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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 the Department of H o r t i c u l t u r e We accept t h i s t h e s i s as conforming to the standard required from candidates f o r the degree of 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 desired f o r com-mercial production i n a g r i c u l t u r a l areas having r e l a t i v e l y low spring temperatures, and/or short growing seasons. These v a r i e t i e s would need the character of being able to set f r u i t under the unfavorable conditions 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 of s e t t i n g fru.it at low temperatures, but i s otherwise unsuitable f o r p r o f i t a b l e tomato production. To i d e n t i f y the mechanism of t h i s desirable character i n Puck, and mode of inheritance of the character, experiments were c a r r i e d out to study flower production, p o l l e n 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 , ' and the pro-duction, development and germination of p o l l e n . Experiments were c a r r i e d out at two temperature l e v e l s i n greenhouses to observe e f f e c t s on flower and f r u i t develop-ment. These plant responses were studied In a r e l a t i v e l y cool greenhouse kept at 55°- 65* P. and i n another house kept at 65 -75°P. range which i s considered optimum f o r tomato production. The plants 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 hybrids. Blower production was s i g n i f i c a n t l y Increased by lower temperatures, and the increases on Puck and the hybrids 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 reduction^of s e l f - c o m p a t i b i l i t y In the hybrids as w e l l as i n Bonny Best, the l a t t e r having a high i i percentage of parthenocarpic f r u i t s . The number of days between p o l l i n a t i o n and maturity of f r u i t s was found to be i n -ver 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 with low l i g h t i n t e n s i t i e s and short photoperiods, 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 with the acetocarmine s t a i n i n g procedure and with germination 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 germination, which was p o s s i b l y due to the e f f e c t s of temperature on microsporogenesis. Percentages of normal meioses were only s l i g h t l y a f f e c t e d , but there was evidence that a minimum temperature i s required f o r the completion of meiosis, and that 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 to be d i f f e r e n t i n d i f f e r e n t v a r i e t i e s . Puck had a higher number of flowers produced at low tempe-ratures ,showed no reduction of s e l f - c o m p a t i b i l i t y , and had a consistent seed set; therefore, t h i s v a r i e t y i s to be conside-red a possible source of germ plasm i n the breeding of tomatoes t o l e r a n t of cool temperatures. In presenting 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 U n i v e r s i t y of B r i t i s h Columbia, I agree that the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r reference and study. I f u r t h e r agree that permission f o r extensive copying of t h i s t h e s i s fo r s c h o l a r l y purposes may be granted by the Head of my Department or by h i s representatives. I t i s understood that 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 f i n a n c i a l gain 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 to express h i s thanks to Dr.C.A. Hornby,Associate Professor of H o r t i c u l t u r e and Chairman of the t h e s i s Committee, f o r supervision of the experimental work and f o r valuable assistance i n the preparation of the t h e s i s . Acknowledgement i s given to the other members of the th e s i s Committee; Dr.Y.C, Brink, Professor of Agronomy; Br.G.H. H a r r i s , Professor of H o r t i c u l t u r e ; Dr. A.G. Renney, Associate Professor of Agronomy;and Mr. E.L. Watson, A s s i s t a n t Professor of A g r i c u l t u r a l Mechanics. Thanks are expressed to Dr. G.E. Rouse, I n s t r u c t o r , Department of Biology and Botany, and member of the t h e s i s Committee, f o r h i s help i n the h i s t o l o g i c a l work; and to Dr. J . Sawyer, D i v i s i o n of plant Science, f o r h i s valuable cooper-a t i o n . The w r i t e r i s indebted f o r f i n a n c i a l assistance during the course of the work to 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 . M a t e r i a l s . 14 B. Methods 1 6 1 . Greenhouse Experiments, 16 2. C y t o l o g i c a l Experiments 19 a) Microsporogenesis................. 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 germination...... 23 RESULTS 1. Greenhouse Experiments, a) E f f e c t s of temperature on flower production. 27 b) E f f e c t s of temperature on compa-t i b i l i t y r e l a t i o n s h i p s 39 c) E f f e c t s of seed set on ea r l i n e s s of f r u i t s 44 2. C y t o l o g i c a l Experiments. a) Microsporogenesis.. ,.»..... 47 b) P o l l e n v i a b i l i t y 50 c) Polle n germination. 52 DISCUSSION 57 SUMMARY AND CONCLUSIONS 64 LITERATURE CITED. 67 i v INTRODUCTION The production of tomato v a r i e t i e s which can set f r u i t under conditions of r e l a t i v e l y low temperature i s of 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 conditions of temperature p r e v a i l i n g i n the e a r l y part of the growing season,frequently 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 basic 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 period of about three and one h a l f months;secondly,a minimum temperature r e -quirement of approximately 55" F. In the t r a d i t i o n a l areas of culture f o r t h i s crop i n Canada there 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 period f o r the production of tomatoes,but plants of the present commercial var-i e t i e s very often f a i l to set f r u i t on the f i r s t and second inflorescences,when exposed to nocturnal temperatures between 55° and 65°F,which very frequently occur i n the f i e l d at trans-p l a n t i n g time,and f o r a few weeks subsequently.Therefore,growers would benefit i f f r u i t s e t t i n g were consistent during 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 of growers to supply the e a r l y , more l u c r a t i v e market,and to increase t o t a l yields.Furthermore, the increased range of temperature tolerance would allow the extension of the cultu r e of the tomato to areas where,at the present time,the short season co 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 already known that an En g l i s h variety,Puck,can 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 desirable germ plasm i n a breed-i 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 cool temperatures f o r f r u i t setting.Such a programme requires a c l e a r i d e n t i f i c a t i o n of the character,or characters present i n Puck,and knowledge of the mode of i n h e r i t a n c e , a l l of which would make possible the transferring of the desi r a b l e character or characters,to 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 processes.lt has been possible to i n v e s t i g a t e only a few of the several p h y s i o l o g i c a l steps involved.Present studies were confined to blossom and f r u i t development as affected 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 physiology 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 large environmental influence upon the phenotypic expression 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 genetic c o n s t i t u t i o n and environment accounts f o r plants appearing normal under one set of conditions,and extremely d i f f e r e n t under changed cond i t i o n s . This phenomenon i s p a r t i c u l a r l y true of the d e l i c a t e processes involved i n f r u i t s e t t i n g , n a m e l y : f l o r a l 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 fa c t o r s involved i n phenotypic expression has frequently 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 i n t e r p r e t a t i o n s , F l o r a l induction and i n i t i a t i o n . The work of Lewis (30) was designed to study the genetic-environmental i n t e r a c t i o n e f f e c t s upon the character "number of flowers per cluster".Temperature and l i g h t intensity,and/or day length modified the expression of the genotype.Temperatures around 14°0.during the growing period from the expansion of cotyledons to the appearance of the f i r s t inflorescence r e s u l t e d i n production of a higher number of flowers per cluster,than f o r plants kept at 25-30" C.Lewis (29) found t h i s character to be c o n t r o l l e d by a major gene,and by a system of polygenes. Went's (48) conclusions do not agree with those of L e w i s , r e l a t -i n g f l o r a l induction and i n i t i a t i o n ^ o n l y to genetic 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 subjected to d i f f e r e n t thennoperiods,and concluded that lower temperatures at night generally increase the number of f r u i t s per cluster.The 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 reacted i n completely opposite fashion to the other nine. Wellensiek (47) c i t e s work by Verkerk that 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 rate,dry weight,number and weight of f r u i t s , a n d i n general p h y s i o l o g i c a l processes which are dependent upon carbohydrate a v a i l a b i l i t y . F l o r a l development. Normally developed tomato flowers are hypogynous,and reg-u l a r . The number of f l o r a l parts i n each cycle 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 plants are u s u a l -l y pentamerous,with a basic f l o r a l plans 5,5,5,2.Cooper (8) and Smith (41) have described hexamerous development as the most commonly occurring 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 described by Hayward (15).Fasciation i n the perianth and i n the f e r t i l e parts of the flower have been des-cribed 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 tempe-ratures and extremes i n the > carbohydrate /nitrogen r a t i o 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 pet-a l s i n f a s c i a t e d flowers may be present i n exaggerated or redu-ced number,and petals are sometimes lacking,or modified i n shape. Stamens seem to be very s e n s i t i v e to environmental i n f l u e n -ces, and any cause a f f e c t i n g normal production o f . p o l l e n i s l i k e l y to a f f e c t normal development of anthers. Howiett (18') stated that carbohydrate d e f i c i e n c i e s r e s u l t sometimes i n suppression of the male organs, thus becoming a l i m i t i n g f a c t o r i n the sexual expression of tomato p l a n t s . He reported f l o r a l a b s c i s s i o n at bud stage under very severe carbohydrate short-age. Increasing a v a i l a b i l i t y of carbohydrates r e s u l t e d progres-s i v e l y i n blossoms reaching anthesis, i n c r e a s i n g percentages of v i a b l e microspores, and f i n a l l y i n the production of normal p o l l e n grains. Microspore degeneration was found at any time f o l l o w i n g the second meiotic d i v i s i o n , and frequently normally appearing grains were found to be non-functional. As possible causes of carbohydrate shortage, Judkins (22) suggested periods of low l i g h t i n t e n s i t y which reduced production of v i a b l e p o l -l e n . Johnson et al.