tomato,that metaphase,anaphase,and t e l o phase may  occur s i m u l t a n e o u s l y i n a s i n g l e l o c u l e .  Cytoplasmic i n h e r i t a n c e . E x t r a n u c l e a r i n h e r i t a n c e i n the tomato i s not f u l l y under-  - 13 stood y e t , d e s p i t e i t s r a t h e r frequent occurrence.The main d i f f i c u l t y a r i s e s from i n c o m p a t i b i l i t y b a r r i e r s which a l l o w crosses of many combinations t o be made i n one d i r e c t i o n o n l y . C h l o r o p h y l l d e f i c i e n c i e s have been found t o be i n h e r i t e d i n maternal f a s h i o n , b e i n g t r a n s m i t t e d t o progeny o n l y i f t h e p i s t i l l a t e parent were d e f i c i e n t , r e g a r d l e s s of the c o n d i t i o n of the male parent ( 3 1 ) . Transmission  of such c h a r a c t e r s as p l a n t h e i g h t , y i e l d s ,  and f r u i t shape,in some i n s t a n c e s have been e x p l a i n e d on the b a s i s of cytoplasmic i n h e r i t a n c e . I n these cases P1 h y b r i d s o f one mating s i g n i f i c a n t l y d i f f e r e d from the r e c i p r o c a l s obtained i n the o t h e r mating o f the same i n t e r v a r i e t a l cross ( 3 7 ) .  - 14 MATERIALS AND METHODS A. M a t e r i a l s . The p l a n t m a t e r i a l s used i n the experiments were the tomato v a r i e t i e s : P u c k and Bonny Best,and t h e i r r e c i p r o c a l P 1 h y b r i d s . Puck. Puck was i n t r o d u c e d from England,where  I t had been d e s c r i -  bed by Crane (9).Puck was s e l e c t e d from s e g r e g a t i n g progenies of crosses between the American v a r i e t y , V i c t o r ,and an u n i d e n t i f i e d v a r i e t y r e l e a s e d from R u s s i a at the end of World War I I . Puck has a determinate growth h a b i t and i s c h a r a c t e r i z e d by a woody stem,strong enough t o bear the weight of the f r u i t s i n the early p e r i o d of growth.The main stem terminates l e a f and c a r r i e s a double i n f l o r e s c e n c e i n the l a s t A x i l l a r y side-shoots  in a  internode.  develop from buds,and have determinate .  growth as well.They may c a r r y s i n g l e c l u s t e r s , b u t i n the l a s t internode  double ones u s u a l l y occur.The indeterminate  h a b i t of  growth i s c o n d i t i o n e d by a s i n g l e r e c e s s i v e gene sp ( f o r s e l f pruning) , l o c a t e d i n the s i x t h chromosome,and belonging t o the f o u r t h l i n k a g e group ..(37,50) .Leaves are dark  green,thick,with  a c h a r a c t e r i s t i c roughness of s u r f a c e . B r u i t s i z e i s medium, c o l o u r uniform, and shape sometimes I r r e g u l a r .The f r u . i t w a l l i s d i f f e r e n t i a t e d from the p l a c e n t a and at m a t u r i t y the l a t t e r l a c k s the f l e s h y c h a r a c t e r of commercial v a r i e t i e s . The Puck v a r i e t y , d e s c r i b e d as an e a r l y producer,has been shown t o r e q u i r e a g r e a t e r number of days between blossoming  - 15 and r i p e n i n g when compared to other v a r i e t i e s under B r i t i s h Columbia growing c o n d i t i o n s ( 1 1 ) . Puck has been found to be d e f i n i t e l y i n f e r i o r to commerc i a l v a r i e t i e s a l r e a d y grown i n the p r o v i n c e of B r i t i s h Columbia, d e s p i t e i t s aknowledged c h a r a c t e r of being able t o s e t f r u i t s a t low temperatures  (12).On the o t h e r h a n d , i t i s t h i s c h a r a c t e r  t h a t makes i t a p o t e n t i a l source o f v a l u a b l e germ plasm f o r improvement of v a r i e t i e s otherwise acceptable f o r commercial production.  •  Bonny B e s t . Bonny Best i s one of the w e l l known v a r i e t i e s on the North American continent,where  i t has been c u l t i v a t e d s i n c e the e a r l y  years of t h i s c e n t u r y , f o l l o w i n g i n t r o d u c t i o n by the f i r m of Johnson and Stkes o f P h i l a d e l p h i a . Bonny Best has i n d e t e r m i n a t e growth;round , f l e s h y , u n i f o r m l y c o l o u r e d f r u i t s . I t i s r e l a t i v e l y e a r l y , b u t very s e n s i t i v e to the e f f e c t s of low temperatures  on f r u i t setting.Bonny Best has been  chosen to r e p r e s e n t the commercial v a r i e t i e s because i n the past t h i r t y years a c o n s i d e r a b l e amount of r e s e a r c h has been done , i n which t h i s popular v a r i e t y was the t e s t p l a n t . F1 h y b r i d s . F i r s t g e n e r a t i o n h y b r i d s of Puck and Bonny Best were used to observe e f f e c t s of recombination,and  the r e c i p r o c a l crosses  allowed the study of p o s s i b l e maternal i n h e r i t a n c e . P l a n t s were grown from seeds obtained from c o n t r o l l e d crosses which were  c a r r i e d out i n p r e v i o u s years a t the U n i v e r s i t y of B r i t i s h Columbia.The h y b r i d s resemble Bonny Best p l a n t s i n t h e i r g e n e r a l appearance,have the indeterminate habit,and grow f a s t e r and t a l ler  than Bonny Best p l a n t s . L e a f w i d t h , t h i c k n e s s , s u r f a c e and  c o l o u r are i n t e r m e d i a t e between the same c h a r a c t e r s i n t h e parent varieties.  B. Methods. 1. Greenhouse  experiments.  The experiments were c a r r i e d on i n the greenhouses of the U n i v e r s i t y o f B r i t i s h Columbia i n the w i n t e r o f  1958-1959  to  c o n t r a s t response of the p l a n t m a t e r i a l s a t the r e l a t i v e l y c o o l temperatures of 55*to 6 5 " P . w i t h t h e n e a r l y optimum range o f 65" t o 7 5 * F. f o r t h e tomato.. Seeds o f the f o u r stocks,Puck,Bonny Best and t h e i r r e c i p r o cal" h y b r i d s were sown on November 24,1958,and s e e d l i n g s were p r i c k e d out and s e t i n 2x2" veneer bands i n f l a t s two weeks later.Temperature  ranges were kept as c l o s e l y as p o s s i b l e between  5 5 " and 65°P.for the c o o l house,and 6 5 ' a n d 75°F.for the warm house. Temperature records were obtained f o r the d u r a t i o n of the e x p e r i ments by means of thermographs.All  s e e d l i n g s were kept i n the  warm house u n t i l t r a n s p l a n t i n g time. C o n t r o l l e d p o l l i n a t i o n s were c a r r i e d out f o r the d u r a t i o n of two months.First p o l l i n a t i o n s were made on December 1,and December  29,in  the warm and i n the c o o l greenhouses r e s p e c t i v e l y ,  - 17 and c a r r i e d u n t i l the end of February.During t h i s time the temp e r a t u r e i n the c o o l house went above 65° P. on eleven p a r t i c u l a r l y b r i g h t days,but o n l y s i x times f o r p e r i o d s l o n g e r than one hour.Most of the time temperatures were i n the lower h a l f of the range between 60° F.and 55"F.In the warm house  temperatures  went below 65°at night,and o n l y f i v e times below 60°F.for v e r y short periods. The benches used f o r t h i s experiment were p a r a l l e l to the n o r t h - s o u t h w a l l s i n both houses,one r e p l i c a t e being along the n o r t h e r n and two along the southern w a l l i n each room.The benches were f i l l e d w i t h greenhouse compost,and supplemental phosphate f e r t i l i z e r was g i v e n i n the amount of one pound superphosphate on each bench,equivalent to 650 l b / a c r e . A n a l y s i s of a sample of the compost taken at t r a n s p l a n t i n g time had a pH value around 6,and h i g h contents of nitrogen,phosphorus,and  potassium.  The p l a n t s were s e t i n the benches on November 6,1958. i n d i v i d u a l p l o t s c o n s i s t e d of one plant,and a randomized b l o c k d e s i g n w i t h three r e p l i c a t i o n s was used i n each house.The p l a n of the experiment  i s shoam i n appendix I , P l a n t s were spaced  20 inches apart between rows,and 15 inches apart w i t h i n rows. To p r o v i d e supplementary  l i g h t under the seasonal c o n d i t i o n s  of decreasing l i g h t i n t e n s i t y and photoperiod,!our 500 watt f l u o r e s c e n t tubes were i n s t a l l e d i n p a i r s over each bench.Four hours e x t r a - i l l u m i n a t i o n were p r o v i d e d i n the morning and a l s o i n the evening to i n s u r e an eighteen hour photoperiod. A l l p l a n t s except those of the determinate Puck v a r i e t y  -  18  -  were pruned to a s i n g l e stem,and s t a k e d . The p o l l i n a t i o n s t u d i e s c o n s i s t e d of s i x t e e n treatments to have a l l f o u r l i n e s s e l f - p o l l i n a t e d and a l s o c r o s s - p o l l i n a t e d i n a l l p o s s i b l e combinations.The  s e r i e s of p o l l i n a t i o n treatments  are l i s t e d as f o l l o w s , s h o w i n g the maternal parent f i r s t , T h e l i s t of treatments shows corresponding symbols which w i l l be used f o r f u t u r e r e f e r e n c e t o the t r e a t m e n t s . Symbols.  Treatments. 1.  Puck x Puck  m  2.  Puck x Bonny Best  PxBB  3.  Puck x (Puck x Bonny B e s t )  FI  Px(PxBB)  4.  Puck x (Bonny Best x Puck)  Fl  Px(BBxP)  5.  Bonny Best x Bonny Best  BBS  6.  Bonny Best x Puck  BBxP  7.  Bonny Best x (Puck x Bonny B e s t )  8.  Bonny Best x (Bonny Best x Puck) ,  9.  (PuckxBonny Best) x(PuckxBonny  BBx(PxBB)  F(  BBx(BBxP)  F  fl  Best) , F  (PxBB)®  10.  (Puck x Bonny B e s t ) x Puck  (PxBB)xP  11.  (Puck x Bonny B e s t ) x Bonny Best  (PxBB)xBB  12.  (PuckxBonny Best) , x(Bonny B e s t x P u c k )  fl  (PxBB)x(BBxP)  13.  (Bonny Be stxPuck) x( Bonny BestxPuck)  F(  (BBxP)a  14.  (Bonny Best x Puck) x Puck  (BBxP)xP  15.  (Bonny Best x Puck) x Bonny Best  (BBxP)xBB  16.  (Bonny BestxPuck) x(PuckxBonny  R  Pl  F  Fl  Fl  fl  Fl  Second,third,and f o u r t h  Best)  FI  (BBxP)x(PxBB)  i n f l o r e s c e n c e s were p o l l i n a t e d  on each p l a n t . F i r s t c l u s t e r s were d i s c a r d e d because they were  - 19 w e l l developed a t the time o f t r a n s p l a n t i n g t o benches,and f l o w e r s opened i n both houses a few days l a t e r , t h u s development of those f l o w e r s would not have been i n f l u e n c e d by the c o n t r a s t i n g temperatures. The f o l l o w i n g procedure was used i n the c o n t r o l l e d p o l l i n ations.The f l o w e r s were emasculated one day before a n t h e s i s by t a k i n g away p e t a l s and anthers w i t h a p a i r of t w e e z e r s . P o l l e n was c o l l e c t e d on microscope s l i d e s , a n d a p p l i e d by d i p p i n g the stigmas on the mound o f p o l l e n on the s l i d e s . A p p l i c a t i o n s o f p o l l e n were repeated t w i c e on each f l o w e r a t two-days i n t e r v a l s i n o r d e r . t o reduce the e f f e c t s o f environmental v a r i a b l e s on p o l l e n . A l l p o l l e n used was produced i n the warm house.Blossoms were l a b e l e d t o make i t p o s s i b l e t o c o l l e c t t h e f o l l o w i n g data f o r each v a r i e t y i n each treatments i) ii) iii)  P o l l i n a t i o n treatment. Bate o f p o l l i n a t i o n , Number of days between p o l l i n a t i o n and f r u i t m a t u r i t y .  