{"Affiliation":[{"label":"Affiliation","value":"Land and Food Systems, Faculty of","attrs":{"lang":"en","ns":"http:\/\/vivoweb.org\/ontology\/core#departmentOrSchool","classmap":"vivo:EducationalProcess","property":"vivo:departmentOrSchool"},"iri":"http:\/\/vivoweb.org\/ontology\/core#departmentOrSchool","explain":"VIVO-ISF Ontology V1.6 Property; The department or school name within institution; Not intended to be an institution name."}],"AggregatedSourceRepository":[{"label":"Aggregated Source Repository","value":"DSpace","attrs":{"lang":"en","ns":"http:\/\/www.europeana.eu\/schemas\/edm\/dataProvider","classmap":"ore:Aggregation","property":"edm:dataProvider"},"iri":"http:\/\/www.europeana.eu\/schemas\/edm\/dataProvider","explain":"A Europeana Data Model Property; The name or identifier of the organization who contributes data indirectly to an aggregation service (e.g. Europeana)"}],"Campus":[{"label":"Campus","value":"UBCV","attrs":{"lang":"en","ns":"https:\/\/open.library.ubc.ca\/terms#degreeCampus","classmap":"oc:ThesisDescription","property":"oc:degreeCampus"},"iri":"https:\/\/open.library.ubc.ca\/terms#degreeCampus","explain":"UBC Open Collections Metadata Components; Local Field; Identifies the name of the campus from which the graduate completed their degree."}],"Creator":[{"label":"Creator","value":"Stanfield, Barrie","attrs":{"lang":"en","ns":"http:\/\/purl.org\/dc\/terms\/creator","classmap":"dpla:SourceResource","property":"dcterms:creator"},"iri":"http:\/\/purl.org\/dc\/terms\/creator","explain":"A Dublin Core Terms Property; An entity primarily responsible for making the resource.; Examples of a Contributor include a person, an organization, or a service."}],"DateAvailable":[{"label":"Date Available","value":"2011-09-06T18:03:58Z","attrs":{"lang":"en","ns":"http:\/\/purl.org\/dc\/terms\/issued","classmap":"edm:WebResource","property":"dcterms:issued"},"iri":"http:\/\/purl.org\/dc\/terms\/issued","explain":"A Dublin Core Terms Property; Date of formal issuance (e.g., publication) of the resource."}],"DateIssued":[{"label":"Date Issued","value":"1965","attrs":{"lang":"en","ns":"http:\/\/purl.org\/dc\/terms\/issued","classmap":"oc:SourceResource","property":"dcterms:issued"},"iri":"http:\/\/purl.org\/dc\/terms\/issued","explain":"A Dublin Core Terms Property; Date of formal issuance (e.g., publication) of the resource."}],"Degree":[{"label":"Degree (Theses)","value":"Master of Science - MSc","attrs":{"lang":"en","ns":"http:\/\/vivoweb.org\/ontology\/core#relatedDegree","classmap":"vivo:ThesisDegree","property":"vivo:relatedDegree"},"iri":"http:\/\/vivoweb.org\/ontology\/core#relatedDegree","explain":"VIVO-ISF Ontology V1.6 Property; The thesis degree; Extended Property specified by UBC, as per https:\/\/wiki.duraspace.org\/display\/VIVO\/Ontology+Editor%27s+Guide"}],"DegreeGrantor":[{"label":"Degree Grantor","value":"University of British Columbia","attrs":{"lang":"en","ns":"https:\/\/open.library.ubc.ca\/terms#degreeGrantor","classmap":"oc:ThesisDescription","property":"oc:degreeGrantor"},"iri":"https:\/\/open.library.ubc.ca\/terms#degreeGrantor","explain":"UBC Open Collections Metadata Components; Local Field; Indicates the institution where thesis was granted."}],"Description":[{"label":"Description","value":"Effects of day\/night temperature regimes ranging from 45\/40 to 90\/75\u00b0F on growth and development of Dark Skin Perfection peas were studied in controlled-environment cabinets. Light intensity was about 1500 foot-candles and the photoperiod was 16 hours. Rate of plant development, in terms of nodes produced per day, increased steadily as the average temperature increased. Rate of stem elongation, however, was most rapid at 70\/55\u00b0F; and plant height was greatest at 60\/50\u00b0F. On a dry matter accumulation per day basis, vine growth decreased above and below a temperature optimum which shifted from 70\/60 to 60\/50\u00b0F in the course of plant development. Tillering was most prolific at the lower temperatures and was absent at 90\u00b0F. Pea yield decreased as temperature increased above 60\/50\u00b0F, due mainly to a reduction in the number of pods per plant. The number of peas per pod was decreased by high day\/high night-temperature treatments and by high day temperature treatments imposed prior to full bloom. The combination of high day and high night temperatures caused an increase in the number of nodes to the first flower, whereas number of nodes to the first flower was decreased at the very low temperatures. Percent dry matter of plants was markedly increased at 45\/40\u00b0F.","attrs":{"lang":"en","ns":"http:\/\/purl.org\/dc\/terms\/description","classmap":"dpla:SourceResource","property":"dcterms:description"},"iri":"http:\/\/purl.org\/dc\/terms\/description","explain":"A Dublin Core Terms Property; An account of the resource.; Description may include but is not limited to: an abstract, a table of contents, a graphical representation, or a free-text account of the resource."}],"DigitalResourceOriginalRecord":[{"label":"Digital Resource Original Record","value":"https:\/\/circle.library.ubc.ca\/rest\/handle\/2429\/37122?expand=metadata","attrs":{"lang":"en","ns":"http:\/\/www.europeana.eu\/schemas\/edm\/aggregatedCHO","classmap":"ore:Aggregation","property":"edm:aggregatedCHO"},"iri":"http:\/\/www.europeana.eu\/schemas\/edm\/aggregatedCHO","explain":"A Europeana Data Model Property; The identifier of the source object, e.g. the Mona Lisa itself. This could be a full linked open date URI or an internal identifier"}],"FullText":[{"label":"Full Text","value":"EFFECTS OF TEMPERATURE ON THE GROWTH AND DEVELOPMENT OF PISUM SATIVUM L. CULTIVAR DARK SKIN PERFECTION toy BARRIE STANFIELD B.S.A., The University of B r i t i s h Columbia, 1963 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN AGRICULTURE i n the Divi s i o n of Plant Science We accept t h i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1965 I n p r e s e n t i n g t h i s t h e s i s i n . p a r t i a l f u l f i l m e n t o f t h e r e q u i r e m e n t s f o r an a d v a n c e d d e g r e e a t t h e U n i v e r s i t y o f \u2022 B r i t i s h C o l u m b i a , I a g r e e t h a t t h e L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y * I f u r t h e r a g r e e t h a t p e r -m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by t h e Head- o f my D e p a r t m e n t o r by h i s r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t , c o p y i n g o r p u b l i -c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n * D i v i s i o n fre-paae feme l i b c f Plant Science The U n i v e r s i t y o f B r i t i s h C o l u m b i a , V a n c o u v e r 8, C a n a d a i i ABSTRACT Ef f e c t s of day\/night temperature regimes ranging from 45\/40 to 90\/75\u00b0P on growth- .and development of Dark Skin Perfection peas were studied i n