(21) found cases where sugar t r a n s l o c a t i o n from the leaves was impaired by nocturnal temperatures. In general, carbohydrate shortage during the process of p o l l e n maturation i n tomato plants appeared to 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 responsible 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 (36). Gene mutation i n the broad sense i s responsible f o r s t e r i l i t y of some d i p l o i d plants to an extent which only r e c e n t l y has been appreciated. There are many reports on gene muiation a f f e c t i n g charac-- 6 -te r s of the flower and of the inflorescence (14,24,27,37). Five asynaptic mutants described by Soost (44) are of cytoge-n 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 meiotic stages.A c l e i s t o -gamous mutant,in which no anthesis occurs,has been reported by Rick and Robinson (38),under c e r t a i n f i e l d conditions;and Bishop (1) described the reduction of stamens to vestiges.Paddock and Alexander (34) described a mutant i n which inflorescences kept growing and branching without producing any flowers. F a s c i a t i o n of the p i s t i l occurs frequently on plants grown at low temperatures (51).Supranumerary s t y l e s may be present i n the same flower,usually fused along t h e i r length,and extra-locu-l e s may produce abnormally shaped ovaries,and subsequent f r u i t s , i f they are able to develop. Among the anomalies of the pistil,however,the most frequent-l y discussed i s s t y l a r exserti)n.Cultivated v a r i e t i e s u s u a l l y d i f f e r from w i l d types by having t h e i r stigmas located w i t h i n the staminal cone.It has been suggested (37) that the change from a moderately c r o s s - p o l l i n a t e d species to a con d i t i o n of exclusive s e l f - p o l l i n a t i o n , o c c u r r e d when the tomato was i n t r o -duced i n Europe from South America.lt was probably due to the change of p o s i t i o n of the stigma w i t h respect to the anthers that c l o s e r imbreeding made i t possible to f i x many recessive characters 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 types. Burk (5) reported that length of the s t y l e i n Bonny Best - 7 -v a r i e d according to the length of the photoperiod,and to the i n t e n s i t y of l i g h t ; 8 hours of photoperiod g i v i n g longer 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 e f f e c t s s i m i l a r to those of short 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 elongation. S i m i l a r observations were made by Bouquet (3) and Smith (40).The l a t t e r reported the e f f e c t s of the i n t e r a c t i o n between high temperatures and low humidity produced by hot,dry winds, r e s u l t i n g i n abnormal s t y l a r elongation even before anthesis, i n such a way reducing f r u i t set through impaired p o l l i n a t i o n , retarded tube growth,and f l o r a l a b s c i s s i o n , Howlett (18) found nitrogen d e f i c i e n c y much more e f f e c t i v e i n b ringing about s t e r i l i t y of the female sex c e l l s than carbo-hydrate shortage,and subsequently found nitrogen/carbohydrate imbalance to be the cause of s t y l a r elongation(19).Conditions impairing carbohydrate synthesis or r e s u l t i n g i n increased r e s p i r a t i o n rates,and any other condition producing 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) reported on the act i o n of an enzyme i n a c t i v a t i n g indole a c e t i c a c i d i n e t i o l a t e d pea seedlings. They..found,also,a water-soluble,thermostable 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 indole a c e t i c a c i d i n a l l plants investigated.The formation of t h i s f a c t o r i s promo-ted by l i g & t ;longer exposures to l i g h t lower the amount of act i v e enzyme,so enhancing the act i o n of the indole 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 indole 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 elongation to the high temperatures and l i g h t i n t e n s i t i e s .Leopold and Scott (25) found no e f f e c t s of auxin shortage on f r u i t set,but thought the s e t t i n g and de-velopment of f r u i t was c o n t r o l l e d by the carbohydrate supply. Rick and Robinson (38) described a mutant showing abnormal s t y l a r elongation,and t h i s character was very 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 asynaptic mutants. F i n a l l y , o f great g e n e t i c a l importance,on the same subject of s t y l a r elongation i s the report by Currence (10) exp l a i n i n g the inheritance of t h i s character on the basis of a duplicate 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 to 48 hours a f t e r the opening of the corolla,under optimal environ-mental conditions ( 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 insects,the bumble-bee being the most common v i s i t a n t . Unfavorable conditions may impair 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 causing reduction i n p o l l e n germination, and slowing the rate 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 at optimum temperatures.According to Smith and Cochran (42),temperatures of 70"to 85"F.permit the highest percentage of p o l l e n germin-ation;and 70°P.allow the maximum rate of growth of the p o l l e n tube.Under favorable conditions 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 increase i n the time involved i n po l l e n tube growth during f a l l and winter,when l i g h t i s of low intensity.He did not attempt to explain those observations e i t h e r on the basis of s t y l a r anatomy or p o l l e n v i a b i l i t y . According to Went (48),thermoperiodicity i n tomatoes i s due to the predominance of two d i f f e r e n t processes,one a day-l 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 pro-cess .This r e l a t i o n holds f o r plant growth,as w e l l as f o r f r u i t set.Furthermore,it was noticed that a r t i f i c i a l l i g h t when applied during the cool night period,completely i n h i b i t e d f r u i t formation. The i n v e s t i g a t i o n s of Leopold and Scott (25) l e d to the conclusion that besides the w e l l known temperature-sensitive functions,such as growth of the style,reduced 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 tempe-rature 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 to 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 small,or of poor quality.However,Hawthorn ( 1 6 ) reported that a cross between Large Cherry and Bonny Best varieties,produced seedless,good q u a l i t y and abundant f r u i t s i n midsummer.The same plants had ea r l y and l a t e maturing f r u i t s - 10 -with, seeds. According to G-ustafson (13),auxin content of the ovaries may he high enough to set 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 leaves. Such conclusions 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 synthetic growth sub-stances to n u t r i e n t s o l u t i o n s of unpollinated,excised tomato ovaries. There i s evidence that parthenocarpic f r u i t s , b e s i d e s being smaller i n s i z e and weighing l e s s than seeded ones,are l a t e r r i p e n i n g (46),a character of primary importance i n the develop-ment of new v a r i e t i e s f o r e a r l y production under low spring temperatures. E f f e c t s of temperature on p o l l e n germination and tube growth. There i s evidence that 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 rate of growth(42). The e f f e c t s of low temperatures on other crops such as plums and apples have been reported 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 conditions (39). In the tomato the optimum temperature f o r p o l l e n germina-t i o n was found to be 85" E.,whereas the maximum growth rate oc-curs at 70° E.,gradually d e c l i n i n g at both lower and higher tempe-ratures (42). - 1 1 -Lewis (28) obtained marked differences between the growth rates of compatible and incompatible p o l l e n tubes w i t h i n the same style,by c u l t u r i n g p o l l i n a t e d flowers at d i f f e r e n t tempe-ratures.The rate of growth of compatible tubes i d generally increased f o l l o w i n g temperature increases,and 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 opposite behaviour;thus,at optimum temperatures,dif-ferences i n length beween the two types of p o l l e n tubes are at t h e i r maximum. Richardson and Currence (35),following 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 small but s i g n i f i c a n t differences i n e a r l i -ness of P2 plants grown from seeds taken from stem halves as compared to plants grown from seed i n blossom halves of the same f r u i t s . V a r i e t a l differences i n a b i l i t y of p o l l e n to set f r u i t s over more or l e s s wider 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 able to set f r u i t on Pearson under temperatures at which Pearson p o l l e n was unable to set 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 suggesting a genetic difference between the two v a r i e t i e s i n production of v i a b l e pollen,germination of pollen,and f e r t i l i z a t i o n at low temperatures. Meiosis. The behaviour of chromosomes at meiosis has been studied mainly on p o l l e n mother c e l l s , a n d was s t a r t e d by Lesley ( 2 6 ) as e a r l y as 1 9 2 6 . P r i o r to that time,Winkler ( 4 9 ) had discovered that the tomato has -a somatic number of 24»and a gametic number of 1 2 chromosomes.Meiosis i n the tomato follows the regular pattern 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 ion to give t e t r a d groups of 1 2 chromosomes each.Cytokinesis follows,and a f t e r a period of maturation,microspores are r e l e a -sed. The starch rich,, .opaque l a y e r i n the w a l l s of the mature microspores does not allow f o l l o w i n g the f i r s t postmeiotic mito-s i s , about which very l i t t l e i s known;the generative 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 divides 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 normally occurs at a l l stages between zygotene and metaphase of the f i r s t meiotic d i v i s i o n . A few ex-ceptions to t h i s r u l e occur owing to abnormal conditions such as heteroploidy,gene-controlled chromosome disturbances,or sub-l e t h a l temperatures (37).Soost (44) found temperatures around 95°1? .were more e f f e c t i v e than temperatures around 50° P . f o r pro-ducing abnormalities i n meiosis. According to Hayward ( 1 5 ) , i t i s t y p i c a l of the second re-duction d i v i s i o n i n the tomato,that metaphase,anaphase,and t e l o -phase may occur simultaneously i n a s i n g l e l o c u l e . Cytoplasmic inheritance. Extranuclear inheritance i n the tomato i s not f u l l y under-- 13 -stood yet,despite i t s rather 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 allow crosses of many combinations to be made i n one d i r e c t i o n only. Chlorophyll d e f i c i e n c i e s have been found to be i n h e r i t e d i n maternal fashion,being transmitted to progeny only i f the 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 con d i t i o n of the male parent (31). Transmission of such characters as plant h e i g h t , y i e l d s , and f r u i t shape,in some instances have been explained on the basis of cytoplasmic inheritance.In these cases P1 hybrids of 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 other mating of the same i n t e r v a r i e t a l cross (37). - 14 -MATERIALS AND METHODS A. M a t e r i a l s . The plant materials 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 hybrids. Puck. Puck was introduced from England,where I t had been d e s c r i -bed by Crane (9).Puck was selected from segregating 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 released from Russia at the end of World War I I . Puck has a determinate growth habit and i s characterized by a woody stem,strong enough to bear the weight of the f r u i t s i n the early period of growth.The main stem terminates i n a l e a f and c a r r i e s a double inflorescence i n the l a s t internode. A x i l l a r y side-shoots develop from buds,and have determinate . growth as well.They may carry s i n g l e clusters,but i n the l a s t internode double ones u s u a l l y occur.The indeterminate habit of growth i s conditioned by a s i n g l e recessive gene sp ( f o r s e l f -pruning) , located i n the s i x t h chromosome,and belonging to the f o u r t h linkage 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 surface.Bruit s i z e i s medium, colour uniform, and shape sometimes I r r e g u l a r .The fru.it w a l l i s d i f f e r e n t i a t e d from the placenta and at maturity the l a t t e r l a c ks the f l e s h y character of commercial v a r i e t i e s . The Puck variety,described as an e a r l y producer,has been shown to require a greater 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 conditions (11). 