Other data recorded were: i)  Number of blossoms on f i r s t f o u r t r u s s e s .  ii)  Number o f seed p e r f r u i t ,  iii)  Percentages of p a r t h e n o c a r p i c f r u i t s . The data c o l l e c t e d were s u b j e c t e d t o a n a l y s i s of v a r i a n c e  as o u t l i n e d by Snedecor (43).Transformations were used when needed. 2.  C y t o l o g i c a l experiments.  C y t o l o g i c a l o b s e r v a t i o n s were made t o a s c e r t a i n the e f f e c t s  - 20 -  of d i f f e r e n t c o n d i t i o n s of temperature on m e i o s i s , v i a b i l i t y , and germination o f p o l l e n . a) M i c r o s p o r o g e n e s i s . M i c r o s p o r o g e n e s i s was s t u d i e d by means of a smear t e c h n i q u e . Buds were taken f o r examination a t a s i z e of approximately 4 mm. i n l e n g t h , a l t h o u g h the optimum s i z e f o r o b s e r v i n g the m e i o t i c stages was found t o v a r y among d i f f e r e n t v a r i e t i e s , a n d a c c o r d i n g t o the p o s i t i o n o f t h e bud on t h e i n f l o r e s c e n c e , a n d o f the l a t t e r on t h e p l a n t w i t h i n each v a r i e t y . Two d i f f e r e n t s t a i n i n g procedures were i n i t i a l l y a) B e l l i n g ' s iron-acetocarmine,and b) Feulgen's  used;  reagent,both  prepared u s i n g Johansen's formulae ( 2 0 ) . B e l l i n g ' s acetocarmine gave c o n s i s t e n t l y b e t t e r r e s u l t s , a n d was found t o be t i m e - s a v i n g as compared t o the use of Feulgen's reagent.Therefore the l a t t e r was discarded.The B e l l i n g ' s acetoca/mine  procedure was improved  by i n t r o d u c i n g the use of a Aft f e r r i c ammonium sulphate s o l u t i o n as a mordant,as suggested by Sooat ( 4 4 ) . The technique which gave the best r e s u l t s was as f o l l o w s . F l o r a l buds were taken when about 4 mm.long,placed i n a k i l l f i x s o l u t i o n c o n s i s t i n g of a 3s1 a c e t i c a c i d - a l c o h o l s o l u t i o n f o r about t h r e e hours,then washed i n tap water f o r twenty minut e s , and mordanted f o r one h o u r . A f t e r washing f o r twenty  minutes  anthers were d i s s e c t e d w i t h a needle i n a drop o f acetocarmine on a s l i d e , A f t e r p l a c i n g the c o v e r s l i p , a s l i d e was g e n t l y heated u n t i l m i c r o s c o p i c examination r e v e a l e d the optimum s t a i n i n g . S l i des were f i n a l l y s e a l e d w i t h f i n g e r n a i l p o l i s h , C . R . A . F . f i x a t i v e (20) was used w i t h the e x p e c t a t i o n of imp r o v i n g r e s u l t s w i t h the F e u l g e n s , b u t no b e n e f i t was o b t a i n e d . 1  The p a r a f f i n method, as o u t l i n e d by Johansen  (20)was used  f o r p r e p a r i n g permanent s l i d e s , b u t once a g a i n r e s u l t s were uns a t i s f a c t o r y w i t h Peulgen's,and no b e t t e r w i t h acetocarmine. Both s t a i n s f a i l e d t o d i f f e r e n t i a t e chromosomes w i t h i n the nuc l e i , and t h i s procedure was abandoned. The buds f o r c y t o l o g i c a l o b s e r v a t i o n s were taken from p l a n t of Puck,Bonny Best and the r e c i p r o c a l h y b r i d s grown i n pots and kept i n the sarnie greenhouses where p l a n t s f o r the p o l l i n a t i o n experiment were being grown,Eight p l a n t s of each l i n e were used and a d d i t i o n a l m a t e r i a l was taken from b u f f e r p l a n t s of t h e p o l l i n a t i o n experiment.Samples  were always taken simultaneous-  l y from the 4 l i n e s i n each house,to observe m a t e r i a l  undergo-  i n g m e i o t i c d i v i s i o n presumably under s i m i l a r c o n d i t i o n s o f environment.Only  some of the s l i d e s prepared had c e l l s d i v i d -  i n g and t h i s stage appeared to be dependent on the age o f the b u d s . A f t e r p r e l i m i n a r y o b s e r v a t i o n s , i t was noted t h a t the occurrence of d i v i d i n g c e l l s was h i g h e r i n samples taken i n the morning,therefore,buds were always c o l l e c t e d a t 11 a.m.for the studies. About one hundred s l i d e s f o r each v a r i e t y were examined under the microscope t o a s c e r t a i n the frequency of d e v i a t i o n s from r e g u l a r m e i o t i c p a t t e r n s as a f f e c t e d by temperature. O b s e r v a t i o n s were s t a r t e d i n the second h a l f of November when buds began t o reach appropriate  size,On each s l i d e s e v e r a l  hundred p o l l e n mother c e l l s were present,and some o f them, selected, a t random were c a r e f u l l y examined.The nature of occur1  -  22  -  r i n g a b n o r m a l i t i e s was recorded,but no attempt was made t o express the frequency of abnormally d i v i d i n g c e l l s as a percentage of the t o t a l number 'of c e l l s b)  examined.  P o l l e n v i a b i l i t y experiments.  P o l l e n v i a b i l i t y was t e s t e d w i t h the standard a c e t o c a r m i ne s t a i n i n g procedure i n which d a r k l y s t a i n e d g r a i n s are cons i d e r e d v i a b l e . T h i s procedure c o n s i s t s of d u s t i n g p o l l e n on a s l i d e , s o a k i n g i t i n a drop of a c e t o c a r m i n e , p l a c i n g a c o v e r s l i p and gently- h e a t i n g the s l i d e s before examining under the microscope .Empty ,non-viable g r a i n s e i t h e r do not s t a i n at a l l or show a l i g h t brown colour,depending on l a c k o f , o r low content of s t a r c h i n the w a l l s . T h e chromatic r e a c t i o n , i n f a c t , i s dependent on the presence or absence of s t a r c h i n the g r a i n s , a n d i t i s v e r y s i m i l a r to the c h a r a c t e r i s t i c r e a c t i o n of s t a r c h w i t h potassium i o d i d e - i o d i n e s o l u t i o n . The p o l l e n produced i n the warm house and t e s t e d f o l l o w i n g the o u t l i n e d technique was the same m a t e r i a l used i n the c o n t r o l l e d - p o l l i n a t i o experiment.Of the p o l l e n c o l l e c t e d on microscope s l i d e s from blossoms at anthesis,some was used f o r p o l l i n a t i o n , and the remainder used f o r t e s t i n g i t s v i a b i l i t y . Observations were s t a r t e d on "December u n t i l January  26,1959,at  11,1958  and c a r r i e d on  one-day i n t e r v a l s . O n e hundred  grains  were counted on each date f o r each tomato l i n e , a n d the numbers of v i a b l e g r a i n s expressed as a percentage of the t o t a l s counted.  - 25 I n the c o o l house the sampling technique was n e c e s s a r i l y changed,because p o l l e n p r o d u c t i o n was lower and l a t e r on a l l l i n e s , a n d e s p e c i a l l y on Bonny B e s t . I n f a c t , i t was necessary to w a i t u n t i l March to get p l a n t s of the f o u r s t o c k s contempor a n e o u s l y a t anthesis.On March 12,1959,ten f l o w e r s o f each v a r i e t y were taken f o r t e s t i n g p o l l e n v i a b i l i t y . Ranges and means o f t h e v a r i e t a l g e r m i n a t i o n percentages were c a l c u l a t e d f o r the data c o l l e c t e d a t both temperature levels. C o n s i d e r i n g H o w l e t t s (18) r e p o r t t h a t p o l l e n g r a i n s 1  which appear normal i n shape and e x t e r n a l appearance  are o f t e n  n o n - v i a b l e , i t was decided t o i n v e s t i g a t e the v i a b i l i t y o f the p o l l e n by conducting g e r m i n a t i o n experiments i n v i t r o . c)  P o l l e n g e r m i n a t i o n experiments.  Experiments on p o l l e n g e r m i n a t i o n were c a r r i e d out i n v i t r o because the procedure p e r m i t t e d the use of c o n t r o l l e d c o n d i t i o n s ; a n d the study o f some f a c t o r s a f f e c t i n g g e r m i n a t i o n c o u l d be observed b e t t e r than on p l a n t s i n the v a r i a b l e e n v i r o n ment o f t h e greenhouses.The o b j e c t i v e of these experiments was a) t o compare the e f f e c t s o f d i f f e r e n t temperatures on germin a t i o n o f p o l l e n o f d i f f e r e n t v a r i e t i e s , a n d b) by s e l e c t i o n of a p p r o p r i a t e time i n t e r v a l s , t o observe the speed of p o l l e n g e r m i n a t i o n o f the v a r i e t i e s . P o l l e n produced i n the warm house on Puck and Bonny Best was used. Temperatures  chosen f o r the experiments were as f o l l o w s ;  - 24 i ) 10°0. as the minimum r e q u i r e d temperature f o r tomato growing; i i ) 15° C. as the temperature f r e q u e n t l y o c c u r r i n g i n the f i e l d i n early spring; i i i ) 20°C. as the optimum temperature f o r p o l l e n g e r m i n a t i o n and growth,as found by Smith and Cochran (42).Such temper a t u r e s correspond t o 50°,59and 68°F.,and were o b t a i n e d w i t h i n a range of + 2°C. i n c o n t r o l l e d temperature chambers of the Botany Department of the U n i v e r s i t y of B r i t i s h  Columbia.  At f i r s t p o l l e n was observed at three-hour i n t e r v a l s , b u t i t soon became e v i d e n t , i n repeated o b s e r v a t i o n s , t h a t the i n tense l i g h t and/or the heat generated by the i l l u m i n a t o r was inhibiting  tube development.Therefore,only One count f o r each  s l i d e was taken,24 hours a f t e r p o l l e n was put to germinate, and the i n v e s t i g a t i o n s on g e r m i ^ h a t i o n speed were d i c o n t i n u e d . I n i t i a l experiments were t r i e d on a 30$ sugar s o l u t i o n c o n t a i n i n g 30 ppm.  of boron,as o u t l i n e d by Chiscon f o r germi-  n a t i o n of p o l l e n of Ly c o p e r s i con P imp i n e l l i f o l i u m (6),but the frequency of b u r s t tubes i n i n i t i a l stages of growth was  ex-  tremely h i g h and prompted a p r e l i m i n a r y i n v e s t i g a t i o n on the e f f e c t s of d i f f e r e n t c o n c e n t r a t i o n s of the media.A s e r i e s of media c o n t a i n i n g c o n c e n t r a t i o n s of 5,10,15,20,and 30$ sucrose i n 0.5$ agar,and 30 ppm.boron was prepared. P o l l e n of the two v a r i e t i e s was c o l l e c t e d from s e v e r a l blossoms,thoroughly mixed and dusted on microscope  slides.  