controlled-environment cabinets. Light i n t e n s i t y was about 1500 foot-candles and. the photpp.eriod was 16 hours. Rate of plant development, i n terms .of.nodes produced per day, increased steadily as the average temperature increased. Rate of stem elongation, however, was most rapid at 70\/55\u00b0F; and plant height was greatest at 60\/50\u00b0]?. On a dry matter accumulation per day basis, vine growth decreased above and below a temperature optimum which shifted from 70\/60 to 60\/50\u00b0F i n the course of plant development. T i l l e r i n g was most p r o l i f i c at the lower tempera-tures and was absent at 90\u00b0F. Pea y i e l d decreased as temperature increased above 60\/50\u00b0F, due mainly to a reduction i n the number of pods per plant. The number of peas per pod was decreased by high day\/high night-temperature treatments and by high day temp-erature treatments imposed p r i o r to f u l l bloom. The combination of high day and high night temperatures caused an increase i n the number of nodes to the f i r s t flower, whereas number of nodes to the f i r s t flower was decreased at the very low temperatures. Per-cent dry matter of plants was markedly increased at 45\/40\u00b0F. v i i ACKNOWLEDGEMENT The author i s indebted to Dr. B.P. Ormrod, Di v i s i o n of Plant Science, under whose d i r e c t i o n t h i s research project was conducted, f o r h i s assistance i n the writing and preparation of t h i s thesis. Thanks are also extended to the following members of the thesis committee: Dr. V.C. Brink - D i v i s i o n of Plant Science Dr. C A . Hornby - Di v i s i o n of Plant Science Dr. E.H. Gardner - D i v i s i o n of S o i l Science Dr. H.F. Fletcher - Canada Department of Agriculture This project was supported l a r g e l y by funds supplied by a Canada Department of Agriculture Extra Mural Research grant. F i n a n c i a l assistance was also derived from scholarships provided by the B r i t i s h Columbia Sugar Refining Company Limited and the Vancouver B'nai B ' r i t h H i l l e l Foundation. Credit f o r the photograph of pea node stages i s given to Donald Jaffray, Canada Department of Agriculture. The author i s grateful to his wife f o r her help i n the typing of t h i s t h e s i s . i i i TABLE OF CONTENTS Page INTRODUCTION 1 REVIEW OF LITERATURE 2 MATERIALS AND METHODS 23 RESULTS 32 DISCUSSION 60 SUMMARY 69 LITERATURE CITED 71 i v LIST OF TABLES Table 1. Description of f r a c t i o n a l stages of node deve-lopment . Table 2. Total growth of pea plants grown at 90\/75, 90\/ 60 and 75\/60\u00b0F day\/night temperatures. F i r s t experiment. Table 3. Growth components at maturity harvest of pea plants grown at 90\/75, 90\/60 and 75\/60\u00b0F day\/ night temperatures- F i r s t experiment. Table 4. Total growth of pea plants grown at 90\/75, 90\/ 60\u00b0F day\/night temperatures. Second experi-ment. Table 5. Growth components at maturity harvest of pea plants grown at 90\/75, 90\/60 and 75\/60\u00b0F day\/ night temperatures. Second experiment. Table 6. Total growth of pea plants grown at 85\/70, 85\/ 60 and 70\/60\u00b0F day\/night temperatures. Third experiment. Page 27 33 34 35 36 38 Table 7. Growth components at maturity harvest of pea plants grown at 85\/70, 85\/60 and 70\/60\u00b0F day\/ night temperatures. Third >experiment. Table 8. Total growth of pea plants grown at 70\/60, 70\/ 66 and 70\/50\u00b0F day\/night temperatures. Fourth experiment. Table 9. Growth components at maturity harvest of pea plants grown at 70\/60, 70\/55 and 70\/50\u00b0F day\/ night temperatures. Fourth experiment. Table 10. Total growth of pea plants grown at 90\/60, 85\/ 60, 80\/60, 75\/60, 70\/60 and 70\/50\u00b0F day\/night temperatures. F i f t h experiment. Table 11. Growth components at maturity harvest of pea plants grown at 90\/60, 85\/60, 80\/60, 75\/60, 70\/60 and 70\/50\u00b0F day\/night temperatures. F i f t h experiment. Table 12. Total growth of pea plants grown at 65\/55, 65\/ 50 and 60\/50\u00b0F day\/night temperatures. Sixth experiment. Table 13. Growth components at maturity harvest of pea plants grown at 65\/55, 65\/50 and 60\/50\u00a9F day\/ night temperatures. Sixth experiment. 39 40 41 42 44 45 46 V Table 14. Total growth of pea plants grown at 55\/40 and 45\/40\u00b0F day\/night temperatures. Seventh ex-periment . Table 15. Total growth of pea plants started at 75\/60\u00b0F day\/night temperatures and shifted to 85\/60\u00b0P at the sixth, tenth or f i f t e e n t h node stages. Eighth experiment. Table 16. Growth components at maturity harvest of pea plants started at 75\/60\u00b0P day\/night tempera-tures and shifted to 85\/60\u00b0F at the sixth, tenth or f i f t e e n t h node stages. Eighth ex-periment. Table 17. Total growth of pea plants grown at 75\/60\u00b0F day\/night temperatures and shifted to 85\/60\u00b0F at c e r t a i n growth stages. Ninth experiment. Table 18. Growth components at maturity harvest of pea plants grown at 75\/60\u00b0F day\/night temperatures and shifted to 85\/60\u00b0F at certain growth stages. Ninth experiment. Table 19. Total growth of pea plants started at 70\/60 or 90\/60\u00b0F day\/night temperatures and shifted to 90\/60 or 70\/60\u00b0F at.the thirteenth node. Tenth experiment. Table 20. Growth components at maturity harvest of pea plants started at 70\/60 or 90\/60\u00b0F day\/night temperatures and shifted to 90\/60 or 70\/60\u00b0F at the thirteenth node. Tenth experiment. Table 21. Dry matter accumulation rates of pea plants as influenced by temperature. Grams dry matter\/ day. (Computed from: dry weight at a growth stage divided by number of days from planting to that stage.) Table 22. Node development and stem elongation rates of pea plants from approximately the f i f t h node to f u l l bloom stages as influenced by tempera-ture. Linear regression analysis, where Y= node stage, X=time i n days. Table 23. Intemode lengths of pea plants as influenced by temperature, mm. Page 47 49 50 51 52 54 55 56 57 58 v i LIST OF FIGURES Page Figure 1. Fractional stages of pea node development. 26 Figure 2. The young pea plant showing lo c a t i o n of nodes 28 and internodes. 