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 commer-c i a l v a r i e t i e s already grown i n the province of B r i t i s h Columbia, despite i t s aknowledged character of being able to set f r u i t s at low temperatures (12).On the other hand,it i s t h i s character that makes i t a p o t e n t i a l source of valuable germ plasm f o r improvement of v a r i e t i e s otherwise acceptable f o r commercial production. • Bonny Best. 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 since the e a r l y years of t h i s century,following i n t r o d u c t i o n by the f i r m of Johnson and Stkes of P h i l a d e l p h i a . Bonny Best has indeterminate growth;round ,fleshy,uniformly coloured f r u i t s . I t i s r e l a t i v e l y early,but 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 represent the commercial v a r i e t i e s because i n the past t h i r t y years a considerable amount of research 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 hybrids. F i r s t generation hybrids 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 possible maternal inheritance.Plants 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 previous years at the U n i v e r s i t y of B r i t i s h Co-lumbia.The hybrids resemble Bonny Best plants i n t h e i r general appearance,have the indeterminate habit,and grow f a s t e r and t a l -l e r than Bonny Best plants.Leaf width,thickness,surface and colour are intermediate between the same characters i n the parent v a r i e t i e s . 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 of B r i t i s h Columbia i n the winter of 1958 - 1 9 5 9 to contrast response of the plant materials at the r e l a t i v e l y cool temperatures of 55*to 6 5 " P . w i t h the nearly optimum range of 65" to 7 5 * F. f o r the tomato.. Seeds of the four stocks,Puck,Bonny Best and t h e i r r e c i p r o -cal" hybrids were sown on November 24,1958,and seedlings were pricked out and set 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 possible between 5 5 " and 65°P.for the cool house,and 65'and 75°F.for the warm house. Temperature records were obtained f o r the duration of the experi-ments by means of thermographs.All seedlings 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. Controlled 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 duration of two months.First p o l l i n a t i o n s were made on December 1,and December 2 9 , i n the warm and i n the cool 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 tem-perature i n the cool house went above 65° P. on eleven p a r t i c u -l a r l y bright days,but only s i x times f o r periods longer 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 only f i v e times below 60°F.for very short periods. The benches used f o r t h i s experiment were p a r a l l e l to the north-south w a l l s i n both houses,one r e p l i c a t e being along the northern 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 given i n the amount of one pound superphosphate on each bench,equivalent to 650 lb/acre.Analysis 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 high contents of nitrogen,phosphorus,and potassium. The plants were set i n the benches on November 6,1958. i n d i v i d u a l p l o t s consisted of one plant,and a randomized block design w i t h three r e p l i c a t i o n s was used i n each house.The plan of the experiment i s shoam i n appendix I,Plants were spaced 20 inches apart between rows,and 15 inches apart w i t h i n rows. To provide supplementary l i g h t under the seasonal conditions of decreasing l i g h t i n t e n s i t y and photoperiod,!our 500 watt fluorescent 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 provided i n the morning and also i n the evening to insure an eighteen hour photoperiod. A l l plants except those of the determinate Puck v a r i e t y - 1 8 -were pruned to a s i n g l e stem,and staked. The p o l l i n a t i o n studies consisted of sixte e n treatments to have a l l four l i n e s s e l f - p o l l i n a t e d and also c r o s s - p o l l i n a t e d i n a l l possible 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 follows,showing 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 future reference to the treatments. Treatments. Symbols. 1. Puck x Puck m 2. Puck x Bonny Best PxBB 3. Puck x (Puck x Bonny Best) F I Px(PxBB) 4. Puck x (Bonny Best x Puck) F l Px(BBxP) 5. Bonny Best x Bonny Best BBS 6. Bonny Best x Puck BBxP 7. Bonny Best x (Puck x Bonny Best) F ( BBx(PxBB) 8 . Bonny Best x (Bonny Best x Puck) F, BBx(BBxP) 9 . (PuckxBonny Best) f l x(PuckxBonny Best) F, (PxBB)® 10. (Puck x Bonny B e s t ) R x Puck (PxBB)xP 11. (Puck x Bonny Best) P lx Bonny Best (PxBB)xBB 12. (PuckxBonny Best) F, x(Bonny BestxPuck) f l (PxBB)x(BBxP) 13. (Bonny Be stxPuck) F l x( Bonny BestxPuck) F ( (BBxP)a 14. (Bonny Best x Puck) F l x Puck (BBxP)xP 15. (Bonny Best x Puck) f l x Bonny Best (BBxP)xBB 16. (Bonny BestxPuck) F lx(PuckxBonny Best) F I (BBxP)x(PxBB) Second,third,and f o u r t h inflorescences 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 discarded because they were - 19 -w e l l developed at the time of t r a n s p l a n t i n g to benches,and flowers opened i n both houses a few days l a t e r , t h u s development of those flowers would not have been influenced by the contras-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 flowers were emasculated one day before anthesis by taki n g away petals and anthers w i t h a p a i r of tweezers.Pollen was c o l l e c t e d on microscope slides,and applied by dipping the stigmas on the mound of 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 of p o l l e n were repeated twice on each flower at two-days i n t e r v a l s i n order.to reduce the e f f e c t s of 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 labeled to make i t possible to c o l l e c t the 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 ) P o l l i n a t i o n treatment. i i ) Bate of p o l l i n a t i o n , i i i ) Number of days between p o l l i n a t i o n and f r u i t maturity. Other data recorded were: i ) Number of blossoms on f i r s t four trusses. i i ) Number of seed per f r u i t , i i i ) Percentages of parthenocarpic f r u i t s . The data c o l l e c t e d were subjected to analysis of variance 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 observations were made to asc 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 conditions of temperature on m e i o s i s , v i a b i l i t y , and germination of p o l l e n . a) Microsporogenesis. Microsporogenesis was studied by means of a smear technique. Buds were taken f o r examination at a s i z e of approximately 4 mm. i n length,although the optimum s i z e f o r observing the meiotic stages was found to vary among d i f f e r e n t v a r i e t i e s , a n d according to the p o s i t i o n of the bud on the inflorescence,and of the l a t t e r on the plant 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 used; a) B e l l i n g ' s iron-acetocarmine,and b) Feulgen's reagent,both prepared using 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 better results,and was found to be time-saving as compared to 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 introducing 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 (44). 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 ace 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 three hours,then washed i n tap water f o r twenty minu-t e s , and mordanted f o r one hour.After washing f o r twenty minutes anthers were dissected with a needle i n a drop of 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 gently heated u n t i l microscopic examination revealed the optimum s t a i n i n g . S l i -des were f i n a l l y sealed with f i n g e r n a i l p o l i s h , C.R.A.F.fixative (20) was used with the expectation of im-proving r e s u l t s w i t h the Feulgen 1s,but no benefit was obtained. The p a r a f f i n method, as out l i n e d by Johansen (20)was used f o r preparing permanent slide s , b u t once again r e s u l t s were un-s a t i s f a c t o r y with Peulgen's,and no bet t e r with acetocarmine. Both s t a i n s f a i l e d to d i f f e r e n t i a t e chromosomes w i t h i n the nu-c 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 observations were taken from plant of Puck,Bonny Best and the r e c i p r o c a l hybrids grown i n pots and kept i n the sarnie greenhouses where plants f o r the p o l l i n a t i o n experiment were being grown,Eight plants 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 plants of the 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 ma t e r i a l undergo-ing meiotic d i v i s i o n presumably under s i m i l a r conditions of 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 of the buds.After preliminary observations,it was noted that the oc-currence of d i v i d i n g c e l l s was higher i n samples taken i n the morning,therefore,buds were always c o l l e c t e d at 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 to asc e r t a i n the frequency of deviations from regular meiotic patterns as affected by temperature. Observations were started i n the second h a l f of November when buds began to reach appropriate size,On each s l i d e several hundred p o l l e n mother c e l l s were present,and some of them, selected, at random1 were c a r e f u l l y examined.The nature of occur-- 2 2 -r i n g abnormalities was recorded,but no attempt was made to ex-press 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 examined. b) 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 tested w i t h the standard acetocarmi-ne s t a i n i n g procedure i n which darkly stained grains are con-sidered viable.This procedure consist s of dusting p o l l e n on a slide,soaking i t i n a drop of acetocarmine,placing a c o v e r s l i p and gently- heating the s l i d e s before examining under the micro-scope .Empty ,non-viable grains 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 of,or low content of starch i n the walls.The chromatic r e a c t i o n , i n f a c t , i s de-pendent on the presence or absence of starch i n the grains,and i t i s very 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 