Then drops of the d i f f e r e n t media at room- temperature were  were p l a c e d on the s l i d e s and the p o l l e n s t i r r e d i n t o the media.The s l i d e s were q u i c k l y i n v e r t e d over w e l l - s l i d e s and seal e d w i t h v a s e l i n e . T h e s e t e s t s f o r optimum sucrose c o n c e n t r a t i o n i n the media were c a r r i e d out i n t h e warm greenhouse,and  repli-  c a t e d on two dates.Counts were taken a f t e r 24 hours,and t h e medium c o n t a i n i n g 10$ sucrose was found t o g i v e the h i g h e s t percent of p o l l e n g e r m i n a t i o n , t h e r e f o r e , t h i s c o n c e n t r a t i o n was used i n subsequent experiments. With the "lOft sucrose c o n c e n t r a t i o n f u r t h e r i n v e s t i g a t i o n s showed t h a t i n absence o f boron no g e r m i n a t i o n took p l a c e . The procedure adopted f o r f u r t h e r experiments was as f o l l o w s . P o l l e n from f r e s h l y dehisced anthers was c o l l e c t e d , d u s t e d on s l i d e s , t h e n s t i r r e d i n a drop o f sucrose s o l u t i o n brought to room temperature.The  s l i d e s were i n v e r t e d on w e l l - s l i d e s ,  s e a l e d w i t h v a s e l i n e , a n d kept i n c o n t r o l l e d temperature chambers a t the t h r e e chosen l e v e l s f o r 24 hours.Counts were taken on a microscope f i t t e d w i t h a graded ocular,and g r a i n s i n which the l e n g t h of the p o l l e n tube was at l e a s t equal t o the diameter o f t h e g r a i n were c o n s i d e r e d t o have germinated ( 3 9 ) . The counts o f germinated p o l l e n were made on samples o f 200 g r a i n s , a n d t h i s experiment was repeated on f i v e d i f f e r e n t d a t e s . The g e r m i n a t i o n experiments y i e l d e d data showing a much h i g h e r v a r i a b i l i t y than was expected to occur i n p o l l e n produced at t h e temperature l e v e l o f the warm house.It appeared p o s s i b l e t h a t p h y s i o l o g i c a l age o f p o l l e n c o u l d have c o n t r i buted t o such v a r i a b i l i t y , b e c a u s e of d i f f e r e n t r a t e s o f dete-  - 26 r i o r a t i o n o c c u r r i n g a f t e r dehiscence of the anthers i n d i f f e r e n t v a r i e t i e s . T h e f o l l o w i n g experiment was set up t o i n v e s t i gate such a p o s s i b i l i t y . I n f l o r e s c e n c e s h a v i n g f l o w e r s at d i f f e r e n t stages of a n t h e s i s were chosen,and stages of a n t h e s i s were numbered.Pull  bloom was c o n s i d e r e d number 1,and i n c r e a -  s i n g numbers were assigned t o e a r l i e r stages,the h i g h e s t number being t h a t of the f l o w e r i n which p e t a l s were r e f l e x e d , and anthers a l r e a d y t u r n i n g yellow,though not y e t d e h i s c e d , the number of f l o w e r s i n i n t e r m e d i a t e stages v a r i e d between t h r e e and f i v e i n d i f f e r e n t c l u s t e r s . A v e r a g e percentages of g e r m i n a t i o n were o b t a i n e d from two counts of 200 p o l l e n g r a i n s per flower,and the experiment was repeated on t h r e e dates.  - 27  -  RESULTS A.  fireer^quse  Experiment.  a) E f f e c t s of temperature on f l o w e r  production.  The number of f l o w e r buds formed on Puck and Bonny Best was  found to be i n f l u e n c e d by temperature as shown i n the  da-  t a of t a b l e s I and II.The s t a t i s t i c a l a n a l y s i s of such data presented some d i f f i c u l t i e s . R e s p o n s e to d i f f e r e n t temperatures being the main concern of the e x p e r i m e n t , i t was  desirable  to combine data from the c o o l and the warm houses f o r s t a t i stical  evaluation.  However,it was  i m p o s s i b l e to s u b j e c t the data of t a b l e I  and I I to separate analyses  of variance,because i n both s e t s  the c o n d i t i o n of homogeneity of v a r i a n c e was not s a t i s f i e d as shown by B a r t l e t t ' s t e s t s f o l l o w i n g the  tables;therefore,the  d a t a were transformed by means of the logarithmic t r a n s f o r m a t i o n as shown i n t a b l e s I I I and IV.The B a r t l e t t ' s t e s t f o r the transformed data of t a b l e I I I g i v e s a  helow the value r e q u i -  r e d f o r s i g n i f i c a n c e at the 5$ l e v e l of confidence.The t r a n s f o r m a t i o n h a v i n g been s u c c e s s f u l , a combined a n a l y s i s of the d a t a of a l l f o u r v a r i e t i e s has been p o s s i b l e , a s g i v e n i n t a b l e I I I , a n d i t i s seen t h a t there were s i g n i f i c a n t d i f f e r e n c e s between v a r i e t i e s . T h e number of f l o w e r s per c l u s t e r formed at low temperature was  s i g n i f i c a n t l y g r e a t e r i n Puck than i n Bon-  ny Best,and the h y b r i d s . S i g n i f i c a n t d i f f e r e n c e s were shown f o r primary e f f e c t s of trusses,and  f o r the i n t e r a c t i o n v a r i e t y x  truss. By i n s p e c t i o n of the data i n t a b l e s I and I I I , i t i s e v i -  - 28 dent t h a t .the r e c i p r o c a l s were very s i m i l a r to Bonny Best, s u g g e s t i n g a mendelian type of i n h e r i t a n c e of the l e t t e r ' s genie c o n t r i b u t i o n to the g e n e t i c c o n s t i t u t i o n of the h y b r i d s . S i m i l a r l y i t can be deduced t h a t d i f f e r e n c e s between the hyb r i d s and Bonny Best are probably due to the c o n d i t i o n of h e t e r o z y g o s i t y of the h y b r i d s . The s i g n i f i c a n t l y g r e a t e r v a r i a n c e i n Puck data, as r e v e a l e d by B a r t l e t t ' s test,, l e a d s to the c o n c l u s i o n t h a t Puck i s s i g n i f i c a n t l y d i f f e r e n t from the other three l i n e s .  There-  f o r e , i t was necessary to separate the data of Puck from the o t h e r s , and t o analyse the l a t t e r s e p a r a t e l y .  This procedure  was p a r t i c u l a r l y necessary i n the case of the data i n t a b l e I I f o r which the l o g a r i t h m i c t r a n s f o r m a t i o n shown i n t a b l e IV f a i l e d to reduce the h e t e r o g e n e i t y of the v a r i a n c e .  -  29  -  Table I„Number of flower buds formed on f i r s t four trusses of Puck,Bonny Best,and their reciprocal hybrids grown at temperatures below 6 5 ° P . Variety p£ck ™  Block 1 II III  Bonny Best  Truss I ^7 64 51 T82  22 22  I II III  "6*8 28 25  I II III  "rpxBB)  25  I II IH_  IBBXPJ  Analysis of variance. Source D.g. Total 47 Varieties 3 Blocks 2 Trusses 3 Var.xBlock 6 Var.xTruss 9 Block xTruss 6 Error 18  II III IV Totals 4 1 3 ^ 4 2 m 44 28 44 180 32 3°l 22 l | i 117 103 125 527 "23 22 31 21. 22  25 27 22 74  "25"  24 25 _23_ 72  24 28 2  "80  27  33 26  22 27  19 23  22  29  30 30  16 404  57 330  78 337  374  S »S • 47994T48 3,089.73 44.04 296.23 142.46 1,127.18 29.96 264.88  96  9^  102 91_ 289 103 111  30.  312  93 109 115 317 1445  Blocks  478 502 465 _  M.S. 1,629.91 22.02 98.74 23.74 125.24 4.99 14.71  Bartlett s test Variety 136.81 23,144.08 = 1,504.92 24,649 Puck 7.72 84.92 6,960.08 7,045 B. B. 7.45 82.00 8,112.00 8,194 (PxBB) 21.17 232.92 8,374.08 8,607 (BBxP) , [(44x1.16776)-11(2.13612+0.88762+0.87239+1.32580)] 2.3026= =(51.381-57.441)2.3026 = 13.95 1  y  =  Required X W ^ ]  = ' 7  81  - 30 Table II.Number of flower buds formed on first four trusses of Puck,Bonny Best,and their reciprocal hybrids grown at temperatures above 65°P. Variety Puck  Block I II III  Truss I 51 45 52. t 4 8  Bonny Best  (PxBB)  (BBxP)  -  II 35 23 19  77  i l 22 20 24  5^  l IY 19 24 31  Totals 127 112 126 —53^91 91  74  I II III  20 20 20 60  21 24 21  '66  25 23 22 70  25 24 25 74  I II III  22 20 A  19 24 18  24 23 23 70  24 24 29 76  2  66 61  I II III  23  26 2±  Analysis of variance. Source D.F. Total 47 Varieties 3 2 Blocks Trusses 3 6 Var.xBlock Var.xTruss 9 Block xTruss 6 Error 18  73 347  88  270 89 90 273 Blocks 396 89 102 395 iL„ _ i Q 5 _ 288 1196  19 24 23 21 27 28 21 25 27 61 76 78 265 282 302  S•S• 2,421."67 499.50 3.79 313.17 57.88 273.66 1, 97.21 176.46  M.S.  -  166.50 1.89 104.39 9.64 141.51 16.20 9.80  Bartlett's test f o r homogeneity of variance. Variance S. S. Variety 12,803 - 11,102.08 = 1 , 7 0 0 . 9 2 1 5 4 . 6 2 Puck 6,122 - 6,075.00 = 47.00 4.27 B.B. 6,301 - 6,210.75 = 90.25 8.20 (PxBB) 6,996 - 6,912.00 = 84.00 7.63 (BBxP) X  i = [(44x0.99136)-11(2.18929+0.63063+0.9H03+0.88287)] 2.3026= = (43.619-50.785)2.3026 = 16.50.  Required^  =7.81  - 31 -  Table III.Logarithm transformation of data i n table I. Variety Puck  Block Truss I IU82607 II 1.80618 III 1.70757 5.33982  B.B.  IFXBBT  XBBXPT  II 1.61278 1.64345 1.50515 4.76138  Totals IV 1 .62325 " 6.61840 1.64345 6.54024 1.59106 - 6 39484 1.59106 4.59452 T.85776 19.55348 III 1.55630 1.44716  f  1.34242 1.39794 1.34242 1.43136 1.38021 .1.34242 4.66505 4.17172  1.41697 1.49136 1.36173 4.26806  1.36173 1.34242 1.54242 4.04657  5.51706 5.60756 5.42678 16755140  ^1.44716' 1.38021 I 1.39794 1.39794 II JUI6112 III h m 4.24304 4.13988  1.38021 1.44716 1.38021 4.20758  1.43136 1.51851 1.41497 4.36454  5.63894 5.76155 5*55485  I II III  I II III  1.34242 1.27875 1.34242 1.43136 1.36173 1.46240 1.43156 1.43136 4.20514 4753842"" 4.23618 17.85305 17.11140 17.30634  Analysis of variance.. S•S• P.P. SGurce 6.7138$ Total 47 0.47270 Varieties 3 0.00799 Blots 2 0.03256 Trusses 3 0.02741 Var.xB&ock 6 0.12148 Var.xTruss 9 0.00350 Block xTruss 6 0.48320 Error 18 Bartlett's test for Variety " Puck 31 .99523 B.B. 22.85337 (PxBB) 23.97730 (BBxP) 24.11875 -  16.95534  5.44071 1.47712 1.47712 5.73261 1.55630 5.81696 4.5105 4 16.99028 17.77971 70.05050 x._  0.15756 0.00399 0.01085 0.00456 0.01349 0.00058 0.00268  21.76  3.01  *  3.32  3.01  *  1.70 5.03 0.21  -  2.66 n.s, 2.46 * 2.66 n.s,  homogeneity of variance. Variance 3.S _„ 0.0T215 3I.86T54 = 0.13369 0.00220 22.82907 = 0.o2430 23.95696 = 0.02034 0.00184 24.05580 = 0.06295 0.00572 X - =[(44x0.428l3)-11(0.08468+0.34420+0.26694+0.75762)] 2.3026= = (18.83772 - 15.98784)2.3026 = 6,56 s  Re quired  =7.81  w  i  Table IV.Logarithm transformation of data i n table I I , Variety Puck  Block TrussI I 1 70757 1 .65321 II 1.71600 III 5*07578  B.B •  (fxBB)  Totals III IV II 5.87281 1.54407 1.34242 1.27875 1.36173 1.30103 1 .38021 5.69618 5.86652 IU27_815_ X..5.8021 1.49136 4.18455~4T02555 47T503217.43531  I II III  5.41913 1.30103 1 . 3 2 2 2 2 1.39794 1.39794 5.42318 1.36173 1.38021 1.30103 1.38021 . _ 5 ^3_6-3_6_l 1.34242 J..39794 1.50103 1.32222 16720592 4.17609 "4.0246T""4.10209 3.90309  T  1.34242 1.30103  II  1.27875 T738021 1.38021 1 . 3 6 1 7 3 U2S&2JL  4.02366  I II III  3.9H23  T736T7T  1.27875  1.32222  1.41497 1.38021 1 . 5 2 2 2 2 4.15691 3 . 9 2 3 1 9 17.16044 1 6 . 0 4 6 6 2 Analysis of Variance. S. S. Source 0.46026 47 Total 0.08193 3 Varieties 0.00085 2 Blocks 0.05628 3 Trusses 0.01850 6 Var.xBloek 0.22695 Var.xTruss 9 0.02856 Block xTruss 6 0.05316 18 Error  4.10367  1 .38021 5.38159 5.40470 1.36173 Lt4624iL_ 4.20434 1 6 . 2 4 5 9 0  5.38242 1.36173 5.61571 1.44716 1 . 4 5 1 5 6 . _ 5.5517I 4.20951 4.24025 1 6 . 5 2 9 8 6 16.43893 16.77100 6 6 . 