1 . INTRODUCTION Peas are an important processing crop i n the Lower Mainland of B r i t i s h Columbia. Relatively high y i e l d s are obtained i n t h i s region as a result of generally favourable climatic conditions. However, y i e l d s vary widely between locations and from year to year. Low y i e l d s may be the result of such factors as high tempera-tures, mineral d e f i c i e n c i e s , drought, and insect and disease dam-age, acting singly or i n combination. Peas are well known as a \"cool-season\" crop and i t appears that, of the various environmen-t a l factors which affect pea y i e l d , temperature i s of special importance. Under normal growing conditions i n the f i e l d , the effects of high temperature on plant growth are d i f f i c u l t to separate from the usually accompanying factors of high l i g h t intensity and low s o i l moisture. Furthermore, the response to temperature may be modified by other factors, such as photoperiod and s o i l f e r t i l i t y . The p a r t i c u l a r e ffects of temperature, therefore, can best be determined by studying plant response under controlled-environment conditions. The object of the present experiments, conducted i n controlled-environment cabinets, was to determine the effects of various day\/ night temperature regimes on the growth and development of a pea variety (Dark Skin Perfection) used commercially i n the Lower Main-land region. The primary interest i n these experiments was i n observing the cumulative effect of temperature l e v e l s held con-stant throughout the l i f e of the plant; but some consideration was also given to the effect of changes i n temperature at various growth stages. 2. REVIEW OF LITERATURE The general e f f e c t s of temperature on the growth and devel-opment of peas were summarized as follows by Beattie et a l . , (1942). \"The pea i s a cool-weather plant. Not only w i l l the seeds germinate and make vigorous growth at lower temperature than those of many other vegetable crops, but cool weather i s necessary f o r obtaining good y i e l d s and high quality. High temperature checks the growth of the plants and causes them to flower and form pods before the plants have attained enough size to bear a good crop, while cool weather permits a long-continued growth and the formation of many pods that do not reach the harvest stage prematurely. Besides stunting the growth of vines and reducing the y i e l d , hot weather increases the rate of maturity so greatly that i t i s often impossible to harvest the crop at the proper stage of development, with a conse-quent l o s s i n quality of the product. The young plants w i l l endure some f r o s t without serious damage, but the blossoms and young pods may be k i l l e d by a temperature that would not greatly injure the other parts of the plant.\" The e a r l i e s t studies of temperature e f f e c t s on peas were those of Brenchley (1920). Peas were grown i n the greenhouse through-out the year f o r her experiments. The rate of maturation increased with increasing temperature. During the period of active growth, the shoot increased i n weight f a r more rapidly than the root, and thus, the shoot\/root r a t i o rose steadily. Rise i n temperature did not have the same b e n e f i c i a l effect on root growth as i t did on shoot growth, as no sharp r i s e s i n root weight were observed as temperatures rose, i n contrast to shoot weight which rose with increasing temperature. Cessation of root growth always occurred some time before the shoot stopped growing ( i . e . weight increase). Her data showed that the maximum rate of increase i n weight was attained p r i o r to flowering. The rate f e l l o f f a f t e r reaching the maximum, but an abrupt r i s e i n the rate of growth was observed f o r a period which may have been connected with the 3. i n i t i a t i o n of sexual reproduction. Other early studies of temperature e f f e c t s on peas were the experiments of Boswell (1926). He seeded peas i n Maryland at about weekly inter v a l s from the end of March u n t i l the middle of May. In general, as the date of planting was delayed, the mean temperature to which any given period of development was subjected increased. The higher the temperature, the l e s s was the time re-quired f o r a given period of development. The higher the tempera-ture, the lower was the weight of plant and weight and number of pods per plant. The number of peas per pod was p r a c t i c a l l y un-changed and there was no loss i n weight of peas per pod. Most of the loss i n y i e l d was occasioned through the setting of a smaller number of pods per plant. Under the climatic conditions des-cribed and f o r the factors studied, temperature was the most noticeable factor influencing y i e l d and development of garden peas. In l a t e r work, Boswell (1929) found that the closest inverse relationship between high temperature and y i e l d was f o r the per-iod between blossoming and harvest. Further studies on the effect of temperature on pea develop-ment were not reported u n t i l 1951. Experiments conducted by Fuchs and Muhlendyck (1951) showed that the length of time from germina-t i o n to appearance of the f i r s t flower i n peas depended on the date of sowing. The minimum length of that period, however, was ch a r a c t e r i s t i c of the variety and independent of seasonal weather fluctuations. In addition to daylength, temperature was found to have an important influence on flowering time to the extent that mean temperature sums required were a v a r i e t a l c h a r a c t e r i s t i c . Went (1957) reported on the experimental work with peas conducted at the C a l i f o r n i a Institute of Technology. Germina-t i o n at a high temperature (26\u00b0C) was faster, but the plants were l e s s uniform than when germinated at 23\u00b0 or 20\u00b0C. The optimal rate of stem elongation shifted from higher to lower temperatures i n the course of development. Work with Alaska peas showed that when the maximal d a i l y rates of growth at di f f e r e n t night temperatures were compared, the values varied between 37 and 39 mm.\/day over the range of 7\u00b0 to 20\u00b0C, with 34mm.\/day at 4\u00b0C, and 29 and 27 mm.\/day at 23\u00b0 and 26\u00b0C. Over the ranges of 17\u00b0 to 30\u00b0C day temperatures, the maximal growth rates were 33, 37, 39, 33 and 26 mm.\/day f o r 17\u00b0, 20\u00b0, 23\u00b0, 26\u00b0, and 30\u00b0C. The optimal growth temperature was 20\u00b0 to 23\u00b0C i n t h e i r early growth, 10\u00b0 to 17\u00b0C one month a f t e r germination and even lower a f t e r one and one-half months. F r u i t i n g responded very much l i k e vegeta-t i v e growth to temperature and l i g h t . At a high temperature (23\u00b0C) hardly any seeds were set, and pea weight was low. At the higher temperature only one or a few seeds developed per pod with one or two pods per plant. At the lower, temperatures a l l ovules grew into seeds. Fresh and dry weight of the whole plant was affected by the environment i n a similar way to stem elongation. The curve f o r growth rate of the pea gradually rose f o r the period up to 25 days a f t e r sowing. Under constant growing condi-tions the morphological development, of the pea plant had a con-stant growth rate up to the time of flowering. The growth rate decreased a f t e r the flowers appeared. The morphological develop-ment of the pea plant had a very d i f f e r e n t temperature r e l a t i o n -ship when compared with i t s physiological development. Morpho-5. l