starch w i t h potassium iodide-iodine s o l u t i o n . The p o l l e n produced i n the warm house and tested f o l l o w -ing the ou t l i n e d technique was the same mate 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 st a r t e d on "December 1 1 , 1 9 5 8 and c a r r i e d on u n t i l January 2 6 , 1 9 5 9 , a t one-day intervals.One hundred grains were counted on each date f o r each tomato line,and the numbers of v i a b l e grains expressed as a percentage of the t o t a l s coun-ted. - 25 -In the cool house the sampling technique was n e c e s s a r i l y changed,because p o l l e n production was lower and l a t e r on a l l lines,and e s p e c i a l l y on Bonny Best.In f a c t , i t was necessary to wait u n t i l March to get plants of the four stocks contempo-raneously at anthesis.On March 12,1959,ten flowers of 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 of the v a r i e t a l germination 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 at both temperature l e v e l s . Considering Howlett 1s (18) report that p o l l e n grains which appear normal i n shape and external appearance are often n o n - v i a b l e , i t was decided to in v e s t i g a t e the v i a b i l i t y of the p o l l e n by conducting germination experiments i n v i t r o . c) P o l l e n germination experiments. Experiments on p o l l e n germination were c a r r i e d out i n v i t r o because the procedure permitted the use of c o n t r o l l e d conditions;and the study of some fa c t o r s a f f e c t i n g germination could be observed better than on plants i n the v a r i a b l e environ-ment of the greenhouses.The objective of these experiments was a) to compare the e f f e c t s of d i f f e r e n t temperatures on germi-nation of p o l l e n of 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 appropriate time i n t e r v a l s , t o observe the speed of p o l l e n germination of 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 fo l l o w s ; - 24 -i ) 10°0. as the minimum required temperature f o r tomato growing; i i ) 15° C. as the temperature frequently occurring i n the f i e l d i n e a r l y spring; i i i ) 20°C. as the optimum temperature f o r p o l l e n germination and growth,as found by Smith and Cochran (42).Such tempe-ratures correspond to 50°,59and 68°F.,and were obtained wit 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 evident,in repeated observations,that 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 i n h i b i t i n g 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 germi^hation speed were dicontinued. 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 containing 30 ppm. of boron,as ou t l i n e d by Chiscon f o r germi-nation 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 burst tubes i n i n i t i a l stages of growth was ex-tremely high and prompted a preliminary 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 concentrations of the media.A ser i e s of media containing concentrations 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 several blossoms,thoroughly mixed and dusted on microscope s l i d e s . Then drops of the d i f f e r e n t media at room- temperature were were placed 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 to the me-dia.The s l i d e s were q u i c k l y inverted over w e l l - s l i d e s and sea-l e d with vaseline.These tests f o r optimum sucrose concentration i n the media were c a r r i e d out i n the warm greenhouse,and r e p l i -cated on two dates.Counts were taken a f t e r 24 hours,and the me-dium containing 10$ sucrose was found to give the highest per-cent of p o l l e n germination,therefore,this concentration was used i n subsequent experiments. With the "lOft sucrose concentration f u r t h e r i n v e s t i g a t i o n s showed that i n absence of boron no germination took place. The procedure adopted f o r f u r t h e r experiments was as f o l -lows.Pollen from f r e s h l y dehisced anthers was collected,dusted on s l i d e s , t h e n s t i r r e d i n a drop of sucrose s o l u t i o n brought to room temperature.The s l i d e s were inverted on w e l l - s l i d e s , sealed w i t h vaseline,and kept i n c o n t r o l l e d temperature cham-bers at the three chosen l e v e l s f o r 24 hours.Counts were taken on a microscope f i t t e d with a graded ocular,and grains i n which the length of the p o l l e n tube was at l e a s t equal to the diameter of the gr a i n were considered to have germinated (39). The counts of germinated p o l l e n were made on samples of 200 grains,and t h i s experiment was repeated on f i v e d i f f e r e n t dates. The germination experiments y i e l d e d data showing a much higher v a r i a b i l i t y than was expected to occur i n p o l l e n produ-ced at the temperature l e v e l of the warm house.It appeared possible that p h y s i o l o g i c a l age of p o l l e n could have c o n t r i -buted to 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 rates of dete-- 26 -r i o r a t i o n occurring a f t e r dehiscence of the anthers i n d i f f e -rent varieties.The f o l l o w i n g experiment was set up to 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 having flowers at d i f -f e r ent stages of anthesis were chosen,and stages of anthesis were numbered.Pull bloom was considered number 1,and i n c r e a -sing numbers were assigned to e a r l i e r stages,the highest num-ber being that of the flower i n which petals were r e f l e x e d , and anthers already turning yellow,though not yet dehisced, the number of flowers i n intermediate stages v a r i e d between three and f i v e i n d i f f e r e n t clusters.Average percentages of germination were obtained from two counts of 200 p o l l e n grains per flower,and the experiment was repeated on three dates. - 27 -RESULTS A. fireer^quse Experiment. a) E f f e c t s of temperature on flower production. The number of flower buds formed on Puck and Bonny Best was found to be influenced by temperature as shown i n the da-t a of tables 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 temperatu-res being the main concern of the experiment,it was desirable to combine data from the cool and the warm houses f o r s t a t i -s t i c a l evaluation. However,it was impossible to subject the data of table I and I I to separate analyses of variance,because i n both sets the condition of homogeneity of variance 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 data were transformed by means of the logarithmic transformation as shown i n tables 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 table I I I gives a helow the value r e q u i -red 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 trans-formation having been successful,a combined analysis of the data of a l l four v a r i e t i e s has been possible,as given i n table III,and i t i s seen that there were s i g n i f i c a n t differences between varieties.The number of flowers 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 greater 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 differences 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 t r u s s . By inspection of the data i n tables I and I I I , i t i s e v i -- 28 -dent that .the r e c i p r o c a l s were very s i m i l a r to Bonny Best, suggesting a mendelian type of inheritance of the l e t t e r ' s genie c o n t r i b u t i o n to the genetic c o n s t i t u t i o n of the hybrids. S i m i l a r l y i t can be deduced that differences between the hy-brids and Bonny Best are probably due to the condition of heterozygosity of the hybrids. The s i g n i f i c a n t l y greater variance i n Puck data, as r e -vealed by B a r t l e t t ' s test,, leads to the conclusion that 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 others, and to analyse the l a t t e r separately. 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 table I I f o r which the logarithmic transformation shown i n table IV f a i l e d to reduce the heterogeneity of the variance. - 2 9 -Table I„Number of flower buds formed on first four trusses of Puck,Bonny Best,and their reciprocal hybrids grown at temperatures below 65°P. Variety Block Truss I II III IV Totals p£ck 1 7^ 4 1 3 ^ 4 2 m ™ II 64 44 28 44 180 I I I 51 32 3°l 22 l | i T 8 2 117 103 125 527 Bonny Best I II III 22 22 25 27 22 "6*8 74 "25" 31 21. "80 "23 9^ 22 102 22 91_ 289 "rpxBB) I II III I B B X P J I II IH_ 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 Bartlett 1s test Variety 28 25 25 24 25 _23_ 72 24 28 2 S »S • 47994T48 3,089.73 44.04 296.23 142.46 1,127.18 29.96 264.88 27 33 26 103 111 30. 312 22 19 22 30 27 23 29 30 16 57 78 9 6 404 330 337 374 Blocks 93 478 109 502 115 465 _ 317 1445 M.S. 1,629.91 22.02 98.74 23.74 125.24 4.99 14.71 Puck B. B. (PxBB) (BBxP) 24,649 7,045 8,194 8,607 23,144.08 6,960.08 8,112.00 8,374.08 = 1,504.92 84.92 82.00 232.92 136.81 7.72 7.45 21.17 y , = [(44x1.16776)-11(2.13612+0.88762+0.87239+1.32580)] 2.3026= =(51.381-57.441)2.3026 = 13.95 Required XW^] = 7' 8 1 - 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 Block Truss I II i l l IY Totals Puck I 51 35 22 19 127 II 45 23 20 24 112 III 52. 19 24 31 126 t 4 8 - 77 5^ 74 —53^-Bonny Best I 20 21 25 25 91 II 20 24 23 24 91 III 20 21 22 25 88 60 '66 70 74 270 (PxBB) I II III 22 20 2A 19 24 18 24 23 23 24 24 29 89 90 66 61 70 76 273 Blocks (BBxP) I 23 19 24 23 89 396 II 26 21 27 28 102 395 III 2± 21 25 27 i L „ _ i Q 5 _ 73 61 76 78 288 347 265 282 302 1196 Analysis of variance. Source D.F. S • S • M.S. Total 47 2, 421."67 -Varieties 3 499.50 166.50 Blocks 2 3.79 1.89 Trusses 3 313.17 104.39 Var.xBlock 6 57.88 9.64 Var.xTruss 9 1, 273.66 141.51 Block xTruss 6 97.21 16.20 Error 18 176.46 9.80 Bartlett's test for homogeneity of variance. Variety S. S. Variance Puck B.B. (PxBB) (BBxP) 12,803 - 11,102.08 = 1,700 .92154.62 6,122 - 6,075.00 = 47.00 4.27 6,301 - 6,210.75 = 90.25 8.20 6,996 - 6,912.00 = 84.00 7.63 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 in table I. Variety Block Truss I Puck I U 8 2 6 0 7 II 1.80618 III 1.70757 5.33982 II 1.61278 1.64345 1.50515 III 1.55630 1.44716 1 . 5 9 1 0 6 4.76138 4.59452 IV 1 .62325 1.64345 1.59106 T.85776 Totals " 6.61840 6.54024 - 6f39484 19.55348 B.B. I II III 1.34242 1.34242 1.38021 1.39794 1.43136 .1.34242 1.41697 1.49136 1.36173 1.36173 1.34242 1.54242 5.51706 5.60756 5.42678 4 .66505 4.17172 4.26806 4.04657 16755140 IFXBBT I II III ^1.44716' 1 . 3 9 7 9 4 h m 1.38021 1.39794 JUI6112 1.38021 1.44716 1.38021 1.43136 1.51851 1.41497 4.24304 4.13988 4.20758 4.36454 5.63894 5.76155 5*55485 16.95534 XBBXPT 5.44071 5.73261 5.81696 4.20514 4753842"" 4.23618 4.5105 4 16.99028 17.85305 17.11140 17.30634 17.77971 70.05050 I 1.34242 II 1.43136 III 1.43136 1.27875 1.36173 1.34242 1.47712 1.46240 1.47712 1.43156 1.55630 Analysis of variance.. SGurce P.P. S • S • Total 47 Varieties 3 Blots 2 Trusses 3 Var.xB&ock 6 Var.xTruss 9 Block xTruss 6 Error 18 6.7138$ 0.47270 0.00799 0.03256 0.02741 0.12148 0.00350 0.48320 x . _ 0.15756 2 1 . 7 6 0.00399 0.01085 3 . 3 2 0.00456 1.70 0.01349 5.03 0.00058 0.21 0.00268 -3.01 * 3.01 * 2.66 n.s, 2.46 * 2.66 n.s, Variance 0.0T215 0.00220 0.00184 0.00572 Bartlett's test for homogeneity of variance. Variety " 3 . S i _ „ w Puck 31 .99523 - 3I.86T54 = 0.13369 B.B. 22.85337 - 22.82907 = 0.o2430 (PxBB) 23.97730 - 23.95696 = 0.02034 (BBxP) 24.11875 - 24.05580 = 0.06295 Xs- =[(44x0.428l3)-11(0.08468+0.34420+0.26694+0.75762)] 2.3026= = (18.83772 - 15.98784)2.3026 = 6,56 Re quired =7.81 Table IV.Logarithm transformation of data i n table II, Variety Puck Block I II III TrussI 1 70757 1 .65321 1.71600 II III IV 1.54407 1.36173 IU27_815_ 1.34242 1.30103 X..5.8021 1.27875 1 .38021 1.49136 Totals 5.87281 5.69618 5.86652 5*07578 4.18455~4T02555 47T503217.43531 B.B • I II III 1.30103 1.30103 1.50103 3.90309 1 . 