4 1 6 9 9 1.38021 1.43136  h m  M.S. 0.02731  0.00042 0.01876 0.00208 0.02521  0.00476 0.00295  Bartlett's test for homogeneity of variance Variance S . S. Variety "07027fcT~ Puck 25.63130 - 25.33250 = 0.29880 0.00160 B.B. 21.90363 - 21.88598 = 0.01765 0.00300 (PxBB) 22.02713 - 21.99410 = 0.03302 0.00262 (BBxP) 22.79854 - 22.76968 = 0.02885 X* = [(44x0.47e26)-1l(0.43398+0.20520+0.47741+0.41863)] 2.3026= = (20.69144 - 16.88742)2.3026 = 8.75 0 = 1,037 X = 8.75/1.037 = 8.44 J  R e q u i r e d x ^ . ^ = 7.81  *  -  The  33  -  separate analyses f o r each temperature range are  g i v e n i n t a b l e s V and V I I I . Table V.Number of f l o w e r buds formed on f i r s t f o u r t r u s s e s of Bonny Best and i t s r e c i p r o c a l h y b r i d s w i t h Puck,at temperatures below 65°P. VarietyBlock Bbnny B. i ™ II III  Truss I "" 22 22 ?A. 68  II 25 27 22 74  III_IV 26 23 31 22 21. 22__ 80 ^ 7  TPxBB)"  ~~  24 25 72  24 28 24 76  19 23  22 29  (BBxP)  I 11 III  I II III  28 25 25_ 78 22 27  7 6 ^ 67 222 213  A n a l y s i s of v a r i a n c e . D.F. Source 35 Total 2 Varieties Trusses 3 2 Blocks 6 Var.x Truss Var.x B l o c k 4 6 Truss x B l o c k 12 Remainder  Totals, 96 102 9i 289 103 111  27 33 26 86  312  30 30  78 " W 234 249  S. S.  437.00 37,16  81.00  38.00  137.50 63.34 28.66 5 U 3 4  ~~  mTs  .  18.58  27.00 19.00 22,91  15.83  31ocks '292 J322  " 93 109 115_ 317 918  J?JM  "~  1.17 5.60  6.94 4.76  n.s, *  5.35  3.00 3.26 3.00  * * n.s,  -  3.70  4.77  1.11  4.27  —  Table V shows a) t h a t d i f f e r e n c e s between Bonny Best the r e c i p r o c a l s can be considered  due to chance,b) t h a t d i f f e r e n -  ces between t r u s s e s were r e a l , a n d c) t h a t there were  signifi-  cant d i f f e r e n c e s i n the i n t e r a c t i o n s of v a r i e t y x t r u s s v a r i e t y x block.  and  and  Table V I .  34  Comparisons between primary t r u s s e f f e c t s .  Truss I 222 3 -1 -1 -1  IJ "213 -1 3 -1 -1  III 234 -1 -1 3 -1  Required I> 5$ =  IV 249 -1 -1 -1 3  D « s> «  _  -?0T /I2x3x3 -66 f '/108 - I 8 r /108 +78)* /108  _ ______ JB\ = 8.3? 1.95 -40.3? 9.42 = 3.00 0.70 =56,34 13.19  n.s, * n.s, *  4. 75  Table VI shows the primary e f f e c t s of t r u s s e s . of f l o w e r buds formed on second t r u s s e s was  The number  s i g n i f i c a n t l y lower  t h a n the average number of f l o w e r s formed on o t h e r t r u s s e s , the number of buds on f o u r t h t r u s s e s was I t was  amd  s i g n i f i c a n t l y higher.  r e c o g n i z e d that the t r u e primary t r u s s e f f e c t could be  l a r g e l y masked by the v a r i e t y r t r u s s  interaction.  T o t a l s f o r comparing the e f f e c t s of the  interaction  v a r i e t y x t r u s s were obtained by summing over the  blocks.  Comparisons of g e n e t i c i n t e r e s t are j i)  [BB+ (BBxP)] - [ 2 (PxBB)] ,  i i ) ?BB - [(PxBB)+( BBxP)] ,  i n which, i ) i s a t e s t f o r the d e t e c t i o n through Bonny Best cytoplasm, and h y b r i d s as compared to Bonny B e s t . table  of m a t e r n a l  inheritance  ii.) i s a t e s t f o r v i g o r of The  the  v a r i a n c e s are shown i n  VII.  Table V I I . Comparisons of the e f f e c t s of the v a r i e t y x t r u s s at temperatures below 65°P. BB  68_7_4 80 67 i T + 1 +f+1 +1 i i ) +2 +2 +2 +2 Required P 5$ =  interaction  (PxBBT (BBxP) variance 78. 72 76 86 _. 76 67 78 9 6 _ ^ -2 -2 -2""-5 +1 +1 +f"+T C-TBT= 4.~50  F f f .05" ns  -1 -1 -1 -1  8.44  a  4.75.  -1 -1 -1 -1  r  72  i  a  n  c  e  (,-_j>l)=36.12 72  *  - 35 The maternal e f f e c t was n o t s i g n i f i c a n t as shown "by comp a r i s o n i ) . T h e P v a l u e f o r comparison i i ) i s s i g n i f i c a n t a t the 5$ l e v e l o f c o n f i d e n c e , t h e r e f o r e , d i f f e r e n c e s between the r e c i p r o c a l s and Bonny Best due t o the c o n d i t i o n of h e t e r o z y g o s i t y were t r u e ones.Thus d i f f e r e n c e s between Bonny Best and t h e h y b r i d s i n d i f f e r e n t t r u s s e s were s i g n i f i c a n t i n favour of the h y b r i d s . The a n a l y s i s of the data obtained from Bonny Best and the r e c i p r o c a l s , a n d e x c l u d i n g Puck,at temperatures above 65°P.is given i n t a b l e VIII,and none of the d i f f e r e n c e s was  signi-  ficant . Table V I I I . Number of f l o w e r buds formed on f i r s t t r u s s e s of Bonny Best and i t s r e c i p r o c a l s w i t h Puck,at temperatures above 6 5° P. Variety Block Bonny Best I II III ~~ "I" " II III  Truss I 20 20 21 60 22 20 24  - 56  _II _ I I I . _IV__ Totals. 21 25 25 91 24 23 24 91 _21_22__25_ 8 8 _ 66 70 74 270 19 24 18 6T  "24 23 22  70 -  3xPT  "  I II III  " "23 26 24 73 199  24 23 29 f£  89 90 24 273  27  - - -- — 23 o~9 " 28 102  21_.,_25_  2j__27_~  19~"~~24  21 6? 188  76 216  78 228  288 831  -Bloclcs. 2.69 283 _2ia__  -  36  -  A n a l y s i s of v a r i a n c e . Source D.F. S. S. 35 Total """236775" ' 2• 15.50 Varieties Trusses 3 104.97 2 8.66 Blocks 6 28.94 Var.x Truss 17.84 Var.x B l o c k 4 6 Truss x B l o c k 29.12 Remainder 12 31.72  ,  jMxSTZLZ f__  53l.  7.75 34.99 4.33 4.82 4.46 4.85 2.54  1.09 4.66  6.94 4.76  xxs» ns.  1.82 1.68 1.83  3.00 3.26 3.00  ns. ns. ns.  -  -  .  —  _  ~  Since temperature ranges c o n s t i t u t e d main t r e a tments i n t h i s i n v e s t i g a t i o n i t seemed d e s i r a b l e t o combine obtained a t the two temperature ranges.  t h e data  However i t has been  shown t h a t the date o b t a i n e d from Puck cannot be i n c l u d e d i n a combined a n a l y s i s o f v a r i a n c e w i t h those from the other varieties.  T h e r e f o r e , t h e r e are two d i s t i n c t a n a l y s e s .  F u r t h e r l i m i t a t i o n s are i n t r o d u c e d by t h e f a c t t h a t t h e r e i s no b a s i s on which b l o c k s i n the two houses can be i d e n t i f i e d w i t h each o t h e r , thus an a n a l y s i s o f v a r i a n c e f o r Puck d a t a cannot separate a b l o c k x temperature i n t e r a c t i o n e f f e c t . Hence an o u t l i n e o f the a n a l y s i s f o r Puck data appears as follows: Source Temperature Trusses Blocks w i t h i n temperatures Temperature x Truss B l o c k x Truss w i t h i n temp.  ALsJ1 3 4 3 12  The a n a l y s i s of v a r i a n c e f o r Puck data at both temperat u r e s g i v e s s i g n i f i c a n t F v a l u e s f o r temperature and t r u s s primary e f f e c t s , as shown i n t a b l e I X .  - 37 Table I X . E f f e c t s o f temperature on f l o w e r bud f o r m a t i o n of Puck. Block  Temperature  Truss 1  1 II III  5 5 ° - 6 5 ° P.  II III  Totals  Source Total Temperatures Trusses Blocks w i t h i n temperatures. Temp.x Truss B l o c k x Truss w i t h i n temp.  64  1  3  39  39  103  51 51 45 52 148 330  35 35 23 19 77 194  22 22 20 24 66" 169  186  180 161 527  125  19  127  24 J5_i _.  112 126  ~ 7 4 "  " ' 3 6 5 '  199  892  M.S.. _  4,299.34  23  42 44  117  32  S. S.  D.F.  28  51 182  Totals  4  3  41 44  67  •  I I  65°-75°P.  2  p  1,093.50 2,630.34  1,093.50 876.78  24.60  120.34 27.50  30.08  0.84  9.16  0.25  427.66  35.63  4  3 12  30.69  E v i d e n t l y , the e f f e c t s o f lower temperatures  4.75  *  3.49  *  3.26 n s . 3.49 n s .  -  produced  a marked i n c r e a s e i n t h e number o f f l o w e r buds p e r c l u s t e r formed on Puck, and the number of f l o w e r buds was s i g n i f i cantly higher i n f i r s t  trusses.  The data of the t h r e e remaining v a r i e t i e s can be combined i n a s i n g l e a n a l y s i s o f v a r i a n c e , as i t i s shown by an E t e s t o f the e r r o r mean squares c a l c u l a t e d i n t a b l e s V and VIII. P =  4.27  =  1.68  2.54  Required E  (  1  2  d > f  ,.  5 / o )  - 2.6  9  ns.  -  38 -  No b l o c k terms need t o be c o n s i d e r e d i n the combined analysis.  I f the combined e r r o r term i s c a l c u l a t e d as the  average of the two separate e r r o r terms from the two experiments, these e r r o r terms h a v i n g been reduced a l r e a d y by the s u b t r a c t i o n of the r e s p e c t i v e b l o c k terms, no f u r t h e r r e f e r e n c e t o b l o c k s i s necessary ( 7 ) . Table X. E f f e c t s of temperature on f l o w e r bud f o r m a t i o n o f Bonny Best and i t s F1 r e c i p r o c a l h y b r i d s w i t h Puck. Temperature 55°-65°F.  65°-75°B.  Truss  Var. B.B. PxBB BBxP  1 2 3 4  •1 2 3  68  ~ 7 8  74 80  72 76 86  289  312  o7...  60  66 70  270 559 Analysis of variance. Source D»P».„. Varieties 2 Trusses 3 Temperatures 1 Var.x Truss 6 Var.x Temp, 2 Truss x Temp. 3 Pooled e r r o r 24  _ jLiL?,.44•3? 184.48 105.12 106.22 8,33 1 .48  76 67 78 96 317  66 61 70  61 76  273 585  288 605  76  73  M,S«  Totals 222""  213 234 918  199 188  216  228 ^831 1,749  I  105.12  29«86  4.16 0.49 3.52  1.18 0,13  Trusses 421 401 450  _J2M 4,26  *  3.40 ns, 3.01 ns.  Table X shows t h a t t h e r e was a g e n e r a l s i g n i f i c a n t i n c r e a s e i n the number of buds p e r ' i n f l o r e s c e n c e on Bonny  39 Best and the r e c i p r o c a l h y b r i d s as the temperature goes down from the h i g h e r t o the lower l e v e l , b) E f f e c t s of temperature on c o m p a t i b i l i t y r e l a t i o n s h i p s . . Data c o l l e c t e d from the c o n t r o l l e d p o l l i n a t i o n e x p e r i ments are shown, i n t a b l e s XI and X I I f o r the c o o l and the warm rooms r e s p e c t i v e l y .  These data r e p r e s e n t the number  of f r u i t s s e t on each p l o t expressed as percentages of the number o f p o l l i n a t e d f l o w e r s .  The a n g u l a r t r a n s f o r m a t i o n  was used t o analyse the d a t a as shown i n the t a b l e s under the heading " a n g l e " .  - 40 Table X I . Number o f seeded f r u i t s s e t a t temperatures below 65°P.expressed as percentages o f the number of p o l l i n a t i o n s made,and c o r r e s p o n d i n g v a l u e s o b t a i n e d by means of t h e angular transformation. Treatment m PxBB Px(PxBB) Px(BBxP) BBS  BBxP BBx(PxBB) BBx(BBxP) (PxBB)a (PxBB)x? (PXBB)XBB  (PxBB)x(BBxP) ;BBXP}8  BBxPjxP  Rep.I $ angles. 3 8 . 2 3  38.2  57.89  49.5 50.2  59.09  Rep.II Rep.IlT jo angle _ _| angle _ T o t a l s 35.29 ' 3oTT" 50.00'""45.0" "119.7 ' 15.00 22.8 17.39 24.7 97.0 45.00 42.1 5 7 . 1 4 4 9 . 1 141*4 24.3  31.81 20.00  55.55 0 6 . (>0  48,2  111.4  0.0  60.3  39.39  38.9  30.76  33.7  38.88  38.6  18.75 2 5 . 6  31.25  23.52  29.0  3 3 . 3 3  26.66  25.00  30.0  0.00  50.00 70.00  45.0  46.15  42.8  29.41  56.8  3 3 . 3 3  35.2  44.44  60.00  54.8  41.8 57.2  66.66 5 4 . 8 66.66 5 4 . 8  38.0  40.90  66.66 50.00 50.00  45.0  45.0  26.6 35.2  0 . 0 0  70.72 37.93  6 3 . 1 5 5 2 . 6 37.50  ,BBxP)xBB 6 9 . 2 3 56.3 . BBxP) x (PxBB ) _^21^&±^_66jl6  37.8  98.2  31.1 30.0 32.8 50.8  95.3 60.0 120.6 142.8 151.4  157.0  39.8  122.8  4 6 . 1 5 42.8  133.3  45.0 52.14 4 6 . 