o g i c a l development increased steadily with temperature, the day temperature being as eff e c t i v e as the night temperature, and causing an increase of 0.01 nodes per 12 hours per \u00b0C. Highkin (1958) showed that a lack of day\/night temperature flu c t u a t i o n was i n h i b i t o r y f o r growth despite the fact that the constant temperature may be near the opt imal temperature. Lambert and Linck (1958) treated Alaska peas with high tem-peratures during a period from f i v e days before f u l l bloom to 15 days a f t e r f u l l bloom and found reductions i n fresh weight and the number of peas which were of canning s i z e . A l l treatments at high temperatures were not equally e f f e c t i v e i n reducing y i e l d of peas. It was found that exposures to 32\u00b0C (90\u00b0P) reduced y i e l d more than 29\u00b0C (85\u00b0P) and 29\u00b0C more than 27\u00b0C (80\u00b0F). Exposure to high temperature f o r six-hour periods i n the middle of the l i g h t period on f i v e consecutive days reduced y i e l d more than three days and three days more than one day. Plants treated at f i v e days a f t e r f u l l bloom were most severely affected by high temperatures. Plants treated at f i v e days a f t e r f u l l bloom at 27\u00b0, 29\u00b0, or 32\u00b0C and f o r one, three or f i v e days were lower y i e l d i n g than comparable treatments at other stages of develop-ment. Within each of the four stages of development studied, fresh weight of peas was reduced more with increasing temperature from 27\u00b0 to 29\u00b0 to 32\u00b0C and with increasing duration from one to three to f i v e days. Dry matter accumulation and elongation of Unica pea plants growing at two l e v e l s of day\/night temperatures (10\/10, 10\/20, 20\/10, 20\/20\u00b0C) over a period of one month were investigated by Monselise and Went (1958). Treatments began when plants grow-6. ing at 20\/l4\u00b0C had four to f i v e leaves. Elongation was greatest at high day temperatures (20\/20, 20\/10\u00b0C) even i f t h i s meant a lower t o t a l of degree-hours per d a i l y cycle. Dry matter accumula-t i o n was highest at 10\/10\u00b0C, followed by 20\/10 and 20\/20\u00b0C. The lowest was at 10\/20\u00b0C, where l e a f chlorosis was pronounced. Growth of roots (dry weight) was best at 10\/10\u00b00 and, therefore, also top\/root r a t i o was lowest, because of depressed growth of tops and unhampered or even increased translocation to roots. Mention was made of the fact that plants growing at 10\/10\u00b0C began to branch (fourth harvest), while no branching was found at 20\/20\u00b0C. The effect of high temperatures during periods of r e l a t i v e l y short duration (three to four days) at various stages following anthesis at the f i r s t bloom node was studied i n r e l a t i o n to y i e l d of Alaska peas at t h i s node (Karr, et aj.., 1959). The control temperatures were 24\/l5\u00b0C Three temperature treatments were studied: 32\/15, 24\/30 and 32\/30\u00b0C. The data revealed the exis-tence of a r e l a t i v e l y well-defined thermal-sensitive period, with maximal s e n s i t i v i t y to high day temperatures occurring about six to nine days a f t e r f u l l bloom. High night temperatures proved more c r i t i c a l , r e s u l t i n g i n a maximal reduction of 25 percent i n y i e l d , as opposed to about eight percent f o r high day tempera-tures. The effect of high day and night temperatures combined tended to be roughly additive. Many pea processors use a system of accumulated degree-hours, or \"heat u n i t s \" to determine dates of planting of peas and to predict harvest dates (Thompson and Ke l l y , 1957). This concept has been reviewed by Seaton (1955). The basis f o r use of heat units i s presented together with working d e t a i l s and merits and 7. l i m i t a t i o n s of the technique. Holmes and Robertson (1959) also presented a detailed review of the relationship of heat units to crop growth. They noted the importance of the fact that the sum-mation constant f o r any one pea variety w i l l vary with geographic locat i o n . It was not considered feasible to establish a d e f i n i t e value f o r summation constant f o r a variety and expect i t to be usable under a l l conditions. A summation of degree hours above a base temperature of 40\u00b0P correlated c l o s e l y with plant development i n peas (Boswell, 1926). Blossoming occurred upon the reception of a f a i r l y con-stant amount of heat, regardless of time. Heat summation to har-vest was more variable than that to blossoming. The relationship between heat unit accumulation and tendero-meter readings was studied using temperature records f o r Alaska and Sweet peas over a three-year period i n Wisconsin (Katz, 1952). It was found that e s s e n t i a l l y a l i n e a r relationship existed. The heat accumulation necessary to bring the crop to the same stage of maturity as represented by a given tendero-meter value was not constant, but varied i n such a way that i t was lower when the season was cool and higher when the season was warm. Many s c i e n t i s t s have c r i t i c i z e d t h i s heat-unit method on the basis that temperature effects are not uniform throughout the growing season and that temperature i s not the only factor i n f l u -encing growth of the crop. Went (1950) stated that: \" A l l heat sum calculations are based on the false-assumption that there i s a di r e c t propor-t i o n a l i t y between growth and temperature. Actu-a l l y , above a certain optimum temperature, the rate of development decreases with r i s i n g tempera-8. ture. Besides, i t does not take into account that mainly night (or day) temperature controls devel-opment i n certain plants.\" Wang and Bryson (1956) pointed out that the responses of peas to temperature varies with the p l a n t s stage of development. They divided the plant's l i f e cycle into underground, seedling, vegeta-t i v e and reproductive stages; and showed that the optimum tempera-ture range changed from about 57-76\u00b0 to 65-88\u00b0 to 50-70\u00b0P as the plant passed through these four stages. Nuttonson (1948) incorporated the effect of photoperiod into the heat sum to account f o r the flowering and maturity behaviour of Alaska peas. In f i e l d plantings (Reath and Wittwer, 1952), the multiple of degree-days summation and average length of daylight was found to be a le s s variable expression than the heat summation alone. Experiments by Ottoson (1958) indicated that the heat r e -quirement of the pea varies with the l i g h t f actor. Sowing l a t e resulted i n an increased requirement of heat-units. Variation of s o i l type and nutrient supply also influenced the heat-unit r e -quirement f o r maturation. In a c r i t i q u e of the heat-unit approach, Wang (i960) i n d i -cated the