3 2 2 2 2 1.38021 1.32222 1.39794 1.36173 1.34242 "4.0246T""4.10209 1.39794 1.38021 J..39794 4.17609 5.41913 5.42318 ._5^ 3_6-3_6_l 16720592 (fxBB) T 1 . 3 4 2 4 2 II 1 . 3 0 1 0 3 4 . 0 2 3 6 6 3 . 9 H 2 3 1.27875 1.38021 U2S&2JL T738021 1 . 3 6 1 7 3 4 . 1 0 3 6 7 1 .38021 1.36173 Lt4624iL_ 4.20434 5.38159 5.40470 1 6 . 2 4 5 9 0 I II III T736T7T 1.41497 1.38021 Analysis Source of 4.15691 17.16044 Variance. 1 . 2 7 8 7 5 1.32222 1 . 5 2 2 2 2 1.38021 1.43136 h m 1 . 3 6 1 7 3 1 . 4 4 7 1 6 1 . 4 5 1 5 6 . 3 . 9 2 3 1 9 1 6 . 0 4 6 6 2 4.20951 4.24025 16.43893 16.77100 Total Varieties Blocks Trusses Var.xBloek Var.xTruss Block xTruss Error 47 3 2 3 6 9 6 18 S. S. 0.46026 0.08193 0.00085 0.05628 0.01850 0.22695 0.02856 0.05316 M.S. 0 . 0 2 7 3 1 0.00042 0 . 0 1 8 7 6 0 . 0 0 2 0 8 0 . 0 2 5 2 1 0.00476 0 . 0 0 2 9 5 5.38242 5 . 6 1 5 7 1 _ 5.5517I 1 6 . 5 2 9 8 6 6 6 . 4 1 6 9 9 Bartlett's test for homogeneity of variance Variety S . S. Variance "07027fcT~ 0 . 0 0 1 6 0 0 . 0 0 3 0 0 0.00262 Puck 25.63130 - 25.33250 = 0.29880 B.B. 21.90363 - 21.88598 = 0.01765 (PxBB) 22.02713 - 21.99410 = 0.03302 (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 XJ= 8.75/1.037 = 8.44 * Requiredx^.^ = 7.81 - 3 3 -The separate analyses f o r each temperature range are given i n tables V and V I I I . Table V.Number of flower buds formed on f i r s t four trusses of Bonny Best and i t s r e c i p r o c a l hybrids with Puck,at temperatures below 65°P. V a r i e t y B l o c k Truss I I I I I I _ I V Totals, Bbnny B. i ™ "" 22 25 26 23 96 I I 22 27 31 22 102 I I I ?A. 22 21. 22__ 9i 68 74 80 ^ 7 289 TPxBB)" (BBxP) I ~~ 28 24 24 27 11 25 25 28 33 I I I 25_ 24 26 78 72 76 86 I I I I I I 22 27 19 23 22 29 30 30 7 6 ^ 67 78 " W 222 213 234 249 103 111 312 " 93 109 115_ 317 918 31ocks '292 J322 Analysis of variance. ~~ m T s . "~ Source D . F . S. S. T o t a l 35 4 3 7.00 1 8 . 5 8 V a r i e t i e s 2 37 , 1 6 1.17 Trusses 3 81.00 27.00 5.60 Blocks 2 38.00 19.00 -Var.x Truss 6 137.50 2 2 , 9 1 5.35 Var.x Block 4 63.34 15.83 3.70 Truss x Block 6 28.66 4 . 7 7 1 . 1 1 Remainder 1 2 5 U 3 4 4 . 2 7 — J?JM 6.94 n.s, 4.76 * 3.00 * 3.26 * 3.00 n.s, Table V shows a) that differences between Bonny Best and the r e c i p r o c a l s can be considered due to chance,b) that differen-ces between trusses were real,and c) that there were s i g n i f i -cant differences i n the i n t e r a c t i o n s of v a r i e t y x truss and v a r i e t y x block. - 34 Truss I I J I I I IV 222 "213 234 249 3 -1 -1 -1 -1 3 -1 -1 -1 -1 3 -1 -1 -1 -1 3 Required I> 5$ = 4. 75 Table VI. Comparisons between primary truss e f f e c t s . D « s> « _ _ ___  JB\ -?0T /I2x3x3 = 8.3? 1.95 n.s, -66 f '/108 -40.3? 9.42 * - I 8 r /108 = 3.00 0.70 n.s, +78)* /108 =56,34 13.19 * Table VI shows the primary e f f e c t s of t r u s s e s . The number of flower buds formed on second trusses was s i g n i f i c a n t l y lower than the average number of flowers formed on other trusses, amd the number of buds on f o u r t h trusses was s i g n i f i c a n t l y higher. I t was recognized that the true primary truss 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 truss i n t e r a c t i o n . Totals f o r comparing the e f f e c t s of the i n t e r a c t i o n v a r i e t y x truss were obtained by summing over the blocks. Comparisons of genetic 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 detection of m a t e r n a l inheritance through Bonny Best cytoplasm, and ii.) i s a t e s t f o r vigor of the hybrids as compared to Bonny Best. The variances are shown i n table V I I . Table V I I . Comparisons of the e f f e c t s of the i n t e r a c t i o n v a r i e t y x truss at temperatures below 65°P. B B ( P x B B T (BBxP) variance F 68_7_4 80 67 78. 72 76 86 _. 76 67 78 9 6 _ ^ a r i a n c e f iT+1 +f+1 +1 -2 -2 -2""-5 +1 +1 +f"+T C-TBT= 4.~50 f .05" ns 72 i i ) +2 +2 +2 +2 -1 -1 -1 -1 -1 -1 -1 -1 (,-_j>l)=36.12 8.44 * 72 Required P 5$ = 4.75. - 35 -The maternal e f f e c t was not s i g n i f i c a n t as shown "by com-parison i).The P value f o r comparison i i ) i s s i g n i f i c a n t at the 5$ l e v e l of confidence,therefore,differences between the r e c i p r o c a l s and Bonny Best due to the condition of heterozy-g o s i t y were true ones.Thus differences between Bonny Best and the hybrids i n d i f f e r e n t trusses were s i g n i f i c a n t i n favour of the hybrids. The ana l y s i s of the data obtained from Bonny Best and the reciprocals,and excluding Puck,at temperatures above 65°P.is given i n table VIII,and none of the differences was s i g n i -f i c a n t . Table V I I I . Number of flower buds formed on f i r s t trusses of Bonny Best and i t s r e c i p r o c a l s with Puck,at temperatures ab-ove 6 5° P. Va r i e t y Block Truss I _II _ I I I . _IV__ Totals. Bonny Best I 20 21 25 25 91 II 20 24 23 24 91 III 21 _21_22__25_ 8 8 _ ~~ 60 66 70 74 270 "I" " 22 19 "24 24 89 II 20 24 23 23 90 III 24 18 22 29 24 - 56 6T 70 f£ 273 - - - - - — -Bloclcs. 3xPT " I " "23 19~"~~24 23 o~9 " 2.69 II 26 21 27 28 102 283 III 24 21_.,_25_ 2 j _ _ 2 7 _ ~ _ 2 i a _ _ 73 6? 76 78 288 199 188 216 228 831 - 3 6 -A n a l y s i s of variance. , Source D.F. S. S. jMxSTZLZ f _ _ 53l. T o t a l 35 """236775" ' 6.94 V a r i e t i e s 2 • 15.50 7.75 1.09 xxs» Trusses 3 104.97 34.99 4.66 4.76 ns. Blocks 2 8.66 4.33 - -Var.x Truss 6 28.94 4.82 1.82 3.00 ns. Var.x Block 4 17.84 4.46 1.68 3.26 ns. Truss x Block 6 29.12 4.85 1.83 3.00 ns. Remainder 12 31.72 2.54 . — _ ~ Since temperature ranges cons 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 desirable to combine the data obtained at the two temperature ranges. However i t has been shown that the date obtained from Puck cannot be included i n a combined an a l y s i s of variance with those from the other v a r i e t i e s . Therefore, there are two d i s t i n c t analyses. Further l i m i t a t i o n s are introduced by the f a c t that there i s no basis on which blocks i n the two houses can be i d e n t i -f i e d w i t h each other, thus an anal y s i s of variance f o r Puck data cannot separate a block 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 of the analysis f o r Puck data appears as fo l l o w s : Source ALsJ-Temperature 1 Trusses 3 Blocks w i t h i n temperatures 4 Temperature x Truss 3 Block x Truss w i t h i n temp. 12 The analysis of variance f o r Puck data at both tempera-tures gives s i g n i f i c a n t F values f o r temperature and truss primary e f f e c t s , as shown i n table IX. - 37 -Table IX. E f f e c t s of temperature on flower bud formation of Puck. Temperature Block Truss 1 2 3 4 Totals 5 5 ° - 6 5 ° P. 1 6 7 41 42 1 8 6 I I • 6 4 44 28 44 180 I I I 51 3 2 3 9 3 9 161 182 117 103 1 2 5 5 2 7 6 5° - 7 5 ° P . I 5 1 3 5 22 1 9 127 24 112 J5_i _. 126 ~ 7 4 " " ' 3 6 5 ' 199 892 I I 45 23 20 I I I 52 19 24 148 77 6 6 " Totals 330 194 1 6 9 Source To t a l Temperatures Trusses Blocks w i t h i n temperatures. Temp.x Truss Block x Truss w i t h i n temp. D.F. 2 3 1 3 S. S. 4 , 2 9 9 . 3 4 1,093.50 2,630.34 M.S.. _ 1,093.50 876.78 p 30 . 6 9 24.60 4.75 * 3 . 4 9 * 4 3 120.34 27.50 30.08 9 . 1 6 0.84 0 . 2 5 3.26 ns. 3.49 ns. 1 2 4 2 7 . 6 6 35.63 -E v i d e n t l y , the e f f e c t s of lower temperatures produced a marked increase i n the number of flower buds per c l u s t e r formed on Puck, and the number of flower buds was s i g n i f i -c a n tly higher i n f i r s t trusses. The data of the three remaining v a r i e t i e s can be combi-ned i n a s i n g l e analysis of variance, as i t i s shown by an E t e s t of the error mean squares calcu l a t e d i n tables V and V I I I . P = 4 . 2 7 = 1 . 6 8 ns. 2 . 5 4 Required E ( 1 2 d > f , . 5 / o ) - 2 . 6 9 - 38 -No block terms need to be considered i n the combined a n a l y s i s . I f the combined error term i s c a l c u l a t e d as the average of the two separate error terms from the two exper-iments, these error terms having been reduced already by the subtraction of the respective block terms, no f u r t h e r reference to blocks i s necessary ( 7 ) . Table X. E f f e c t s of temperature on flower bud formation of Bonny Best and i t s F1 r e c i p r o c a l hybrids with Puck. Temperature Truss Var. B.B. PxBB BBxP Totals 55°-65°F. 65°-75°B. 1 2 3 4 •1 2 3 68 ~ 7 8 76 222"" 74 72 67 213 80 76 78 234 o7... 86 96 289 312 317 918 60 66 73 199 66 61 61 188 70 70 76 216 270 76 273 288 228 ^831 559 585 605 1,749 Trusses 421 401 450 Analysis of variance. Source D»P».„. _ jLiL?,.-V a r i e t i e s 2 44•3? Trusses 3 184.48 Temperatures 1 105.12 Var.x Truss 6 106.22 Var.x Temp, 2 8,33 Truss x Temp. 3 1 .48 Pooled e r r o r 24 M,S« I _J2M 105.12 29«86 4,26 * 4.16 0 . 4 9 3.52 1.18 3.40 ns, 0,13 3.01 ns. Table X shows that there was a general s i g n i f i c a n t increase i n the number of buds per'inflorescence on Bonny 39 -Best and the r e c i p r o c a l hybrids as the temperature goes down from the higher to 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 relationships.. 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 experi-ments are shown, i n tables XI and XII f o r the cool and the warm rooms r e s p e c t i v e l y . These data represent the number of f r u i t s set on each p l o t expressed as percentages of the number of p o l l i n a t e d flowers. The angular transformation was used to analyse the data as shown i n the tables under the heading "angle". - 40 -Table XI. Number of seeded f r u i t s set at temperatures below 65°P.expressed as percentages of the number of p o l l i n a t i o n s made,and corresponding values obtained by means of the an-gular transformation. Rep.I Rep.II Rep.IlT Treatment $ angles. jo angle _ _| angle _ T o t a l s m 3 8 . 2 3 3 8 . 2 35.29 ' 3oTT" 50.00'""45.0" "119.7 ' PxBB 57 . 8 9 4 9.5 15 . 0 0 2 2 . 8 17 . 3 9 24.7 9 7 . 0 Px(PxBB) 5 9 . 0 9 50.2 45 . 0 0 42.1 57.14 4 9.1 141*4 Px(BBxP) 3 9 . 3 9 3 8 . 9 31.81 24.3 55 . 5 5 48,2 1 1 1 . 4 BBS 30 . 7 6 3 3.7 2 0 . 0 0 26.6 0 6 . (>0 0 . 0 6 0 . 3 BBxP 3 8 . 8 8 38.6 18.75 25.6 31.25 3 4 . 0 9 8 . 2 BBx(PxBB) 2 3 . 5 2 2 9 . 0 3 3 . 3 3 3 5 . 2 2 6 . 6 6 31.1 9 5 . 3 BBx(BBxP) 2 5 . 0 0 30.0 0 . 0 0 0 . 0 0 25 . 0 0 30.0 6 0 . 0 (PxBB)a 50 . 0 0 4 5 . 0 46.15 4 2 . 8 29.41 32.8 1 2 0 . 6 (PxBB)x? 70 . 0 0 5 6 . 8 3 3 . 3 3 3 5 . 2 60 . 0 0 50.8 1 4 2 . 8 ( P X B B ) X B B 66.66 5 4 . 8 44.44 41.8 66.66 5 4 . 8 1 5 1 . 4 (PxBB)x(BBxP) 50 . 0 0 4 5 . 0 70 . 7 2 5 7.2 66.66 54.8 157.0 ;BBXP}8 50 . 0 0 4 5 . 0 3 7 . 9 3 3 8 . 0 40 . 9 0 3 9 . 8 1 2 2 . 8 BBxPjxP 6 3.15 5 2 . 6 37.50 37.8 46.15 42.8 133.3 ,BBxP)xBB 6 9 . 2 3 5 6 . 3 50 . 0 0 45.0 52.14 4 6 . 2 147.5 . BBxP) x (PxBB ) _^21^&±^_66jl6 L J i A i . y i . 4 2 ^ 1 _ J M 6 § 8 . 8 5 6 5 . 7 5 2 6 . 2 1 8 9 0 . 7 Analysis of variance Source D.E. S • S • ~"M7sr Tota l 4 7 7 , 5 0 0 . 7 1 " " ' -Blocks 2 555.14 2 7 7 . 5 7 Treatments 15 4 ,405.56 2 9 3 . 7 0 E r r o r 30 2 ,540.01 84.66 3.27 3.32 n.s. 3.46 2.04 * In table XI i t i s seen that there were s i g n i f i c a n t d i f -ferences among treatments.Block primary e f f e c t s were non-s i g n i f i c a n t . S i m i l a r inferences can be drawn from the analysis of va-riance of the data i n table X I I . - 41 -Table X I I . Number of f r u i t s set at temperatures above 65° F. expressed as percentages of the number of p o l l i n a t i o n s made, and corresponding values obtained by means of the angular transformation. Rep.I Rep.II R e p . I l l Treatment.. _ fo „angle Jo angle.. f? ,__„an£le_ Totals Pft 40.00 3-9.2 "6'4.28 53."3 50.00 '4576 13775*" PxBB 54.54 47.6 35.71 ^6.7 56.25 4 8 . 