2 147.5 L J i A i . y i . 4 2 ^ 1 _ J M  50.00  6§8.8  Analysis of variance Source D.E. S•S• 7 ,500.71""' Total 47 2 555.14 Blocks Treatments 4 ,405.56 15 2 ,540.01 30 Error  25.00  34.0  565.7  526.2  1890.7  ~"M7sr  -  277.57 293.70  3.27 3.46  3.32 2.04  n.s. *  84.66  I n t a b l e X I i t i s seen t h a t there were s i g n i f i c a n t d i f f e r e n c e s among t r e a t m e n t s . B l o c k primary e f f e c t s were nonsignificant. S i m i l a r i n f e r e n c e s can be drawn from the a n a l y s i s of var i a n c e o f t h e data i n t a b l e X I I .  - 41 Table X I I . Number o f f r u i t s s e t a t temperatures above 65° F. expressed as percentages o f the number o f p o l l i n a t i o n s made, and c o r r e s p o n d i n g v a l u e s o b t a i n e d by means of the a n g u l a r transformation. Treatment.. Pft PxBB Px(PxBB) Px(BBxP) BP® BBxP BBx(PxBB) BBx(BBxP) ;PxBB)a • .PxBB)xP PxBB)xBB ;PxBB)x(BBxP) BBxP)a .BBxP)xP BBxP)xBB .BBxP)x(PxBB) k  Rep.I Rep.II _ fo „angle Jo angle.. 40.00 3-9.2 "6'4.28 53."3 54.54 47.6 35.71 ^ 6 . 7 66*66 . 5 4 . 7 35.71 36.7 75.00 60.0 43.75 41.4 69.23 56.3 72,72 58.5 27.27 31.5 60.00 50.8 27.27 31.5 46.15 4 2 . 8 44.44 4 1 . 8 50.00 45,0 60.00 50.8 70.00 56.8 61.53 5 1 . 6 44.44 4 1 . 8 54.50 4 7 . 6 62,50 52.2 64,28 53.3 90.00 71.6 66.66 5 4 . 7 66,66 54.7 53.84 47.2 75,00 60 0 80.00 63,4 92.85 74.4 61 .55 51.6 75.35 58.9 782.8 ~~ 83576  Analysis of variance. „ Source " B.P. S^S. Total 47 4,721.22 Blocks 2 133.88 Treatments 15 2,625.57 Error 30 1,961.77  Rep.Ill f? ,__„an£le_ 50.00 '4576 56.25 4 8 . 6 52.94 46.7 70.00 56.8 57.14 49.1 58.3? 49.8 54.54 4 7 . 6 54.54 4 7 . 6 6 1 . 1 1 51.4 85.71 67.8 78.57 62.4 83.33 65.9 44.44 41.8 50 00 45 0 92.85 74.4 46.15 42.8 842.7  M.S. _ f 66.94 * 1.02 175.03 2.67 65.39  .._  "5$?  3.32 2.04  Totals 13775*" 132.9 1?8.1 158.? 163.9 132.1 121.9 134.4 159.0 161.2 162.2 190.8 151.2 152.2 212.2 15^3. 246*1.1  ....  _____  n.s.  I n o r d e r t o combine the two s e t s o f data i n one a n a l y s i s which would show the e f f e c t s o f temperature treatments,an P t e s t o f the e r r o r mean squares o f the two experiments was computed as g i v e n below. P = 84.66 = 1 . 2 9 n.s. 6 5 . 3 9  Required P 5 $ = 1 . 8 4 The n o n - s i g n i f i c a n t P v a l u e j u s t i f i e d the combination o f data as shown i n t a b l e X I I I .  - 42 Table X I I I . Angular v a l u e s o f f r u i t s e t t i n g a t low (11) and h i g h ( T 2 ) temperatures. Treatment _  _  11 '  T2.  - 3 8 . 2 3 9 . 2 "  PxBB 49.5 Px(PxBB) 50,2 Px(BBxP) 38.9 BB& BBxP 38.6 BBx(PxBB) 29.0 BBx(BBxP) 30.0 (PxBB)S 45.0 (PxBB)xP 56.8 (PxBB)xBB 54.8 PxBB)x(BBxP) 45.0 BBxP)® 45.0 BBxPjxP 52.6 BBxPjxBB 56.3 BBxP)x(PxBB) .^_____2  60  3£  £o__al__,  45.0  45.0  47.6  22.8  36.7  229.9  42.1 24.3  36.7  24.7 49.1 ,  48.6  54.7  46.7  279.5  48.2  56.8  269.6  60.0  41.4  257.2  224.2 31.5 25.6 50.8 34.0 49.8 230.3 31.5 35.2 42.8 31.1 47.5 217.2 41.8 0.0 45.0 30.0 47.6 194.4 50.8 42.8 5 6 . 8 3 2 . 8 51.4 279.6 51.6 35.2 41,8 5 0 . 8 6 7 . 8 304.0 47.6 41.8 5 2 . 2 54.8 6 2 . 4 313.6 53.3 57.2 71.6 54.8 65.9 347.8 54.7 38.0 54.7 39.8 41.8 274.0 4 7 . 2 3 7 . 8 60.0 42.8 45.0 285.4 63.4 45.0 74.4 4 6 . 2 74.4 359.7 51___6 5 4 . 8 5 8 . 9 _.4_2.1 4 . 2 . 8 . ___..285___A -^".8 56T.7 8 3 5 . 6 ' 6 2 6 7 2 " 842,7~"~ 4351.8 _  Source""' "3)717"~ H s . S . Total 95 15,611.05 Temperatures 1 3,389.13 Treatments 15 5,285.73 Temp.x T r e a t . 15 1,745.39 error  ..._Tt_._  53.3  Analysis ofjvarianjse.  Pooled  T1_. _ J | £ "36.5  -  M7S7''' 7" "g ~ 5$$ _~ " 7 7 " 3,389.13 17.70 3.39 * 352.38 1.84 1.84* 116.35 1.55 1.82 n.s. 75.02  I n t a b l e X I I I the P v a l u e s f o r temperature and treatment primary e f f e c t s were found t o be s i g n i f i c a n t when the t e s t term was t h e sum o f t h e average e r r o r term of t h e two e x p e r i ments and the mean.square of the temperature x treatment i n t e r a c t i o n , a f t e r t h i s l a t t e r was shown t o be non-significant.How-  ever , i f the t e s t i n g term had been c a l c u l a t e d as the pooled mean square of the b l o c k primary e f f e c t s and o f a l l i n t e r a c t i o n s i n which b l o c k s take p a r t , t h e P v a l u e s would have been only s l i g h t l y changed,and c o n c l u s i o n s would have been the same. Such p o o l i n g would have bg,en necessary s i n c e there i s no b a s i s  -  43 -  on which r e p l i c a t e s can he i d e n t i f i e d . The f o l l o w i n g s e t s o f comparisons between treatments were made s 1) a l l treatments were compared t o P a , 2) a l l treatments were compared t o BBa, 3) c r o s s - p o l l i n a t i o n s were compared t o s e l l i n g s w i t h i n each variety. Among the r e s u l t i n g 35 comparisons w i t h i n t a b l e X I I I , e l e v e n showed s i g n i f i c a n t d i f f e r e n c e s , a n d are l i s t e d below, w i t h d i f f e r e n c e s and mean square?. PS - BBx(BBxP) P® - (PxBB)x(BBxP) m - (BBxP)xBB  = +62.8 - -90.6 =-102.5  328.65 684.03 875.52  BB& BB& BB& BBS BB& BB&  - (PxBB)xP - (PxBB)xBB - (PxBB)x(BBxP) - (BBxP)xP - (BBxP)XBB - (BBxP)x(PxBB)  = -79.8 = -89.4 =-123.6 = -61.2 =-135.5 = -61.2  530.67 666.03 1273.08 312.12 1530.00 312.12  (PxBB)& - (PxBB)x(BBxP (BBxP)a - (BBxP)xBB  = -68.2 = -85.7  387.60 612.o4  Required v a r i a n c e a t the 5 $ l e v e l = 3 0 0 . 0 8 The above comparisons show a t the 5% l e v e l o f confidence t h a t ; a ) compared t o Pa,Bonny Best p l a n t s p o l l i n a t e d w i t h p o l l e n from the (BBxP) , gave the lowest f r u i t s e t . I n the same sfct of f  comparisons, (BBxP) i p o l l i n a t e d w i t h Bonny Best gave s i g n i f i F  c a n t l y h i g h e r f r u i t set,and so d i d t h e h y b r i d (PxBB) , when F  pollinated with i t s reciprocal. b) compared t o BBa,both h y b r i d s s e t a h i g h e r number o f f r u i t s when c r o s s - p o l l i n a t e d than when s e l f - p o l l i n a t e d .  - 44  -  c) i n comparisons of treatments w i t h i n each v a r i e t y , i ) (PxBB)- had h e a v i e r f r u i t s e t when c r o s s - p o l l i n a t e d w i t h i t s r e c i p r o c a l , a n d I i ) (BBxP) , when c r o s s e d w i t h Bonny B e s t . F  A t h i g h temperatures a l l f r u i t s produced c o n t a i n e d seeds. A t low temperatures p a r t h e n o c a r p i c f r u i t s o c c u r r e d as shown i n t a b l e XIV. Table XIV. Number of p o l l i n a t e d f l o w e r s , t o t a l of f r u i t s e t , number of p a r t h e n o c a r p i c f r u i t s , a n d percentages of parthenocarpy o c c u r r i n g on the f o u r tomato l i n e s a t low temperatures. Variety Puck Bonny Best (PxBB) (BBxP)  No, of p o l linations 290 199 223 237  Nbuof f r u i t s set 119 67 129 121  No,of partheno- fo of parc a r p i c f r u i t s t heno c amy 0 0 19 28.35 7 5.42 5 4.13  P a r t h e n o c a r p i c f r u i t s d i d not develop on Puck p l a n t s independently of the source of p o l l e n used i n the c o n t r o l l e d p o l l i n a t i o n s , w h e r e a s Bonny Best bore the h i g h e s t number of parthenocarpic f r u i t s .  c) E f f e c t s of seed set on e a r l i n e s s of •fruits. The data r e l a t i n g the number of seeds per f r u i t t o the number of days o c c u r r i n g between p o l l i n a t i o n and m a t u r a t i o n as seen i n t a b l e XV were s u b j e c t e d to a n a l y s i s of c o v a r i a n c e , as shown i n t a b l e X V I , i n o r d e r to a s c e r t a i n the extent to which e a r l i n e s s may be dependent upon e f f e c t i v e p o l l i n a t i o n and subsequent seed development.The data were obtained i n the warm house,and y i e l d e d a c o r r e l a t i o n c o e f f i c i e n t , r = -0.457-  - 45 measuring  the c l o s e n e s s of the c o r r e l a t i o n between the two  v a r i a b l e s . T h e negative, value of the c o e f f i c i e n t i s due to the v a r i a b l e s being i n v e r s e l y r e l a t e d . R e g r e s s i o n c o e f f i c i e n t s were c a l c u l a t e d and t h e i r values found as f o l l o w s : 1)  b  y  >  x  = -0.048  2) *x.y = -4-275 Negative v a l u e s i n d i c a t e t h a t the slope of the regression l i n e s was downward.Coefficient  1)measured, the average decrease i n  day u n i t s i n the m a t u r a t i o n p e r i o d corresponding to an i n c r e a se of one seed i n f r u i t content.Under  the c o n d i t i o n s of the ex-  periment such a decrease had an o v e r a l l average value f o r the f o u r v a r i e t i e s of -0.048 days per s e e d . C o e f f i c i e n t 2) was measure of the decrease i n seed content which can be  a  expected  f o r an i n c r e a s e of one day i n the l e n g t h of the m a t u r a t i o n period. Regression c o e f f i c i e n t s b  were c a l c u l a t e d f o r each  y .x v a r i e t y and are g i v e n as f o l l o w s : Puck = -0.024 Bonny Best  = -0.082  (PXBB)FI  = -0.075  (BBxP)n  = -0.034  These v a l u e s show t h a t e a r l i n e s s was much more dependent on seed content i n Bonny Best,than i n the other v a r i e t i e s . H o w ever, because of v a r i e t a l d i f f e r e n c e s i n average seed contents per f r u i t , a s w e l l as of d i f f e r e n t values of r e g r e s s i o n both parents matured f r u i t s e a r l i e r than the hybrids.The average  _ 46 -  l e n g t h o f the m a t u r a t i o n p e r i o d f o r each v a r i e t y was found t o he as f o l l o w s : Puck = 67;Bonny Best = 71;(PxBB) = 76; (BBxP) , = 74. days. n  F  Table XV. Number of seeds p e r f r u i t , a n d number of days t o mat u r i t y i n each of the f o u r tomato l i n e s a t temperatures above 65°P. Puck Seeds .Pays  ~1$8~' 63 72  66  52  64 64 64  17 70 80 23 92  107 126 98 45 40 159 104 151 182 154  67  87  61 66 62 66 76 68 67 67 67 72  TPX": B»B» Ft Seeds .Days Seeds Bays 153 6*8 " 279' """6'q 194 70 67 123 208 64 71 148 175 77 76 132 143 70 74 102 2? 76 62 271 165 81 68 140 227 76 61 87 217 74 83 35 161 66 83 43 65 64 171 194 73 125 64 103 79 68 106 156 94 71 67 77 68 111 96 83 95 29  70 75 63 _11_L T o t a l s 2049 1355 '1796"" T Q S T ' 2458''" f 197" 71.2 153.6 74.I Means 102.4 6 7 . 7 119.7 166  CBBXPX-,  Seeds Days 144' ' 70" 105 74 20 74 284 73 207 75 185 77 86 67 40 76 59 71 30 71 55 79 40 77 115 79 58 82 31 73 237 66 308 64 64 96 72 2303 "1408"" 121.2 74.1  Table XVI. A n a l y s i s of covariance of data from t a b l e XV, Source" I). P. , SSx Total 69" " 350,741 .78 Varieties 3 23,672.98 Within Var. 66 327,068.80  Spxy -12,923.62 3,088.60 -16,012.22  R e g r e s s i o n and c o r r e l a t i o n c o e f f i c i e n t s . by. b  x  = -0.048  x . y = -4.275  r  = -0.457 x.y  _  SSy 4,323.28 578.36 3,744.92  - 47 C a l c u l a t i o n o f a d j u s t e d v a r i e t y means. Experiment mean = x = 124.50 Var. Puck" B.B. (PxBB) (BBxP) ,  X 102.45 119.73 153.62 121 .21  f/  F  X-x ^22T05 - 4.77 29.19 3.29  b(X-x) -U05" -0,02 1 .39 0.15  y adj.y 67". 