need f o r a number of improvements i n the method includ-ing: recording of representative temperatures of the microclimate, change of threshold temperatures according to age of plant, d i f -f e r e n t i a t i o n of growth and development, correction of non-linearity of plant-environment relationships, and combining environmental parameters to give weighted values. Wang (1962) compared y i e l d records f o r the state of Wisconsin fo r the years 1918 to I960 with the seasonal temperature ranges, 9. termed the TD values. The TD value referred to the difference bet-ween the monthly mean temperature f o r the general planting stage ( A p r i l and May) and the monthly mean temperature f o r the general harvesting stage (June and J u l y ) . Wang found that an average of over 75 percent of the y i e l d figures were well correlated with the temperature parameter. Hamson et a l . . (1955) indicated that plantings i n New York made i n A p r i l c l e a r l y yielded more than those made i n May. In a report on studies of the reaction of peas to planting date, van Dobben (1963) indicated that long days and higher temperatures i n l a t e spring lead to a decrease i n plant size and f i n a l y i e l d through a shortening of the growing period which i s not completely compensated f o r by more rapid growth per unit of time. Varie t i e s suitable f o r l a t e sowing should be day-neutral, have a low acceler-ation of phasic development at higher temperatures and a large i n -crease i n growth rate at higher temperatures. Considerable v a r i e -t a l differences were found i n reaction to daylength and to tempera-ture. Day n e u t r a l i t y was prevalent i n early v a r i e t i e s . Experiments by Proctor (1963) i n B r i t a i n indicated that there i s a clear y i e l d trend i n favour of early sowing. He also cited evidence of greater branching of e a r l i e r sown plants. ....... Early experiments on temperature effects on root growth were conducted by Leitch (1916). She measured growth of the roots i n length. The r e l a t i o n of growth to temperature could be expressed as a uniform curve from -2\u00b0 to about 29\u00b0C. Minus 2\u00b0C was the low-est temperature at which growth took place (minimum); 45\u00b0C was the maximum (above t h i s temperature growth ceased p r a c t i c a l l y instan-taneously); 29\u00b0C was the optimum temperature: and 30.3\u00b0C was the 10. maximum rate temperature. About 29\u00b0C any increase i n the tempera-ture meant the introduction of a time factor and a consequent con-tinuous decrease i n the growth-rate. Another early reference to work on root temperature effects was that of Brenchley and Singh (1922). Provided i n s o l a t i o n was not excessive, the amount of d a i l y f l u c t u a t i o n of root temperature oyer a range of about 22\u00b0C.(6.7 - 28.9\u00b0C) .had comparatively l i t t l e influence upon growth; high maxima and low minima gave similar re-sults to low maxima and r e l a t i v e l y high minima provided the average mean temperatures were not too d i s s i m i l a r . Brouwer (1959) found that a high root zone temperature of 24\u00b0C was most b e n e f i c i a l at the e a r l i e s t growing stage, while at a l a t e r stage a lower root zone temperature of 17\u00b0C was more favour-able. S t i l l l a t e r a root zone temperature of 10\u00b0C resulted i n the highest dry matter y i e l d s . Brouwer and van V l i e t (i960) grew peas at various root tem-peratures and showed that the greatest increase i n fresh and dry weights of stems, leaves and roots occurred at 22\u00b0C. This tempera-ture was also optimal f o r uptake of water, potassium and n i t r a t e . Potassium uptake i n r e l a t i o n to fresh weight increase was lower at higher temperatures. The transpiration c o e f f i c i e n t increased with the root temperature. In another report, Brouwer (1962) indicated that the growth of peas reached i t s optimum at 15\u00b0C s o i l temperature but peas also grew well at 10\u00b0G s o i l temperatures. The a i r temperature i n these experiments was 20\u00b0C. Growth of peas was shown to be limited by potassium uptake at temperatures above 15\u00b0C and by water d e f i c i -ency below 1 5 G C 11. Lockhart and Gottscba.ll (1961) grew Alaska pea plants with t h e i r a e r i a l portions at either 30\/24 or 17\/ll\u00b0C day\/night tempera-tures, while the roots were maintained at either 30 or 17\u00b0C with-out day\/night fluctuations. Flowers were removed regularly from a l l plants. The rate and extent of stem elongation were deter-mined almost e n t i r e l y by the temperature of a e r i a l portions of the plant. Root temperatures had a much greater influence on dry weights of shoot and roots than on stem elongation. In greenhouse experiments, Klacan (1962) found that the t o t a l number of peas per plant was highest when the root tempera-ture was equal to greenhouse temperature (62-74\u00b0F). High root tem-peratures (80-90\u00b0F) reduced pod f i l l but did not aff e c t pod number or depress nutrient uptake? low root temperatures (39-47\u00b0F) r e -duced nutrient uptake. Dry weights of peas were usually highest at s o i l tempera-tures of 62 and 70\u00b0F and decreases were obtained at 78 GF i n the experiments of Mack, et a l . (1964). However, ef f e c t s of s o i l tem-peratures (54, 62, 70, 78\u00b0F) on dry weights of peas were not great. In general, increases i n dry weights of peas with application of phosphorus were sim i l a r at the four s o i l temperatures. Stalder (1952) studied nodulation of pea roots and found that reduced attacks by the nodule organism were noticeable at about 27\u00b0C Temperatures as low as 6.5\u00b0C did not aff e c t i n f e c -t i o n . The optimum temperatures f o r the growth of the nodule or-ganism, of the host, and of the nodules was about 20 to 24\u00b0C. In studies with Subterranean clover, Possingham, et a l . (1964) found that constant high root temperature (30\u00b0C) s i g n i f i -cantly increased the number of nodules per plant but reduced both 12. the protein and t o t a l nitrogen content of plants not supplied with f e r t i l i z e r nitrogen. By contrast, a constant high shoot tempera-ture (30\u00b0C) had no i n h i b i t o r y effect on nitrogen f i x a t i o n a l -though plant y i e l d was s i g n i f i c a n t l y reduced. Peas and beans grown i n sand culture at a constant a i r tem-perature of 20\u00b0C absorbed s l i g h t l y more nitrogen and mardedly le s s phosphorus when the temperature of the substrate was increased to 32\u00b0C than when i t was maintained at 20\u00b0C. (Gukova, 1961). In sand culture experiments with peas, beans and other l e -gumes, Gukova (1962) found that, whereas the uptake of inorganic nitrogen by.,uninoculated plants increased with a r i s e i n the temper-ature of the medium, i