6 132.9 Px(PxBB) 66*66 . 54 .7 35.71 36.7 52.94 46.7 1?8.1 Px(BBxP) 75.00 60.0 43.75 41.4 70.00 56.8 158.? BP® 69.23 56.3 72,72 58.5 57.14 49.1 163.9 BBxP 27.27 31.5 60.00 50.8 58.3? 49.8 132.1 BBx(PxBB) 27.27 31.5 46.15 42 .8 54.54 47 .6 121.9 BBx(BBxP) 44.44 41 .8 50.00 45,0 54.54 47 .6 134.4 ;PxBB)a • 60.00 50.8 70.00 56.8 6 1 . 1 1 51.4 159.0 .PxBB)xP 61.53 51 .6 44.44 41 .8 85.71 67.8 161.2 kPxBB)xBB 54.50 47 .6 62,50 52.2 78.57 62.4 162.2 ;PxBB)x(BBxP) 64,28 53.3 90.00 71.6 83.33 65.9 190.8 BBxP)a 66.66 54 .7 66,66 54.7 44.44 41.8 151.2 .BBxP)xP 53.84 47.2 75,00 60 0 50 00 45 0 152.2 BBxP)xBB 80.00 63,4 92.85 74.4 92.85 74.4 212.2 .BBxP)x(PxBB) 61 .55 51.6 75.35 58.9 46.15 42.8 15^3. 782.8 ~~ 83576 842.7 246*1.1 Anal y s i s of variance. „ .._ .... Source " B.P. S^S. M.S. _ f "5$? _____ T o t a l 47 4,721.22 -Blocks 2 133.88 66.94 * 1.02 3.32 n.s. Treatments 15 2,625.57 175.03 2.67 2.04 Er r o r 30 1,961.77 65.39 In order to combine the two sets of data i n one analysis which would show the e f f e c t s of temperature treatments,an P t e s t of the e r r o r mean squares of the two experiments was computed as given below. P = 8 4 . 6 6 = 1.29 n.s. 6 5 . 3 9 Required P 5 $ = 1.84 The n o n - s i g n i f i c a n t P value j u s t i f i e d the combination of data as shown i n table X I I I . - 42 -Table X I I I . Angular values of f r u i t s e t t i n g at low (11) and high ( T 2 ) temperatures. Treatment 11 ' T2. T1_. _J|£ ..._Tt_._ 3£ £o__al__, _ _ - 3 8 . 2 3 9 . 2 " " 3 6 . 5 53.3 45.0 4 5.0 2 5 7 . 2 PxBB 4 9 . 5 4 7 . 6 2 2 . 8 3 6 . 7 24.7 4 8 . 6 2 2 9 . 9 Px(PxBB) 50,2 5 4 . 7 4 2.1 3 6 . 7 4 9.1 , 4 6 . 7 2 7 9 . 5 Px(BBxP) 3 8 . 9 60.0 24.3 41.4 4 8 . 2 5 6 . 8 2 6 9 . 6 BB& 224.2 BBxP 3 8.6 31.5 25.6 50.8 34.0 49.8 230.3 BBx(PxBB) 29.0 31.5 35.2 42.8 31.1 47.5 217.2 BBx(BBxP) 30.0 41.8 0.0 45.0 30.0 47.6 194.4 (PxBB)S 45.0 50.8 42.8 5 6 . 8 32.8 51.4 279.6 (PxBB)xP 5 6.8 51.6 35.2 41,8 50.8 6 7 . 8 304.0 (PxBB)xBB 54.8 47.6 41.8 5 2 . 2 54.8 6 2 . 4 313.6 PxBB)x(BBxP) 45.0 53.3 57.2 71.6 54.8 65.9 347.8 BBxP)® 45.0 54.7 38.0 54.7 39.8 41.8 274.0 BBxPjxP 52.6 4 7 . 2 3 7.8 60.0 42.8 45.0 285.4 BBxPjxBB 56.3 63.4 45.0 74.4 4 6.2 74.4 359.7 BBxP)x(PxBB) .^ _____2 51___6 5 4 . 8 58 .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 A n a l y s i s ofjvarianjse. _ Source""' "3)717"~ Hs .S. M7S7''' 7" "g ~ 5$$ _~ "77" T o t a l 95 15,611.05 -Temperatures 1 3,389.13 3,389.13 17.70 3.39 * Treatments 15 5,285.73 352.38 1 . 8 4 1 . 8 4 * Temp.x Treat. 15 1,745.39 116.35 1.55 1.82 n.s. Pooled e r r o r 6 0 - 75.02 In table X I I I the P values f o r temperature and treatment primary e f f e c t s were found to be s i g n i f i c a n t when the t e s t term was the sum of the average error term of the two experi-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 to 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 block primary e f f e c t s and of a l l i n t e r a c -t i o n s i n which blocks take part,the P values would have been only s l i g h t l y changed,and conclusions would have been the same. Such pooling would have bg,en necessary since there i s no basis - 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 sets of comparisons between treatments were made s 1) a l l treatments were compared to P a , 2) a l l treatments were compared to BBa, 3) c r o s s - p o l l i n a t i o n s were compared to s e l l i n g s w i t h i n each v a r i e t y . Among the r e s u l t i n g 35 comparisons w i t h i n table XIII,eleven showed s i g n i f i c a n t differences,and are l i s t e d below, with differences and mean square?. PS - BBx(BBxP) P® - (PxBB)x(BBxP) m - (BBxP)xBB BB& - (PxBB)xP BB& - (PxBB)xBB BB& - (PxBB)x(BBxP) BBS - (BBxP)xP BB& - (BBxP)XBB BB& - (BBxP)x(PxBB) (PxBB)& - (PxBB)x(BBxP (BBxP)a - (BBxP)xBB Required variance at the 5 $ l e v e l = 300.08 The above comparisons show at the 5% l e v e l of confidence that;a) compared to Pa,Bonny Best plants p o l l i n a t e d with p o l l e n from the (BBxP)f, gave the lowest f r u i t set.In the same sfct of comparisons, (BBxP) Fi p o l l i n a t e d w i t h Bonny Best gave s i g n i f i -c a ntly higher f r u i t set,and so di d the hybrid (PxBB)F, when 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 . b) compared to BBa,both hybrids set a higher number of 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 . = +62.8 328.65 - - 9 0 . 6 684 .03 =-102.5 8 7 5 . 5 2 = - 7 9 . 8 530.67 = - 8 9 . 4 666 .03 =-123.6 1273.08 = - 6 1 . 2 312.12 =-135 .5 1 5 3 0 . 0 0 = -61.2 312 . 12 = - 6 8 . 2 3 8 7 . 6 0 = - 8 5 . 7 6 1 2 . o 4 - 44 -c) i n comparisons of treatments w i t h i n each v a r i e t y , i ) (PxBB)- had heavier f r u i t set when c r o s s - p o l l i n a t e d w i t h i t s reciprocal,and I i ) (BBxP)F, when crossed with Bonny Best. At high temperatures a l l f r u i t s produced contained seeds. At low temperatures parthenocarpic f r u i t s occurred as shown i n table 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 parthenocarpic f r u i t s , a n d percentages of partheno-carpy occurring on the four tomato l i n e s at low temperatures. No, of p o l - Nbuof No,of partheno- fo of par-V a r i e t y l i n a t i o n s f r u i t s set carpic f r u i t s t heno c amy Puck 290 119 0 0 Bonny Best 199 67 19 28.35 (PxBB) 223 129 7 5.42 (BBxP) 237 121 5 4.13 Parthenocarpic f r u i t s d i d not develop on Puck plants 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 pollinations,whereas Bonny Best bore the highest 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 to the number of days occurring between p o l l i n a t i o n and maturation as seen i n table XV were subjected to analysis of covariance, as shown i n table XVI,in order 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 closeness of the c o r r e l a t i o n between the two variables.The 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 . Regression c o e f f i c i e n t s were ca 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 values i n d i c a t e that 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 maturation period corresponding to an in c r e a -se of one seed i n f r u i t content.Under the conditions of the ex-periment such a decrease had an o v e r a l l average value f o r the four v a r i e t i e s of -0.048 days per seed.Coefficient 2) was a measure of the decrease i n seed content which can be expected f o r an increase of one day i n the length of the maturation period. Regression c o e f f i c i e n t s b were ca l c u l a t e d f o r each y .x v a r i e t y and are given as f o l l o w s : Puck = -0.024 Bonny Best = -0.082 ( P X B B ) F I = -0.075 (BBxP)n = -0.034 These values show that 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 varieties.How-ever, because of v a r i e t a l differences 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 regression both parents matured f r u i t s e a r l i e r than the hybrids.The average _ 46 -length of the maturation period f o r each v a r i e t y was found to he as f o l l o w s : Puck = 67;Bonny Best = 71;(PxBB) n = 76; (BBxP)F, = 74. days. Table XV. Number of seeds per f r u i t , a n d number of days to ma-t u r i t y i n each of the four tomato l i n e s at temperatures above 65°P. Puck Seeds .Pays ~1$8~' 63 72 17 70 80 52 23 92 107 126 98 45 40 159 104 151 182 154 166 _11_L 66 67 64 64 64 87 61 66 62 66 76 68 67 67 67 72 70 75 63 B»B» Seeds .Days 153 6*8 123 148 132 102 271 140 87 35 43 171 103 106 71 111 67 71 76 74 62 68 61 83 83 64 64 68 77 83 TPX": Seeds " 279' 194 208 175 143 2? 165 227 217 161 194 125 156 67 96 29 Ft Bays """6'q 70 64 77 70 76 81 76 74 66 65 73 79 94 68 95 CBBXPX-, Seeds Days 144' ' 70" 1 0 5 20 284 207 185 86 40 59 30 55 40 115 58 31 237 308 72 74 74 73 75 77 67 76 71 71 79 77 79 82 73 66 64 64 96 Totals 2049 1355 Means 102.4 6 7 . 7 '1796"" TQST ' 119.7 71.2 2458''" f 197" 153.6 74.I 2303 "1408"" 121.2 74.1 Table XVI. Analysis of covariance of data from table XV, Source" I). P. , SSx Spxy _ SSy Total 69" " 350,741 .78 -12,923.62 4,323.28 V a r i e t i e s 3 23,672.98 3,088.60 578.36 Within Var. 66 327,068.80 -16,012.22 3,744.92 Regression 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. x = -0.048 bx.y = -4.275 r = -0.457 x.y - 47 -C a l c u l a t i o n of adjusted v a r i e t y means. Experiment mean = x = 124.50 Var. X X-x b(X-x) y adj.y Puck" 102.45 ^22T05 -U05" 67". 75~~'66~.W B.B. 119.73 - 4.77 -0,02 71 .26 71 .24 (PxBB)f/ 153.62 29.19 1 .39 74.81 76.20 (BBxP)F, 121 .21 3.29 0.15 74.10 74.25 Analysis of covariance f o r each v a r i e t y . . V&r,__ Puck B.B. (PxBB)F, (BBxP)f( D.F. 19 14 15 18 SSx ' 51 ,070.95" 45,360.94 76,595.75 154,041.16 Puck h = -0.024 B.B. b y.x = -0.082 (PxBB) P ( by.x = -0.073 (BBxP)* ^y .x = -0.034 SSy •1 ,2 40.7 5 691 .75 •3,734.93 822.94 •5,648.12 1,260.44 •5,388.42 969.79 B. 0ytologic_al Exp eriment s. a) Microsporogenesis. Meiosis does not occur simultaneously i n a l l p o l l e n mo-ther c e l l s of an anther.Metaphase,anaphase,and telophase of the homotypic d i v i s i o n often are contemporaneously taking place i n m a t e r i a l d i v i d i n g under normal temperature conditio The most outstanding deviation from the patterns of re l a r meiosis observed i n microsporogenesis under low tempera' tures was a greater spread of the meiotic/bhases occurring a - 48 -any one time w i t h i n the same anther.It was noted that some of the p o l l e n mother c e l l s undergoing meiosis i n the lower tempe-rature range were delayed to a greater extent than under more customary conditions of temperature.Thus,in material of the same anther,chromosomes of c e l l s s t i l l i n early telophase I I were seen along with p o l l e n tetrads i n which meiosis had a l -ready heen completed,and maturation of p o l l e n had progressed, as shown hy the red c o l o r a t i o n of acetocarmine s t a i n i n g of the w a l l s . During the experiments,diurnal temperature f l u c t u a t i o n s were kept as c l o s e l y as possible w i t h i n a 10°F range,the maxi-mum occurring i n the noon hours,especially i n sunny days,Thus, i n the cool house temperatures were normally below 60°P.and went over 60°P. only a few hours on some days. I t i s known that 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 meiotic stages,though more i s known about e f f e c t s of high 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 hypothesis of d i f f e r e n t temperature requirements of meiotic phases.Pro-bably 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 highest temperatures of the 55-65" P. range a f t e r the noon hours, were delayed u n t i l minimum temperatures required f o r the process were attained again 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 . In the meantime,cells i n which meiosis 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 reasing the gap occurring between ea r l y and l a t e f o r -- 49 -mine; t e t r a d s . Such a pattern nrobably r e s u l t s i n enhanced competitive e f f e c t s when starch synth«si s i n the maturing microspores ±s l i m i t e d by short carbohydrate "tuTvol i e s . In general, low temperatures p r o d u c t onlv a r e l a t i v e l y low increa.se of abnormal d i v i s i o n s , and the occurrence of ab-nor m a l i t i e s was not great enough to explain the high rate of p o l l e n degeneration. The most evident abnormality was the formation of bridges at anaphase of the heterotypic d i v i s i o n . In one instance a. bridge was seen between two of the four n u c l e i o r i g i n a t i n g from the homoiypic d i v i s i o n , Brid.ees are l i k e l y to produce gene du 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 of 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 . In one instance a supranumerary small nucleus was noted, probably formed from lagging chromosomes. I r r e g u l a r p a i r i n g at nropha.se I often resulted i n forma-t i o n of s i s t e r n u c l e i containing reduced or supranumerary chromosomes. The tomato i s s e n s i t i v e to the e f f e c t s of chromo-somal imbalance, and any abnormality may account f o r reduced p o l l e n production. Because of low frequency and of lack of consistency i n the occurrence of abnormalities at any one time, no attempt was made to 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 of p o l l e n produced i n the warm house and e s t i -mated by means of the acetocarmine s t a i n i n g procedure i s g i -ven i n table XVI. Table XVI. Percentages of v i a b l e p o l l e n of Puck,Bonny Best, and t h e i r r e c i p r o c a l hybrids,formed, at temperatures above 65°P. Bate December 11 13 January 15 19 21 23 25 27 29 31 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. (PxBB)^ (B3x?)