75~~'66~.W 71 .26 71 .24 74.81 76.20 74.10 74.25  A n a l y s i s of c o v a r i a n c e f o r each v a r i e t y . . V&r,__ D.F. 19 Puck 14 B.B. (PxBB) , 15 18 (BBxP) F  f(  Puck  h  B.B.  b  (PxBB)  P(  (BBxP)*  SSx ' 51 ,070.95" 45,360.94 76,595.75 154,041.16  SSy •1 ,2 40.7 5 691 .75 •3,734.93 822.94 •5,648.12 1,260.44 •5,388.42 969.79  = -0.024  = -0.082 y.x = -0.073 y.x ^y .x = -0.034  b  B. 0ytologic_al Exp eriment s. a) M i c r o s p o r o g e n e s i s . M e i o s i s does not occur s i m u l t a n e o u s l y i n a l l p o l l e n mot h e r c e l l s o f an anther.Metaphase,anaphase,and telophase o f the homotypic d i v i s i o n o f t e n are contemporaneously t a k i n g p l a c e i n m a t e r i a l d i v i d i n g under normal temperature conditio The most o u t s t a n d i n g d e v i a t i o n from the p a t t e r n s of re l a r m e i o s i s observed i n microsporogenesis under low tempera' t u r e s was a g r e a t e r spread of the meiotic/bhases o c c u r r i n g a  - 48 any one time w i t h i n the same a n t h e r . I t was noted t h a t some of the  p o l l e n mother c e l l s undergoing m e i o s i s i n the lower tempe-  r a t u r e range were delayed to a g r e a t e r extent than under more customary c o n d i t i o n s of temperature.Thus,in m a t e r i a l of the same anther,chromosomes of c e l l s s t i l l i n e a r l y telophase I I were seen a l o n g w i t h p o l l e n t e t r a d s i n which m e i o s i s had a l ready heen completed,and m a t u r a t i o n of p o l l e n had p r o g r e s s e d , as shown hy the r e d c o l o r a t i o n of acetocarmine s t a i n i n g of the  walls. During the e x p e r i m e n t s , d i u r n a l temperature f l u c t u a t i o n s  were kept as c l o s e l y as p o s s i b l e w i t h i n a 10°F range,the maximum  o c c u r r i n g i n the noon h o u r s , e s p e c i a l l y i n sunny days,Thus,  i n the c o o l house temperatures were n o r m a l l y below 60°P.and went over 60°P. o n l y a few hours on some days. I t i s known t h a t temperature has d i f f e r e n t e f f e c t s on d i f f e r e n t m e i o t i c stages,though more i s known about e f f e c t s of h i g h than of low temperatures,Observations made on the v a r i e t i e s used i n t h i s experiment supported the h y p o t h e s i s of d i f f e r e n t temperature requirements of m e i o t i c phases.Prob a b l y p o l l e n mother c e l l s which reached the stages r e q u i r i n g the h i g h e s t temperatures of the 55-65" P. range a f t e r the noon hours, were delayed u n t i l minimum temperatures r e q u i r e d f o r the process were a t t a i n e d a g a i n i n the f o l l o w i n g d i u r n a l f l u c t u a t i o n . I n the meantime,cells i n which m e i o s i s had progressed beyond the s e n s i t i v e stages were able to complete t h e i r d i v i s i o n , i n c r e a s i n g the gap o c c u r r i n g between e a r l y and l a t e f o r -  - 49 -  mine; t e t r a d s . Such a p a t t e r n nrobably r e s u l t s i n enhanced c o m p e t i t i v e e f f e c t s when s t a r c h synth«si s i n the maturing microspores  ±s l i m i t e d by short carbohydrate  I n g e n e r a l , low temperatures  product  "tuTvol i e s .  onlv a r e l a t i v e l y  low increa.se o f abnormal d i v i s i o n s , and the occurrence o f abn o r m a l i t i e s was not great enough t o e x p l a i n the h i g h r a t e o f p o l l e n degeneration. The most evident abnormality was the f o r m a t i o n of b r i d g e s at anaphase of the h e t e r o t y p i c d i v i s i o n .  I n one i n s t a n c e a.  b r i d g e was seen between two of the f o u r n u c l e i o r i g i n a t i n g from the homoiypic  division,  Brid.ees are l i k e l y t o produce  gene d u p l i c a t i o n s and. d e f i c i e n c i e s , but evidence o f them wp.s not observed.  However, fragmentations and lagrdxur chromosomes  were r e l a t i v e l y frequent and r e a d i l y v i s i b l e .  I n one i n s t a n c e  a supranumerary s m a l l nucleus was noted, probably  formed from  l a g g i n g chromosomes. I r r e g u l a r p a i r i n g a t nropha.se I o f t e n r e s u l t e d i n format i o n of s i s t e r n u c l e i c o n t a i n i n g reduced or supranumerary chromosomes.  The tomato i s s e n s i t i v e t o the e f f e c t s o f chromo-  somal imbalance, and any abnormality may account f o r reduced pollen production. Because o f low frequency and of l a c k of c o n s i s t e n c y i n the occurrence o f a b n o r m a l i t i e s a t any one time, no attempt was made t o c a l c u l a t e t h e i r percentage  values.  - 50 b) P o l l e n v i a b i l i t y . V i a b i l i t y o f p o l l e n produced i n the warm house and e s t i mated by means o f the acetocarmine s t a i n i n g procedure i s g i ven i n t a b l e XVI. Table XVI. Percentages o f v i a b l e p o l l e n of Puck,Bonny B e s t , and t h e i r r e c i p r o c a l hybrids,formed, a t temperatures above 65°P. Bate December 11 13 15 19 21 23 25 27 29 31 January 2 4 6 8 10 12 14 16 18 20 24 26 Totals Means Range s  Puck "Too* 97 100 96 97 98 94 98 97 98 86 97 97 93 85 87 78 97 92 95 97  SOL—  2077 94.40 14  B.B. 83 95 86 47 78 88 83 84 96 75 91 92 87 85 85 94 90 88 96 96 95 96 ' 1"910 86.81 49  (PxBB)^ 98 98 96 96 92 98 92 88 93 94 98 99 91 95 93 97 92 79 98 92 99  (B3x?)._7  2076 98.85 20  2090 95.00 24  28____.  99 97 96 99 97 75 96 96 90 88 97 99 97 93 97 93 98 99 94 98 99 9_2-i-~,.  Percentages o f normal appearing p o l l e n were h i g h and c o n s i s t e n t l y so through the d u r a t i o n o f the whole experiment. I n g e n e r a l Bonny Best had lower percentages o f v i a b l e p o l l e n than Puck and both the hybrids,Bonny Best a l s o had the widerrange ,while the h y b r i d s averaged the h i g h e s t means of v i a b l e  - 51 pollen, produced a t the warm temperatures. The p o l l e n produced i n the c o o l house gave the data shown i n table XVII. Table X V I I . Percent o f v i a b l e p o l l e n o f Puck,Bonny Best,and t h e i r r e c i p r o c a l hybrids,formed a t temper a t u r e s below 65°P, Blower 1  2 3 4 5 6 7 8  9 10  Totals Means Ranges  B.B.  (PxBB) ,  (BBxP)-,  25 0  8 2 37 1 74  15 14 11 13  8 22  3 77 0  26 4 28 36 10 17 44 26 15  Puck 3 9 1  __  25  1  0  23 12  108 10.8  F  _  13 24  9  1  3  6 109 10.9 23  203 20.3 77  _______  229 22.9  40  I n g e n e r a l t h e percentages o f n o r m a l , v i a b l e p o l l e n were e x c e e d i n g l y low when compared t o the r e s u l t s f o r p o l l e n p r o duced a t t h e h i g h e r temperature  range.  Ranges i n v i a b i l i t y were g r e a t e r i n a l l v a r i e t i e s grown at low temperatures as compared t o r e s u l t s a t the h i g h e r temp e r a t u r e s .Means showed s t r i k i n g s i m i l a r i t i e s between.lines where maternal p a r e n t s were o f the same v a r i e t y , t h a t i s Puck and (PxBB) ,and Bonny Best and (BBxP) .These means were subf  fi  j e c t e d t o t t e s t s as f a l l o w s j x S.S. Var. Var.-  Puck 10.8 795o60 88.40 8,840  (PxBB) 10.9 394.90 43.87 4.387 r  SE_, =^1'5.227 = D t  Required t ( ii)  x  S.S.  Var.  Var.-r  l 8  d  =  0.1  3.63  =0.027  n.s.  3.63  .f,,. .) =  2.101  59  Bonny Best 20.3 8,732.10  1,282.90  970.23  142.54  97.023  14.254 SEg  = ~  111.277  2___6_  -  =  0.246  10,54 n.s.  T6.54 t v a l u e s are not s i g n i f i c a n t showing t h a t d i f f e r e n c e s between means of r e l a t e d v a r i e t i e s c o u l d have been due to chance, thus s u g g e s t i n g the p o s s i b i l i t y of t r a n s m i s s i o n i n maternal f a s h i o n o f the p r o d u c t i o n of p o l l e n at low temperatures. c) P o l l e n g e r m i n a t i o n experiments, Experiments on p o l l e n g e r m i n a t i o n j n j y i t r o  encountered  h i g h l y i n c o n s i s t e n t r e s u l t s , f o r which no reason was obvious. Such i n c o n s i s t e n c i e s occurred i n t e s t i n g p o l l e n produced i n the warm house. Data have been grouped i n t a b l e X V I I I , and the blank space corresponding t o the 20°C. m a t e r i a l on the f i r s t date was due t o l o s s of the m a t e r i a l because of i m p e r f e c t s e a l i n g of the w e l l - s l i d e s ,  - 53 i Table X V I I I . Percentages of p o l l e n g r a i n s produced at h i g h temperatures , germinated at 10°, 15°,,and 20° C. Temu Count I—..'. 10° G. 1 2 3 4 Ave. ~ 1 5° 0. 1 2 3 . 4 Ave. 20° C.  1 2 3 Ave.  Mar . 3 ™ ®eb°U""~Feb.l8 ~~ Fe¥.24~"" ~I?eb727 _P B < B i_ _ _P__ B • B_4_ P .B.B. P B..B. P B.B. 4 20 """"15 ~ ' 10 11 26 6 6 "20 7 6 34 10 11 6 23 4 11 21 10 19 29 14 18 12 25 2 • 7 20 9 a 28 9."5 28 ' 4 8 20.3 8.6" "8.1 ;?7T6"i'3~'~13~ 28 6 21 7 12 18 24 35 21 27 22 36 12 45 16 26 44 7 9 11 16 20 12 39 21 25 14 45 6 13 26 11 18.2 "27 T5~ 15 38.6 ~" 7."3 "1*2 "3976^1_T.3"~23~ 10 12  11 11  17 15  48 42  14  44  12  42  8 11  16 15  24  17 24 7 16 27 22 8.6" 15".6" 25.6" 21 26  15 18 24 19  By i n s p e c t i o n of t a b l e X V I I I extreme v a r i a b i l i t y i n trie average g e r m i n a t i o n percentages o b t a i n e d on d i f f e r e n t dates i s c l e a r l y noticeable.However,two t r e n d s emerge from these d a t a : a) there was an i n c r e a s e i n percentages of germinated p o l l e n w i t h i n c r e a s i n g temperatures.This i n c r e a s e o c c u r r e d i n a l l v a r i e t i e s and was p a r t i c u l a r l y marked, between the 10° and 1 5°C. levels. b) under the c o n d i t i o n s of t h i s experiments,at 10° and 15° G. puck p o l l e n produced a t h i g h temperatures averaged lower germ i n a t i o n percentages than Bonny Best d i d i n f o u r out of f i v e o c c a s i o n s ; a t the temperature of 20°C.each of the two  varieties  was the best i n two out of f o u r t r i a l s . On February 2 4 , d i f f e r e n c e s i n g e r m i n a t i o n percentges of the two v a r i e t i e s were at t h e i r maximum,Puck being at i t s best  - 54 Bonny Best a t i t s lowest v a l u e . E v i d e n t l y , i f the same e n v i r o n mental c o n d i t i o n s were a c t i n g on both v a r i e t i e s , t h e y were a f f e c t i n g Bonny Best t o a g r e a t e r extent than Puck.Since media and temperatures i n the experiments were c l o s e l y c o n t r o l l e d , any cause producing such i n c o n s i s t e n c y was thought t o be act i n g on the p o l l e n before samples were taken f o r g e r m i n a t i o n , t h a t i s i n the greenhouse where the p o l l e n was produced. The data c o l l e c t e d from o b s e r v a t i o n s on p h y s i o l o g i c a l age the p o l l e n a t . s a m p l i n g time are g i v e n i n t a b l e X I X . Table XIX. Percentages o f p o l l e n g e r m i n a t i o n from f l o w e r s a t d i f f e r e n t stages o f a n t h e s i s . Bate Anth. March 6 1  n  +  1  ^ ? 