n inoculated plants th e . f i x a t i o n of prganic nitrogen and the growth of the plants were depressed when the tem-perature of the medium exceeded 24-30\u00b0C. Early experiments on temperature requirements f o r germina-t i o n (Kotowski, 1926) indicated that the speed of germination of peas increased as the temperature was increased from 4 to 25\u00b0C, but was no f a s t e r at 30\u00b0C than at 25\u00b0C. Higher Q10 values were obtained at lower temperatures. Peas would tolerate exposure to temperatures as low as 40\u00b0P f o r considerable periods of time, pro-viding steps were taken to protect the seed against pathogenic or-ganisms. Experiments by Dubetz, et a l . (1962) indicated that the per-centage of emergence of peas was not s i g n i f i c a n t l y affected by s o i l temperature, but the v e l o c i t y of emergence increased as s o i l temperature was increased. Fernandes (1923) studied the effect of temperature changes on respiratory a c t i v i t y of four-day-old pea seedlings. The tern-13. perature was changed from an i n i t i a l 25\u00b0C to various other temper-atures. The operation of a time factor was shown by r a i s i n g the temperature to 35\u00b0C, which resulted i n a f a l l i n g - o f f i n r e s p i r a -t i o n rate with time. Increase i n temperature between 0 and 45\u00b0C resulted i n an increase i n the i n i t i a l rate of re s p i r a t i o n , but the rate of f a l l i n g - o f f with time of the r e s p i r a t i o n rate i n -creased as temperature increased above 30\u00b0C. At 30\u00b00 there was no f a l l i n g - o f f i n r e s p i r a t i o n rate with time. Geronimo and Beevers (1964) found that the only effect of exposure to growing temperatures above and below the optimum was that of either accelerating or decelerating the demise of the metabolic system which occurs,.normally with increasing age at the optimal temperature f o r growth. The important factor determining decreased respiratory a c t i v i t y was apparently the degree of matur-i t y ; high growing temperatures accelerated maturation, low tem-peratures decelerated i t . Working with Wisconsin Perfection peas, Waraoek and Hagedorn (1954) showed that at 16\u00b0C the stigmas remained receptive to pollen f o r three days a f t e r emasculation; whereas at 20 and 24\u00b0C the stigmas retained good r e c e p t i v i t y f o r only one day. The re-s u l t s of f i e l d experiments on three pea v a r i e t i e s also pointed to temperature as a factor a f f e c t i n g duration of r e c e p t i v i t y . Studies by Inoue and Suzuki (1955) showed that pollen germ-ination and pollen tube elongation were not s i g n i f i c a n t l y a f -fected by temperatures between 10 and 30\u00b0C, though germination was much reduced at 0 and 40\u00b0C. Masabayashi (1952) reported that the optimum temperature f o r pollen tube growth i n garden peas was 25\u00b00; pollen germination 14. was retarded at 1G\u00b0C and very weak at 0\u00b0C. Linck (1961) found that about one-third of the embryos of Alaska peas f a i l e d to develop under several environmental condi-tions. This embryo f a i l u r e was most frequent i n the end p o s i -tions of the ovules i n the pod. Under the conditions of growth reported i n t h i s paper about 30 tqr 50 percent of the ovules i n a pod (at the f i r s t bloom node) developed to maturity. The tenta-t i v e conclusion was reached from the anatomical study that lack of f e r t i l i z a t i o n was not a cause of the embryo f a i l u r e . Several experiments nave been conducted on v e r n a l i z a t i o n of peas. A plant i n which flowering behaviour i s influenced by cold treatment applied i n the seedling stage i s said to be v e r o a l i z -able. McKee (1935) nas shown that a cold treatment during germ-ination w i l l hasten flowering i n f i e l d peas. Despite t h i s e v i -dence, peas were not generally recognized as being naturally vernalizable. Leopold and Guernsey (1953) reported an in t e r a c t i o n of auxin and temperature i n f l o r a l i n i t i a t i o n of Alaska peas. It was shown that auxin seed treatment followed by 20\u00b0C produced quan-t i t a t i v e i n h i b i t i o n s of flowering. These workers l a t e r reported that application of auxin com-bined with a short cold treatment was e f f e c t i v e i n decreasing the number of nodes to the f i r s t flower (Leopold and Guernsey, 1 9 5 4 ) . The v e r n a l i z a t i o n effect could be n u l l i f i e d , however, by a high temperature treatment (39\u00b00 f o r 18 to 24 hours) applied a f t e r the v e r n a l i z a t i o n treatment. Highkin (1956) worked with Unica and Zelka pea v a r i e t i e s and showed that peas can be vernalized and that the inductive 15. effect of c o l d treatment could be reversed by high temperature (30\u00b0C f o r ten days) treatment, that i s , they could be deverna-l i z e d . Pretreatment during germination at 20 or 26\u00b0C f o r up to f i v e days p r i o r to the optimal cold treatment ( 4 or 7\u00b0C f o r 25 to 30 days) resulted i n a progressive loss of a b i l i t y to be verna-l i z e d . Plants remained vernalizable f o r up to three days at 20\u00b0C. At 26 GC they remained vernalizable f o r only one or two days. The pretreatment at either temperature had no effect on vernalization with respect to vegetative development. In Unica, f u l l v e r naliza-t i o n lowered the f i r s t flowering node from the eighteenth to the fourteenth node. Further work on the effect of a cold treatment on the res-ponse of pea plants to high temperature (26\u00b0C) was carried out by Highkin (1959). He found a marked increase i n heat resistance as a r e s u l t of the cold treatment (germinated at 4\u00b0C f o r 25 days). The induction of heat resistance as a res u l t of verna l i z a t i o n appeared to be independent of the induction of the f l o r a l stimu-lu s r e s u l t i n g from such a treatment. This was indicated by the fac t that v e r n a l i z a t i o n did have an effect i n decreasing heat damage as well as a f f e c t i n g seed v i a b i l i t y i n a s t r a i n of peas which was non-vernalizable so f a r as flowering was concerned. In a s t r a i n which was vernalizable, high temperature caused dever-n a l i z a t i o n with respect to flowering. However, vernalization markedly increased the heat resistance of t h i s s t r a i n . The g r a f t i n g of genetically early scions of Massey peas on genetically l a t e stocks (variety Telephone) l e d to flowering at a higher node (Paton and Barber, 1955). In rec i p r o c a l grafts, the scions of the l a t e v a r i e t y flowered at an e a r l i e r (lower) 16. node. These re s u l t s were explained on the assumption that the genetically l a t e r variety produces a flower i n h i b i t i n g (or delay-ing) substance which can pass a graft