._7 83 98 99 95 98 97 86 96 96 47 96 99 78 92 97 88 98 75 83 92 96 84 88 96 96 93 90 75 94 88 91 98 97 92 99 99 87 91 97 85 95 93 85 93 97 94 97 93 90 92 98 88 79 99 96 98 94 96 92 98 95 96 99 99 28____. 9_2-i-~,. ' 1"910 2076 2090 86.81 98.85 95.00 49 20 24 Percentages of normal appearing p o l l e n were high and co n s i s t e n t l y so through the duration of the whole experiment. In general Bonny Best had lower percentages of v i a b l e p o l l e n than Puck and both the hybrids,Bonny Best also had the wider-range ,while the hybrids averaged the highest means of v i a b l e - 51 -pollen, produced at the warm temperatures. The p o l l e n produced i n the cool house gave the data shown i n table XVII. Table XVII. Percent of v i a b l e p o l l e n of Puck,Bonny Best,and t h e i r r e c i p r o c a l hybrids,formed at tempe-ratures below 65°P, Blower Puck B.B. (PxBB)F, (BBxP)-, 1 3 8 15 26 2 9 2 14 4 3 1 37 11 28 4 25 1 13 36 5 0 74 1 10 6 23 0 13 17 7 12 3 24 44 8 8 77 9 26 9 22 0 3 15 10 __ _ 1 6 _______ Totals 108 203 109 229 Means 10.8 20 .3 10 .9 2 2 . 9 Ranges 25 77 23 40 In general the percentages of normal,viable p o l l e n were exceedingly low when compared to the r e s u l t s f o r p o l l e n pro-duced at the higher temperature range. Ranges i n v i a b i l i t y were greater i n a l l v a r i e t i e s grown at low temperatures as compared to r e s u l t s at the higher tem-peratures .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 parents were of the same v a r i e t y , t h a t i s Puck and (PxBB) f ,and Bonny Best and (BBxP) f i .These means were sub-jected to t t e s t s as f a l l o w s j Puck x 10.8 S.S. 795o60 Var. 88.40 Var.- 8,840 (PxBB) r 10.9 394.90 43.87 4.387 SE_, =^1'5.227 = 3.63 D t = 0.1 = 0 . 0 2 7 n.s. Required t ( l 8 d.f,,. 5 9.) 3 . 6 3 = 2.101 i i ) Bonny Best x 20.3 S.S. 8 , 7 3 2.10 Var. 970.23 Var.-r 97.023 1 , 2 8 2 . 9 0 1 4 2 . 5 4 1 4 . 2 5 4 SEg = 1 1 1 . 2 7 7 = 1 0 , 5 4 ~ 2___6_ - 0 . 2 4 6 n.s. T6.54 t values are not s i g n i f i c a n t showing that differences between means of r e l a t e d v a r i e t i e s could have been due to chance, thus suggesting the p o s s i b i l i t y of transmission i n maternal fashion of the production of p o l l e n at low temperatures. c) P o l l e n germination experiments, Experiments on p o l l e n germination j n j y i t r o encountered h i g h l y inconsistent r e s u l t s , f o r which no reason was obvious. Such inco 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 table XVIII, and the blank space corresponding to the 20°C. ma t e r i a l on the f i r s t date was due to l o s s of the ma t e r i a l because of imperfect sealing of the w e l l - s l i d e s , - 53 -i Table XVIII. Percentages of p o l l e n grains produced at high temperatures , germinated at 10°, 15°,,and 20° C. ~I?eb727 Mar .3™ _P B < B i_ _ _P__ B • B_4_ 4 20 """"15 ~ ' 10 6 34 10 11 19 29 14 18 "8.1 ;?7T6"i'3~'~13~ 1 5° 0. 1 24 28 6 21 27 7 12 35 21 18 2 22 36 7 12 44 9 11 45 16 26 3 16 20 14 12 45 6 13 39 21 25 . 4 11 26 Ave. 18 .2 "27 T5~ 15 38.6 ~" 7."3 "1*2 "3976^1_T.3" ~23~ 20° C. 1 10 17 48 8 16 24 17 15 2 12 15 42 11 15 26 24 18 3 11 12 42 7 16 27 22 24 Ave. 11 14 44 8.6" 15".6" 25.6" 21 19 By i n s p e c t i o n of table XVIII extreme v a r i a b i l i t y i n trie average germination percentages obtained on d i f f e r e n t dates i s c l e a r l y noticeable.However,two trends emerge from these data: a) there was an increase i n percentages of germinated p o l l e n w i t h increasing temperatures.This increase occurred 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. l e v e l s . b) under the conditions of t h i s experiments,at 10° and 15° G. puck p o l l e n produced at high temperatures averaged lower ger-mination percentages than Bonny Best did i n four out of f i v e occasions;at the temperature of 20°C.each of the two v a r i e t i e s was the best i n two out of four t r i a l s . On February 24,differences i n germination 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 Temu Count ®eb°U""~Feb.l8 ~~ Fe¥.24~"" I—..'. P .B.B. P B..B. P B.B. 10° G. 1 11 26 6 6 "20 7 2 6 23 4 11 21 10 3 12 25 2 • 7 20 9 4 a 28 Ave. ~ 9."5 28 ' 4 8 20.3 8.6" - 54 -Bonny Best at i t s lowest v a l u e . E v i d e n t l y , i f the same environ-mental conditions were a c t i n g on both v a r i e t i e s , t h e y were af-f e c t i n g Bonny Best to a greater 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 inconsistency was thought to be ac-t i n g on the p o l l e n before samples were taken f o r germination, that 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 observations on p h y s i o l o g i c a l age the p o l l e n at.sampling time are given i n tableXIX. Table XIX. Percentages of p o l l e n germination from flowers at d i f f e r e n t stages of anthesis. Bate Anth. n + 1 ^ ? fi r l i r i + ? o n n£ B e S t March 6 1 3 2 2 . 5 7 2 4.5 2 2 5 2 2 23.5 1 0 7 8.5 3 24 2 0 2 2 . 0 5 6 5.5 4 14 16 15.0 . 6 5 5 . 5 5 2 7 28 2 7 . 5 March 7 1 24 15 19.5 1 0 0.5 2 1 6 21 18.5 1 2 1.5 3 30 26 28.0 16 14 15.0 March 15 1 11 13 12.0 13 12 12,5 2 15 18 16.5 14 13 13.5 3 24 22 23.0 10 7 8.5 4 14 12 13.0 7 8 7.5 Percentages of germination were c o n s i s t e n t l y higher f o r Puck p o l l e n taken from blossoms i n intermediate stages of an-th e s i s , and quic k l y declined on both sides of the optimum.Bon-ny Best averaged very low percentages i n two out of three t r i a l s , i n which highest values 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 trend was reversed. These inconsistencies give f u r t h e r support to the hypo-t h e s i s that presumably s i m i l a r environmental conditions 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 of Puck and Bonny Best p o l l e n , f o l l o w i n g dehiscence of the anthers. During the experiments studying p o l l e n germination i n v i t r o . i t was noted that some p o l l e n grains produced two tubes instead of the normally occurring s i n g l e tube,as i l l u s t r a t e d i n plates I and II.Such grains were seen very i n f r e q u e n t l y , and attempts to s t a i n the n u c l e i w i t h i n the growing tubes with 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 grains were observed at two hour, intervals,two of them were seen growing toward each other at f i r s t , t h e n meeting In an oval enlargement,as seen i n pl a t e III,from w h i c h , ! i n a l l y , a s i n g l e tube emerged,as seen i n plate IV.Observations were repeated to a s c e r t a i n the occurrence of anastomosis.However,even the use of a micromanipulator d i d not succeed i n increasing the frequency of growing points meeting at the r i g h t stage,and when tubes met,frequently one of the two burst,or they went ,onP under the other.Nonetheless,by means of micromanipula-t i o n s i t was possible to a s c e r t a i n on several occasions what appeared to be the f u s i o n of the tubes,though no conclusive evidences to support the occurrence., of complete anastomosis and the mixing of 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 increase i n number of flower buds produced by expo-sures of plants to temperatures below the optimum range of 6 5 ° to 7 5 " F. was found to 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 1s (11) results.The former reported that s i m i l a r e f f e c t s were obtained i n experiments i n which seedlings exposed to temperatures of 14"C. were compared to seedlings grown at 25°C.In those experiments,aftex the t r e a t -ments at seedling stage,plants were presumably kept i n uniform environmental conditions u n t i l flower buds were counted,Lewis concluded that the s e n s i t i v e period f o r temperature e f f e c t s showing up to f i f t h c l u s t e r s occurs between the 8th day a f t e r emergence and the formation of the f i r s t i n f l o r e s c e n c e . However,in the present i n v e s t i g a t i o n seedlings were kept i n a uniform 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 nflorescences were already formed.Despite thjs uniformity of i n i t i a l treatments,later exposures to d i f f e r e n t i a l temperatu-res produced e f f e c t s s i m i l a r to those described i n Lewis' report,showing that the s e n s i t i v e temperature stages extend beyond the period of f l o r a l induction 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 inflorescence Furthermore,at the lower temperature range of 5 5 ° to 65"F., i f flower bud counts were repeated at long i n t e r v a l s on the same clusters,increased values were f o u n d , p a r t i c u l a r l y where there was l i t t l e or no f r u i t s e t t i n g . These observations suggest that temperatures below the - 58 -optimum range f o r tomato growing produce s i g n i f i c a n t increases i n the numbers of flowers per inflorescence,and that such tem-peratures are e f f e c t i v e at any stage of development of the inf l o r e s c e n c e . The purpose of the p o l l i n a t i o n experiments was to gain 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 four v a r i e t i e s under investigation,and to as c e r t a i n any nhange i n those relationships,suspected of occurring under d i f f e r e n t i a l temperature treatments. In previous work i t had been reported by Daubeny that the a p p l i c a t i o n of Puck p o l l e n to Bonny Best stigmas at cool tem-peratures f a i l e d to f e r t i l i z e the ovules;the f r u i t s produced were found to be Largely parthenocarpic.Since p o l l e n used was produced i n the warm house and supposedly viable,these f i n d -ings appear to detract from the e a r l i e r hypothesis that gene-t i c d ifferences i n p o l l e n v i a b i l i t y are the basis f o r the differences i n f r u i t s e t t i n g at low temperatures. The present i n v e s t i g a t i o n was aimed at substantiating these observations,and extending them to the P1 hybrids.Thus, behaviour of po 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 at the two tem-perature levels.Eo attempt was marie to use p o l l e n produced, at low temperatures since i n s u f f i c i e n t amounts are produced by Bonny