3 2  2  25  3 4  24 14  fi  22  2.5 23.5  20  22.0  16  15.0  5  March 7  March 15  r  liri+  ?  o n n  £ 7  B e S t  2 6  4.5 8.5 5.5  27  28  27.5  7  10  5 .  6  5  5.5  30  15 21 26  19.5 18.5 28.0  1 1 16  0 2 14  0.5 1.5 15.0  11 15 24 14  13 18 22 12  12.0 16.5 23.0 13.0  13 14 10 7  12 13 7 8  12,5 13.5 8.5 7.5  1 2 3  24  1 2 3 4  16  Percentages of g e r m i n a t i o n were c o n s i s t e n t l y h i g h e r f o r Puck p o l l e n taken from blossoms i n i n t e r m e d i a t e stages of ant h e s i s , and q u i c k l y d e c l i n e d on both s i d e s of the optimum.Bonny Best averaged v e r y low percentages i n two out of three t r i a l s , i n which h i g h e s t v a l u e s were found f o r p o l l e n taken from anthers i n the e a r l i e s t atage.On the t h i r d  date,however.  - 55 t h i s t r e n d was r e v e r s e d . These i n c o n s i s t e n c i e s give f u r t h e r support t o the hypot h e s i s t h a t presumably s i m i l a r environmental c o n d i t i o n s have d i f f e r e n t e f f e c t s on d e t e r i o r a t i o n o f Puck and Bonny Best p o l l e n , f o l l o w i n g dehiscence o f the a n t h e r s .  D u r i n g the experiments s t u d y i n g p o l l e n g e r m i n a t i o n i n v i t r o . i t was noted t h a t some p o l l e n g r a i n s produced two tubes i n s t e a d o f t h e n o r m a l l y o c c u r r i n g s i n g l e tube,as i l l u s t r a t e d i n p l a t e s I and I I . S u c h g r a i n s were seen v e r y i n f r e q u e n t l y , and attempts t o s t a i n the n u c l e i w i t h i n the growing tubes w i t h c r y s t a l v i o l e t f a i l e d i n a l l cases. On some occasions,when p o l l e n tubes from d i f f e r e n t g r a i n s were observed a t two hour, i n t e r v a l s , t w o o f them were seen growing toward each o t h e r a t f i r s t , t h e n meeting I n an o v a l enlargement,as seen i n p l a t e I I I , f r o m w h i c h , ! i n a l l y , a s i n g l e tube emerged,as seen i n p l a t e IV.Observations were repeated to a s c e r t a i n the occurrence o f anastomosis.However,even the use of a m i c r o m a n i p u l a t o r d i d not succeed i n i n c r e a s i n g the frequency of growing p o i n t s meeting a t the r i g h t stage,and when tubes m e t , f r e q u e n t l y one of the two b u r s t , o r they went ,onP under  the other.Nonetheless,by means of micromanipula-  t i o n s i t was p o s s i b l e t o a s c e r t a i n on s e v e r a l occasions what appeared t o be the f u s i o n o f the tubes,though no c o n c l u s i v e evidences t o support t h e occurrence., of complete anastomosis and the m i x i n g o f tube contents could be gathered,,  - 56 -  Plate I I - Pollen grain with two pollen tubes.  - 56 b -  Plate IV - Two pollen tubes appear to have merged and a single tube developed, suggesting fusion of pollen tubes.  - 57 DISCUSSION  The i n c r e a s e i n number of f l o w e r buds produced by exposures o f p l a n t s t o temperatures below the optimum range o f 6 5 ° to 7 5 " F. was found t o be s t a t i s t i c a l l y s i g n i f i c a n t , i n agreement w i t h l e w i s ' ( 2 9 ) and Daubeny s (11) r e s u l t s . T h e former r e p o r t e d 1  t h a t s i m i l a r e f f e c t s were o b t a i n e d i n experiments i n which s e e d l i n g s exposed t o temperatures o f 14"C. were compared t o s e e d l i n g s grown a t 25°C.In those experiments,aftex the t r e a t ments a t s e e d l i n g s t a g e , p l a n t s were presumably kept i n u n i f o r m environmental c o n d i t i o n s u n t i l f l o w e r buds were counted,Lewis concluded t h a t t h e s e n s i t i v e p e r i o d f o r temperature e f f e c t s showing up t o f i f t h c l u s t e r s occurs between the 8 t h day a f t e r emergence and the f o r m a t i o n o f the f i r s t  inflorescence.  However,in the present i n v e s t i g a t i o n s e e d l i n g s were kept i n a u n i f o r m environment u n t i l t r a n s p l a n t i n g time when f i r s t i n f l o r e s c e n c e s were a l r e a d y formed.Despite thjs u n i f o r m i t y o f i n i t i a l t r e a t m e n t s , l a t e r exposures to d i f f e r e n t i a l temperatures  produced e f f e c t s s i m i l a r t o those d e s c r i b e d i n Lewis'  report,showing t h a t the s e n s i t i v e temperature stages extend beyond the p e r i o d of f l o r a l i n d u c t i o n and i n i t i a t i o n , p o s s i b l y i n c l u d i n g the whole process of development  of the i n f l o r e s c e n c e  Furthermore,at the lower temperature range of 5 5 ° t o 65"F., i f f l o w e r bud counts were repeated at l o n g i n t e r v a l s on the same c l u s t e r s , i n c r e a s e d v a l u e s were f o u n d , p a r t i c u l a r l y where t h e r e was l i t t l e o r no f r u i t  setting.  These o b s e r v a t i o n s suggest t h a t temperatures below the  - 58 optimum range f o r tomato growing produce s i g n i f i c a n t i n the numbers of f l o w e r s p e r i n f l o r e s c e n c e , a n d peratures  increases  t h a t such tem-  are e f f e c t i v e a t any stage of development of the  inflorescence. The purpose o f the p o l l i n a t i o n experiments was t o g a i n knowledge on c o m p a t i b i l i t y r e l a t i o n s h i p s between the f o u r v a r i e t i e s under i n v e s t i g a t i o n , a n d t o a s c e r t a i n any nhange i n those r e l a t i o n s h i p s , s u s p e c t e d o f o c c u r r i n g under d i f f e r e n t i a l temperature  treatments.  I n p r e v i o u s work i t had been r e p o r t e d by Daubeny t h a t the a p p l i c a t i o n of Puck p o l l e n t o Bonny Best stigmas a t c o o l temp e r a t u r e s f a i l e d to f e r t i l i z e the ovules;the were found to be Largely parthenocarpic.Since  f r u i t s produced p o l l e n used was  produced i n the warm house and supposedly v i a b l e , t h e s e ings appear t o d e t r a c t from the e a r l i e r hypothesis  find-  t h a t gene-  t i c d i f f e r e n c e s i n p o l l e n v i a b i l i t y are the b a s i s f o r the d i f f e r e n c e s i n f r u i t s e t t i n g a t low temperatures. The present i n v e s t i g a t i o n was aimed a t s u b s t a n t i a t i n g these observations,and  extending them t o the P1 hybrids.Thus,  behaviour of p o l l e n produced i n the warm house by each v a r i e t y was observed on stigmas of a l l other v a r i e t i e s a t the two temperature  l e v e l s . E o attempt was marie t o use p o l l e n produced, a t  low temperatures s i n c e i n s u f f i c i e n t amounts are produced by Bonny Best under such c o n d i t i o n s . The  improvement of tecbnicmes f o r commercial  production  - 59 of P1 h y b r i d seed has proven i t s e l f to be a v a l u a b l e means of p r o v i d i n g growers w i t h the d e s i r e d s e e d , w h i l s t other timer e q u i r i n g programs are c a r r i e d out  simultaneously.However,  from the r e s u l t s of these experiments  i t appears t h a t PI hy-  brids,when s e l f e d produce s i g n i f i c a n t l y lower y i e l d s than i n c r o s s - p o l l i n a t i o n s w i t h other v a r i e t i e s . T h e tomato being a h i g h l y s e l f - p o l l i n a t e d crop,the use of (PxEB) , i s p o s s i b l y to F  be  avoided. The importance  of knowledge of c o m p a t i b i l i t y r e l a t i o n s h i p s  can be s t r e s s e d by i n f e r e n c e s drawn from, the r e g r e s s i o n analys e s . I t i s evident t h a t any cause producing a r e d u c t i o n i n seed content of tomatoes w i l l r e s u l t i n an i n c r e a s e of the number o f days necessary f o r f r u i t m a t u r a t i o n . When low s p r i n g temperatures  are the l i m i t i n g f a c t o r t o  the p r o d u c t i o n of e a r l y y i e l d s , f r u i t s w i t h poor seed w i l l be r e l a t i v e l y l a t e maturing even i f the f r u i t was  content set  e a r l y i n the season.Furthermore,varieties on which low temper a t u r e s are bound to produce parthenocarpy  or d r a s t i c  t i o n s i n number of seeds, appear to be u n s u i t e d to areas c h a r a c t e r i z e d by short seasons because low  reduc-  growing temperatures  are l i k e l y not o n l y to delay e a r l y y i e l d s , b u t a l s o to h i n d e r the m a t u r a t i o n of l a t e f r u i t s . Observations on parthenocarpy  confirmed previous r e p o r t s  on the frequency of occurrence of seedless f r u i t s on Bonny Best (11,17).However,percentages of parthenocarpic f r u i t s were  - 60 s m a l l e r than those found by other workers,probably owing t o a d i f f e r e n c e i n technique,whereby  p o l l e n a p p l i c a t i o n s were  repeated t w i c e a t one-day i n t e r v a l s . S u c h a technique d i d poss i b l y i n c r e a s e the percent of f r u i t s set,and from o b s e r v a t i o n of p l a n t s i t was p o s s i b l e to see t h a t i n g e n e r a l the development oflT seeded f r u . i t s had p r i o r i t y over p a r t h e n o c a r p i c f r u i t s , which o f t e n a b s c i s s e d as undeveloped  ovaries.  C y t o l o g i c a l Experiments. As a l r e a d y p o i n t e d out by Maheshwari (32) and by Hewlett (18),when carbohydrates are i n s h o r t supply d u r i n g the processes of p o l l e n maturation,more g r a i n s are bound to become  o r l e a s l a r g e amounts of p o l l e n  - o n - f u n c t i o n a l , o r i n extreme cases,  to degenerate a f t e r meiosis has been completed.Rates  of normal  m e i o s i s were not found t o be i n f l u e n c e d by low temperatures t o so great an extent as t o account f o r e x t e n s i v e p o l l e n degener a t i o n such as t h a t o c c u r r i n g i n Bonny Best a t low temperatures . Under the c o n d i t i o n s of t h i s experiment,shortage of carbohydrates might have been due t o low p h o t o s y n t h e s i s . G l a s s w a l l s of the greenhouse cut down l i g h t  considerably,particularly  d u r i n g p e r i o d s o f d u l l weather i n wintertime,and the a r t i f i c i a l i l l u m i n a t i o n p r o v i d i n g l i g h t of low energy was probably o n l y e f f e c t i v e on upper leaves,because the lower ones were l e f t i n the shade,In addition,temperature might have been a c t i n g as a l i m i t i n g f a c t o r when l i g h t was s u f f i c i e n t , t h u s r e d u c i n g the r a t e of p h o t o s y n t h e s i s , o r producing narrow r e s -  - 61 piration/photosynthexic  ratios.Whatever the cause of carbohy-  d r a t e shortage,the occurrence of some p o l l e n mother c e l l s comp l e t i n g meiosis  c o n s i d e r a b l y e a r l i e r than others would give  e a r l i e r forming t e t r a d s an. advantage  in nutritional  the  competition  w i t h r e s p e