union and a l t e r the flower-ing behaviour of genetically early scions. Barber (1959) concluded that the production of an i n h i b i t o r was responsible f o r the a b i l i t y of late v a r i e t i e s to respond to phot\u00a9period and vernalization, the i n h i b i t o r being s e l e c t i v e l y destroyed during long days and at low temperatures. The Dwarf Telephone variety of peas was vernalizable i n the studies of Moore and Bonde (1962). F u l l y imbibed seeds subjected to seven or more days of cold treatment at 4\u00b0 to 7\u00b0C were induced to a t t a i n l e s s height to the f i r s t flowering node, flower at a lower node, and flower i n fewer days as compared to control plants grown i n the greenhouse. Maximum eff e c t s were obtained with about 28 days of cold treatment. The in t e r n a l chemical con-t r o l of flowering i n the Dwarf Telephone pea was ten t a t i v e l y i n -terpreted as being mediated by a flower-promoting hormone, the formation of which was influenced quantitatively by temperature and photoperiod, and the action of which was antagonized by high l e v e l s of endogenous auxin. Al'tergot (1963) characterized the metabolic responses of peas to increased temperature as follows: \"Early effects included i n h i b i t i o n of photo-synthesis and anabolic processes, r e s u l t i n g i n retarded growth and caryolysis i n the meristem-a t i c tissues. The a c t i v i t y of the oxidizing enzymes was increased to a maximum at about 40 C, and re a d i l y oxidizable compounds such as ascorbic acid, glutathione and tannins were destroyed. Young plants were found to adapt themselves to gradually increasing temperatures by the depoly-merization of complex organic compounds, the production of highly hygrophilic substances, the i n t e n s i f i c a t i o n of photosynthetic a c t i v i t y , the 1 7 . production of compounds able to neutralize toxic ammonium derivatives, the formation of heat re-sistant embryonic tissues and the rejuvenation of t h e i r organs by the re-synthesis of decompo-s i t i o n products. F i n a l l y , r t r i s suggested that the resistance of cultivated plants to high tem-peratures can be increased by c u l t u r a l methods which provide optimum growing conditions.\" Bonner (1957) proposed the concept of the \"chemical cure of clim a t i c l e s i o n s , \" which suggested that shortages of ess e n t i a l metabolites r e s u l t i n g from adverse climatic conditions could be overcome by supplying the necessary substances from an external source. It had been shown by Galston and Hand (1949) that the heat i n a c t i v a t i o n of the growth of etiolated pea epieotyle sec-tions could be l a r g e l y prevented by the addition to the medium of small quantities of adenine or related compounds. Alaska pea plants were grown at constant day temperatures of 23\u00b0C and d i f f e r e n t night temperatures: 2, 6, 10, 13, 17, 20, 23, 26 and 30\u00b0C (Galston, 1957). At each temperature the plants were sprayed with 1, 10 or 100 mg\/l adenine sulfate and compared to plants sprayed with water. The r e s u l t s showed that the plants made optimal growth i n stem length at a night temperature of 17\u00b00, growth being inh i b i t e d about 35 percent by a 10\u00b0C deviation i n temperature, either upward or downward. Although adenine was without effect i n the region of the optimum, i t appeared to pro-mote stem elongation s l i g h t l y , both at the higher and the lower temperatures. With regard to stem weight, a somewhat sim i l a r s i t u a t i o n prevailed, except that there appeared to be a somewhat broader temperature optimum extending from about 10 to 17\u00b0C Data on fresh weight of roots showed a very broad temperature optimum f o r growth centered about the surprisingly low value of 10\u00b0C and there was no marked effect of adenine. The most s t r i k -18. ing e f f e c t s of the adenine sprays were noted on leaves, both t h e i r size and weight being enhanced at a l l concentrations and under a l l temperature conditions. As with roots, there was an amazingly broad temperature optimum f o r growth, no large effect being produced by temperature v a r i a t i o n between 10 and 23\u00b0C. With stems, on the other hand, a deviation of only three degrees from the optimum at 17\u00b0C produced greatly depressed elongation. Highkin (1957) found that the amount of adenine i n a heat susceptible variety remained the same at low (14\u00b00) and at high (26\u00b0G) temperatures. In a resistant variety, however, there was at least a 100 percent increase i n the adenine content at 26\u00b0C as compared to t h i s same vari e t y grown at 14\u00b0C. Lockhart (1958) reported that i n h i b i t i o n of stem growth of Alaska peas by high temperatures was not prevented by gibberel-l i c acid treatment. Ketellapper and Bonner (1961) found that regular spray a p p l i -cations of 10 percent sucrose solution to pea plants grown i n a r t i f i c i a l l i g h t at 23\/l7\u00b0C day\/night temperatures caused a 56 percent increase i n dry weight, which made the dry weight equal to that of plants grown under optimal conditions of 17\/l7\u00b0C. Later, Ketellapper (1963) reported that at 30\/23\u00b0C where Progress No. 9 peas would eventually die, spray applications of vitamin C caused an increase i n dry weight; and although the cure was not complete, vitamin C washable to s p e c i f i c a l l y pre-vent part of the temperature injury. A series of experiments with TJnica peas showed that the optimal temperature during the l i g h t period was 17\u00b0C under the conditions used ( l i g h t intensity 900 foot-candles, photoperiod 16 hours, night temperature 17\u00b0C); 19. and a growth reduction resulted when the plants were grown at a day temperature of 23\u00b0C. The reduction could be prevented com-pl e t e l y by spraying plants with a 10 percent sucrose solution. At 26\u00b0C, sucrose could not completely prevent the growth reduc-t i o n . It was found that the rate of photosynthesis was greatly reduced i n plants grown at 23\u00b0C f o r about ten days. Experiments with Unica seeds produced at 20\/l4\u00b0C gave di f f e r e n t r e s u l t s from the above. The optimal day temperature was 23\u00b0C, and sucrose did not prevent the temperature injury. Instead, the growth reduc-t i o n caused by high temperature could be p a r t i a l l y prevented by a vitamin B mixture or by a mixture of ribosides. In a l l these ex-periments the active substances did not promote growth at the op-timal temperature. The growth and ripening processes i n pea seeds were charac-terized by Boswell (1924). He found: a rapid decrease of suc-rose, t o t a l soluble nitrogen, amides, basie nitrogenous substan-ces, amino acids and materials which form humin compounds upon hydrolysis; an increase i n starch, hydrolyzable polysaccharides and insoluble nitrogen; a les s rapid decrease i n t o t a l nitrogen. In a l a t e r report Boswell .