Best under such conditions. The improvement of tecbnicmes f o r commercial production - 59 -of P1 hybrid seed has proven i t s e l f to be a valuable means of providing growers with the desired seed,whilst other time-r 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 that 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 with other varieties.The 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) F, i s p o s s i b l y to 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 stressed by inferences drawn from, the regression analy-ses. I t i s evident that any cause producing a reduction i n seed content of tomatoes w i l l r e s u l t i n an increase of the number of days necessary f o r f r u i t maturation. When low spring temperatures are the l i m i t i n g f a c t o r to the production of early y i e l d s , f r u i t s with poor seed content 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 set e a r l y i n the season.Furthermore,varieties on which low tempe-ratures are bound to produce parthenocarpy or d r a s t i c reduc-t i o n s i n number of seeds, appear to be unsuited to growing areas characterized by short seasons because low temperatures are l i k e l y not only to delay early yields,but also to hinder the maturation of l a t e f r u i t s . Observations on parthenocarpy confirmed previous reports 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 -smaller than those found by other workers,probably owing to a difference i n technique,whereby p o l l e n a p p l i c a t i o n s were repeated twice at one-day intervals.Such a technique did pos-s i b l y increase the percent of f r u i t s set,and from observation of plants i t was possible to see that i n general the develop-ment oflT seeded fru.its had p r i o r i t y over parthenocarpic f r u i t s , which often abscissed as undeveloped ovaries. C y t o l o g i c a l Experiments. As already pointed out by Maheshwari (32) and by Hewlett (18),when carbohydrates are i n short supply during the proces-ses of p o l l e n maturation,more or leas large amounts of p o l l e n grains are bound to become -on-functional,or i n extreme cases, to degenerate a f t e r meiosis has been completed.Rates of normal meiosis were not found to be influenced by low temperatures to so great an extent as to account f o r extensive p o l l e n degene-r a t i o n such as that occurring i n Bonny Best at low temperatu-res . Under the conditions of t h i s experiment,shortage of carbo-hydrates might have been due to low photosynthesis.Glass walls of the greenhouse cut down l i g h t c o n s i d e r a b l y , p a r t i c u l a r l y during periods of 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 providing l i g h t of low energy was probably only 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 acting 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 reducing the rate of photosynthesis,or producing narrow res-- 61 -piration/photosynthexic ratios.Whatever the cause of carbohy-drate shortage,the occurrence of some p o l l e n mother c e l l s com-p l e t i n g meiosis considerably e a r l i e r than others would give the e a r l i e r forming tetrads an. advantage i n n u t r i t i o n a l competition w i t h respect to l a t e forming ones. As a possible alternate explanation to p a r t i a l p o l l e n de-generation the hypothesis can be advanced that 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 conditions of short n u t r i e n t supplies.There was no d i r e c t e v i -dence that such a phenomenon occurred. Differences 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 characters,Puck probably i s able to carry on photosynthesis at a greater rate than Bonny Best.Such characters are undoubtely g e n e t i c a l l y con-t r o l l e d and data i n table XII showing marked differences between r e c i p r o c a l P1 hybrids suggest inheritance i n a maternal fashion. However,more c o n t r o l of environmental conditions i s necessary to reduce the large v a r i a b i l i t y showing up i n experiments of t h i s type,and to increase the r e l i a b i l i t y of conclusions there-from. Lack of c o n t r o l of the environmental conditions 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 plants were grown are rather u n s a t i s f a c t o r y when a very precise c o n t r o l of the flower microenvironment i s required, f i r s t of a l l , l i g h t i s cut down to a. large extent by the glass, - 62 -and secondly,shadowing,particularly i n sunny days,varies from place to place during the day,owing to the r e l a t i v e p o s i t i o n of the sun with respect to other plants,walls,and greenhouse supporting s t r u c t u r e s . Temperatures change i n d i f f e r e n t places at very short distances mainly i n r e l a t i o n to the p o s i t i o n of the heating pipes,and to the distance from the glass walls.Further v a r i a -b i l i t y i s introduced by sun heat i n periods of clear- weather or a l t e r n a t e cloudiness . 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 heating 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 contributing 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 cooling 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 s a t i s f a c t o r y , since to obviate to the d i f f i c u l t y of having p o l l e n of the same age,sampling should be done on large masses of grains c o l l e c t e d and mixed from a large number of flowers.In 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 his:a) anthesis i s s c a l a r i n tomatoes,thus reducing the number of flowers i n blossom at any one time,so that c o l l e c t i o n of large samples requires more plants than i t was possible 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 destroying sampled flowers reduced furthermore the number of flowers a v a i l a b l e on successive dates. - 63 -There are two hypotheses which can he advanced from the r e s u l t s of these experiments; a) that differences i n p o l l e n v i a b i l i t y between tomato var-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 characters,such as a b i l i t y to make carbohydrates •available to the maturing tetrads i n the anthers,even under unfavorable en-virormental c ond i t i ons.j b) that 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 act i o n of several 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 better control, of both the f l o r a l micro- and macro-environments • - 64 -SUKMARY AN CONCLUSIONS Greenhcmse and cytologycal 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 hybrids were performed to a s c e r t a i n s u i t a b i l i t y of Puck i n a breeding programme aiming at producing new tomato v a r i e t i e s .for the growing regions of the North American, continent, which are characterized bv low spring temperatures, and/or short season. B r u i t s e t t i n g and ear l i n e s s i n the tomato depend upon several f a c t o r s , and were studied i n an experiment conducted i n greenhouses where plants were grown at two temperature ranges, namely 55°to 65°,and 65°to 75°P.. The l a t t e r were considered optimum temperatures f o r growth and development of tomato p l a n t s . a) Greenhouse Experimentsj 1) E f f e c t s of temperature on flower 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 r e l a t i o n s h i p s ; 3) E f f e c t s of seed set on earli 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 of temperature on microspore development; 2) E f f e c t s of temperature on p o l l e n v i a b i l i t y ; 3) Germinability of p o l l e n produced at normal temperature. Temperatures below the optimum range f o r the tomato were found to increase s i g n i f i c a n t l y the number of flowers produ-ced on a l l v a r i e t i e s . At low temperatures the increase produ-ced on the hybrids compared to that occurring on Bonny Best was s i g n i f i c a n t . At the lower range of temperature a s i g n i f i c a n t reduction 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 clear-cut trend revealed 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 increase i n number of f r u i t set on P1 hybrids when c r o s s - p o l l i n a t e d w i t h any one of the other v a r i e t i e s i n the experiment,than when self-pollinated,These r e s u l t s suggest a reduction of s e l f -c o m p a t i b i l i t y i n the hybrids produced by temperatures below the optimum,and l i m i t the convenience of P1 hybrids f o r com-mercial production. The number of days between p o l l i n a t i o n and maturity 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 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 In which low temperatures pro-duce reduction 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 pro^ duction i n areas where cool spring temperatures are usual,and wherever growing seasons are short. Low temperatures,possibly i n t e r a c t i n g with low l i g h t i n t e n s i t y and short photoperiod,appear to 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 reduc-t i o n of the nut r i e n t supply a v a i l a b l e to the maturing p o l l e n tetrads.Low temperatures were found to delay completion of meiosis over a longer than usual period of time,and t h i s delay was believed to enhance the ef f e c t s of n u t r i t i o n a l competition among tetrads maturing i n conditions of nutrient 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 high 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 at low temperatures s i m i l a r i t i e s between - 66 -means of Puck and (PxBB) F ) ,and Bonny Best and (BBxP) F / suggested an extranuclear inheritance of the character "production 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 considered conclusive. 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 un-expected v a r i a b i l i t y i n germination percentages.Owing to i n -consistency of r e s u l t s no d e f i n i t e trend emerged from those observations.This i n d i c a t e s the need f o r more close c o n t r o l of the flower microclimate i n experiments of t h i s type. In the F1 hybrids the increase i n number of flowers formed at low temperatures i s p a r t i a l l y counterbalanced by a reduction 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 generation hybrids. Puck produces a higher number of flowers,has no reduction of c o m p a t i b i l i t y , a l o n g with consistent seed set at low tempe-ratures , therefore i s to be considered a valuable source of germ plasm i n o u t l i n i n g a breeding programme. APPENDIX GOOD HOUSE Block I (PxBB)xBB (PxBB)xP (BBxP)xBB (PxBB)x(BBxP) (BBxP)® (BBxP)xP BB® (BBxP)x(PxBB) PxBB (PxBB)® P® BBxP BBx(PxBB) BBx(BBxP) Px(PxBB) Px(BBxP_)_ Block I I P® BBx(BBxP) PxBB BBxP Px(BBxP) (BBxP)x(PxBB) (BBxP)xP (BBxP)® BBx(PxBB) ( P K B B ) ® Px(PxBB) (PxBB)xP (PxBB)xBB (PxBB) x( BBxP) BBxP)xBB Block I I I (PxBB)® (BBxP)® Px(BBxP) BBxP BB® (BBxP)xP (BBxP)xBB PxBB (PxBB)x(BBxP) Px(PxBB) BBx(PxBB) P® (PxBB)xP (BBxP)x(PxBB) (PxBB)xBB - 68 -APPENDIX WARM HOUSE Block I (BBxPyiBB™ (BBxP)® (PxBB)xBB PxBB Px(BBxP) BBx(PxBB) BB® (BBxP)x(PxBB) BBx(BBxP) P® (PxBB)x(BBxP) (BBxP)xP (PxBB)xP BBxP (PxBB)® Block II BB® (PxBB)® PxBB Px(PxBB) BBx(BBxP) -Px(BBxP) B B * ? ( B B x P ) x P P ® (BBxP)® (B£xP) x B B JBlock III BBxP Px(PxBB) BB® BBx(PxBB) (PxBB)® PxBB (BBxP)x(PxBB) (PxBB)xP BBx(BBxP) (BBxP)xP P® (PxBB)xBB fx(BBxP) (PxBB)x(BBxP) (BBxP)xBB (BBxP)® - 67 sb-BIBLIOGRAPHY 1. Bishop,C.J, 1954. A stamenless male s t e r i l e tomato.Am.J.Bot. 41* 540-42. 2. Bohn,C.V. 1955. 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