c t to l a t e forming ones. As a p o s s i b l e a l t e r n a t e e x p l a n a t i o n to p a r t i a l p o l l e n deg e n e r a t i o n the hypothesis  can be advanced t h a t closeness  to the  t a p e t a l l a y e r of the anther l o c u l e becomes more important i n c o n d i t i o n s of short n u t r i e n t supplies.There  was  no d i r e c t  evi-  dence t h a t such a phenomenon occurred. D i f f e r e n c e s i n p o l l e n v i a b i l i t y between Puck and Bonny Best appear to be produced by p h y s i o l o g i c a l p r o b a b l y i s able to c a r r y on photosynthesis  characters,Puck at a g r e a t e r r a t e  than Bonny Best.Such c h a r a c t e r s are undoubtely g e n e t i c a l l y cont r o l l e d and data i n t a b l e X I I showing marked d i f f e r e n c e s between r e c i p r o c a l P1 h y b r i d s suggest i n h e r i t a n c e i n a maternal f a s h i o n . However,more c o n t r o l of environmental c o n d i t i o n s i s necessary t o reduce the l a r g e v a r i a b i l i t y showing up i n experiments of t h i s type,and to i n c r e a s e the r e l i a b i l i t y of c o n c l u s i o n s  there-  from. Lack of c o n t r o l of the environmental c o n d i t i o n s i n which p o l l e n was  produced was probably the main source of p o l l e n va-  r i a b i l i t y i n the germination  experiments.The greenhouses i n  which p l a n t s were grown are r a t h e r u n s a t i s f a c t o r y when a very p r e c i s e c o n t r o l of the f l o w e r microenvironment i s r e q u i r e d , f i r s t of a l l , l i g h t i s cut down to a. l a r g e extent by the g l a s s ,  - 62 and s e c o n d l y , s h a d o w i n g , p a r t i c u l a r l y i n sunny d a y s , v a r i e s from p l a c e t o p l a c e d u r i n g the day,owing to the r e l a t i v e  position  of the sun w i t h r e s p e c t to other p l a n t s , w a l l s , a n d greenhouse supporting structures. Temperatures change i n d i f f e r e n t p l a c e s at very s h o r t d i s t a n c e s mainly i n r e l a t i o n to the p o s i t i o n of the h e a t i n g pipes,and to the d i s t a n c e from the g l a s s w a l l s . F u r t h e r v a r i a b i l i t y i s i n t r o d u c e d by sun heat i n p e r i o d s of clear- weather or a l t e r n a t e c l o u d i n e s s . F i n a l l y , a i r drafts, p a r t i c u l a r l y those produced by the h e a t i n g c o i l s put underneath the benches,are an a d d i t i o n a l source of v a r i a b l e heat d i s t r i b u t i o n . R e l a t i v e humidity was probably .also c o n t r i b u t i n g to a c e r t a i n extent to p o l l e n germination v a r i a b i l i t y , e s p e c i a l l y when c o o l i n g of the houses was  obtained by s p r i n k l i n g the warm  concrete a i s l e s between benches. The sampling technique was not completely  satisfactory,  s i n c e to obviate to the d i f f i c u l t y of h a v i n g p o l l e n of the same age,sampling should be done on l a r g e masses of g r a i n s c o l l e c t e d and mixed from a l a r g e number of f l o w e r s . I n p r a c t i c e there were two r e s t r i c t i o n s to t h i s : a ) a n t h e s i s i s s c a l a r i n tomatoes,thus r e d u c i n g the number of f l o w e r s i n blossom at any one time,so t h a t c o l l e c t i o n of l a r g e samples r e q u i r e s more p l a n t s than i t was p o s s i b l e to grow;b) c o l l e c t i o n of p o l l e n by hand n e c e s s a r i l y l i m i t e d the s i z e of the masses on which sampling was  done,and by d e s t r o y i n g sampled f l o w e r s reduced  furthermore the number of f l o w e r s a v a i l a b l e on s u c c e s s i v e dates.  - 63 There are two hypotheses which can he advanced from the r e s u l t s of these experiments; a) t h a t d i f f e r e n c e s i n p o l l e n v i a b i l i t y between tomato v a r i e t i e s are dependent upon g e n e t i c a l l y c o n t r o l l e d p h y s i o l o g i c a l c h a r a c t e r s , s u c h as a b i l i t y t o make carbohydrates •available to the maturing t e t r a d s i n the anthers,even under u n f a v o r a b l e env i r o r m e n t a l c ond i t i ons.j b) t h a t p o l l e n of a l l v a r i e t i e s i s h i g h l y s e n s i t i v e to the conditions  of the microenvironment,with a l o s s of g e r m i n a b i l i t y  ensuing q u i c k l y under the a c t i o n of s e v e r a l d i f f e r e n t f a c t o r s . Both hypotheses c a l l f o r f u r t h e r i n v e s t i g a t i o n s under b e t t e r control, of both the f l o r a l micro- and macro-environments •  - 64 SUKMARY AN CONCLUSIONS Greenhcmse and c y t o l o g y c a l experiments on the tomato v a r i e t i e s Puck, Bonny Best and t h e i r r e c i p r o c a l P1 h y b r i d s were performed t o a s c e r t a i n s u i t a b i l i t y o f Puck i n a b r e e d i n g programme aiming a t producing new tomato v a r i e t i e s .for the growing r e g i o n s of t h e North American, c o n t i n e n t , which are characterized  bv low s p r i n g temperatures, and/or short season.  B r u i t s e t t i n g and e a r l i n e s s i n the tomato depend upon s e v e r a l f a c t o r s , and were s t u d i e d i n an experiment conducted i n greenhouses where p l a n t s were grown a t two temperature ranges, namely 55°to 65°,and 65°to 75°P.. The l a t t e r were c o n s i d e r e d optimum temperatures f o r growth and development of tomato  plants.  a) Greenhouse Experimentsj 1) E f f e c t s of temperature on f l o w e r production; 2) E f f e c t s of temperature on v a r i e t y c o m p a t i b i l i t y relationships; 3) E f f e c t s o f seed s e t on e a r l i n e s s of f r u i t s , b) C y t o l o g i c a l Experiments; 1) E f f e c t s o f temperature on microspore development; 2) E f f e c t s o f temperature on p o l l e n v i a b i l i t y ; 3) G e r m i n a b i l i t y o f p o l l e n produced a t normal temperature. Temperatures below the optimum range f o r t h e tomato were found t o i n c r e a s e  s i g n i f i c a n t l y t h e number of f l o w e r s produ-  ced on a l l v a r i e t i e s . A t low temperatures the increase  produ-  ced on the h y b r i d s compared t o that o c c u r r i n g on Bonny Best was s i g n i f i c a n t . A t the lower range of temperature a s i g n i f i c a n t r e d u c t i o n of f r u i t s e t t i n g occurred,suggesting changes i n the c o m p a t i b i l i t y  - 65 r e l a t i o n s h i p s between v a r i e t i e s . A c l e a r - c u t t r e n d r e v e a l e d by the c o n t r o l l e d p o l l i n a t i o n experiment was a marked i n c r e a s e i n number of f r u i t s e t on P1 h y b r i d s when c r o s s - p o l l i n a t e d w i t h any one of the o t h e r v a r i e t i e s i n the experiment,than when s e l f - p o l l i n a t e d , T h e s e r e s u l t s suggest a r e d u c t i o n of s e l f c o m p a t i b i l i t y i n the h y b r i d s produced by temperatures below the optimum,and l i m i t the convenience of P1 h y b r i d s f o r commercial production. The number of days between p o l l i n a t i o n and m a t u r i t y of f r u i t s was found t o be i n v e r s e l y r e l a t e d t o the number of seeds formed i n the f r u i t s . S i n c e reduced seed content probably f o l l o w reduced c o m p a t i b i l i t y , v a r i e t i e s I n which low temperatures  pro-  duce r e d u c t i o n of s e l f - c o m p a t i b i l i t y , a r e not f i t f o r e a r l y p r o ^ d u c t i o n i n areas where c o o l s p r i n g temperatures are usual,and wherever growing seasons are s h o r t . Low t e m p e r a t u r e s , p o s s i b l y i n t e r a c t i n g w i t h low l i g h t i n t e n s i t y and s h o r t photoperiod,appear t o reduce markedly the v i a b i l i t y of p o l l e n on a l l v a r i e t i e s , p r o b a b l y through reduct i o n of the n u t r i e n t supply a v a i l a b l e t o the maturing p o l l e n tetrads.Low temperatures were found to d e l a y completion of m e i o s i s over a l o n g e r than u s u a l p e r i o d of time,and t h i s delay was b e l i e v e d t o enhance the e f f e c t s of n u t r i t i o n a l c o m p e t i t i o n among t e t r a d s maturing i n c o n d i t i o n s o f n u t r i e n t shortage,and at l e a s t p a r t i a l l y account f o r p o l l e n degeneration. Despite the h i g h v a r i a b i l i t y of the data f o r v i a b i l i t y of p o l l e n produced a t low temperatures s i m i l a r i t i e s between  - 66 means of Puck and (PxBB) ,and Bonny Best and (BBxP) F)  F/  suggested  an e x t r a n u c l e a r i n h e r i t a n c e of the c h a r a c t e r " p r o d u c t i o n of v i a b l e p o l l e n at low temperatures".However,such  r e s u l t s can  not be c o n s i d e r e d c o n c l u s i v e . The i n v e s t i g a t i o n on p o l l e n g e r m i n a b i l i t y was conducted on m a t e r i a l produced at normal temperature,and showed an unexpected v a r i a b i l i t y i n g e r m i n a t i o n percentages.Owing t o i n c o n s i s t e n c y of r e s u l t s no d e f i n i t e t r e n d emerged from those o b s e r v a t i o n s . T h i s i n d i c a t e s the need f o r more c l o s e c o n t r o l of the f l o w e r m i c r o c l i m a t e i n experiments of t h i s t y p e . In the F1 h y b r i d s the i n c r e a s e i n number of f l o w e r s formed a t low temperatures i s p a r t i a l l y counterbalanced by a r e d u c t i o n i n s e l f - c o m p a t i b i l i t y which reduces the convenience of the commercial use of f i r s t g e n e r a t i o n h y b r i d s . Puck produces a h i g h e r number of f l o w e r s , h a s no r e d u c t i o n of c o m p a t i b i l i t y , a l o n g w i t h c o n s i s t e n t seed s e t a t low temper a t u r e s , t h e r e f o r e i s t o be c o n s i d e r e d a v a l u a b l e source of germ plasm i n o u t l i n i n g a b r e e d i n g programme.  APPENDIX GOOD HOUSE Block I (PxBB)xBB (BBxP)xBB (BBxP)® BB® PxBB (PxBB)® BBx(PxBB) Px(PxBB)  P®  (PxBB)xP  Block I I BBx(PxBB)  BBx(BBxP)  (PxBB)x(BBxP)  PxBB  (BBxP)xP  (PKBB)®  Px(PxBB)  BBxP  (BBxP)x(PxBB)  Px(BBxP)  (PxBB)xP (BBxP)x(PxBB) (PxBB)xBB (BBxP)xP (PxBB) x( BBxP) (BBxP)® BBxP)xBB  P® BBxP BBx(BBxP) Px(BBxP_)_  Block I I I (PxBB)® (BBxP)® Px(BBxP) BBxP BB® (BBxP)xP (BBxP)xBB  - 68 -  PxBB (PxBB)x(BBxP) Px(PxBB) BBx(PxBB) P® (PxBB)xP (BBxP)x(PxBB) (PxBB)xBB  APPENDIX WARM HOUSE Block I (BBxPyiBB™ (BBxP)® (PxBB)xBB PxBB Px(BBxP) BBx(PxBB)  B l o c k II BB®  (PxBB)x(BBxP)  Px(PxBB)  (PxBB)®  (BBxP)xP  BBx(BBxP)  PxBB  (PxBB)xP BBxP (PxBB)®  BB® (BBxP)x(PxBB) BBx(BBxP) P®  -Px(BBxP)  B B  (BBxP)  P x P  (BBxP)®  *?  ® (B£xP)  xBB  JBlock III BBxP BBx(BBxP) Px(PxBB) (BBxP)xP BB® P® BBx(PxBB) (PxBB)xBB (PxBB)® fx(BBxP) PxBB (PxBB)x(BBxP) (BBxP)x(PxBB) (BBxP)xBB (PxBB)xP (BBxP)®  - 67  sb-  BIBLIOGRAPHY 1.  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