(1928) indicated that the low quality product often secured from late-maturing plantings was probably the result of such a rapid rate of maturity under high temperature conditions that the crop could not be (or was not) harvested at the stage at which i t should have been. Even though l a t e planting appeared to have no very harmful effect upon quality, Boswell pointed out that i t should be borne i n mind that l a t e planting materially reduces y i e l d i n most seasons. Stages of maturity were characterized by d i s t i n c t and marked 2G. differences i n composition (Jodidi and Boswell, 1934). In gen-e r a l , more mature peas, i . e . , larger peas, had a larger percent-age of ash, of ether extract ( f a t ) , t o t a l nitrogen, protein n i t r o -gen, starch and a lower percentage of sucrose. On a d r y weight basis the percentages of a l l constituents except starch and pro-t e i n nitrogen decreased as maturity progressed. Differences i n vitamin content of peas r e s u l t i n g from tem-perature differences were studied by Gustafson (1950). Alaska peas were grown at 27 to 30\u00b0C and 10 to 15\u00b0C. Riboflavin was found to be more abundant i n plants grown at the low temperature. Thiamin content was s l i g h t l y higher at the high temperature. Niacin appeared to \u201ebe favoured by the low temperature. Other environmental conditions being si m i l a r , an increase i n the day temperature from 18, 19 or 21\u00b0C to either 25 or 27\u00b0C, generally decreased the nitrogen percentage and the t o t a l n i t r o -gen content of plants (Mes, 1959). An increase i n the night tem-perature from 10 to 21\u00b0C generally also decreased t o t a l nitrogen content although nitrogen percentage often increased. The previous experimental conditions affected not only growth and rate of development of a pea plant but also resulted i n differences i n chemical constituents i n i t s seeds (Highkin, I960). It was found that there was a difference i n the t o t a l amount of protein nitrogen of seeds from two di f f e r e n t environ-mental parental sources when these seeds were grown i n a common environment. At low temperatures, the conversion of sugar to starch was much delayed and sugar continued to increase i n concentration dur-ing growth; at higher temperatures the sugar entering the seeds 21. was rapidly converted to starch (Robertson et a l . , 1962). Pro-t e i n synthesis was also delayed at lower temperatures. Thus the carbohydrate composition of seeds grown at dif f e r e n t temperatures was markedly d i f f e r e n t . The relationship of temperature to photoperiod was studied by Kopetz (1943), who noted that whereas under short-day condi-tions the temperature influence was d e f i n i t e l y masked by the checking effect of the daylength factor, temperature alone deter-mined the development with sowings under long-day conditions. Pea v a r i e t i e s were grown i n the greenhouse at 9-, 12-, and 16-hour photoperiods each at 50 and 60\u00b0P night temperatures, with day temperatures about 10\u00b0C higher, by Reath and Wittwer (1952). At 60\u00b0P, Alaska and Surprise were day-neutral with respect to flowering and pod production, but at 50\u00b0P flowering was hastened by long days. Other v a r i e t i e s behaved as long day plants at both 50 and 60\u00b0P. In a l l midseason and l a t e v a r i e t i e s the number of degree-days required f o r flowering was reduced progressively by exposure to 12- and 16-hour photoperiods. The temperature conditions during vegetative growth modified the photoperiodic response i n the experiments of Paton (1957). In the absence of temperature v a r i a t i o n during the dark period, plants grown i n 8-hour photoperiods flowered 25 to 60 days l a t e r than plants grown i n 16-hour photoperiods. A temperature change of 10 to 19\u00b0G during the dark period almost eliminated the photo-periodic response; 8-hour photoperiod plants i n i t i a t e d the f i r s t flower only six to ten days l a t e r than 16-hour photoperiod plants. The greater the difference between the two temperatures given during the night i n two 8-hour periods, the more flower 22. i n i t i a t i o n was accelerated. Seedlings of early-, medium-, and late-flowering v a r i e t i e s were given long- and short-day treatments as soon as the f i r s t ; leaves had expanded (Nakamura et a l . , 1962). Under short-day ^ (8-hour) treatment, internode elongation of the main shoot and branches was i n h i b i t e d , but the t o t a l number of branches per plant, p a r t i c u l a r l y secondary branches, increased. Late-flowering v a r i e -t i e s responded to photoperiodic treatment more than early-flowering v a r i e t i e s , except when they were grown during a warm season. Short-day treatment increased branching from basal nodes and long-day treatment increased branching from higher nodes., Vernalization of seeds at i-3\u00b0C f o r 20 or 30 days also increased the number of branches from high nodes. The number of nodes to the f i r s t flower on the main shoot decreased with long-day treatment or seed vern-a l i z a t i o n . This response was most marked i n l a t e v a r i e t i e s . 23. MATERIALS AND METHODS Experiments were conducted i n controlled-environment cabin-ets (Ormrod, 1962), equipped with 80 percent cool white and 20 percent Gro-Lux fluorescent l i g h t s , which provided a l i g h t inten-s i t y of about 1500 foot-candles at plant l e v e l (measured with a Weston Model 756 illumination meter without cosine f i l t e r ) . From two to six cabinets were used at one time. The photoperiod was 16 hours of l i g h t i n each 24-hour cycle. A supply of pea seed, c u l t i v a r Dark Skin Perfection, was ob-tained i n the summer of 1963 from the Agassiz Experimental Farm and used f o r a l l experiments described here. Dark Skin Perfection i s a l a t e freezing variety, recommended fo r commercial growing i n the Lower Mainland of B r i t i s h Columbia. Seeds were treated with Nitragin ( , C culture) legume inocu-lant and planted i n one-gallon, green p l a s t i c pots f i t t e d with drain holes and f i l l e d with an autoclaved, f e r t i l e greenhouse s o i l mixture. The s o i l was s l i g h t l y acid (pH=6.5), with an open struc-ture and high organic matter content. The s o i l surface was covered with a one-half inch layer of peat moss to reduce evapora-t i o n . The pots were placed i n aluminum pans and randomly assigned to the growth cabinets, eight pots per cabinet. Plants were watered regularly by surface i r r i g a t i o n , except i n Experiment 1, i n which sub - i r r i g a t i o n was used. Seedlings were thinned to four uniform plants per pot when plants had reached the t h i r d node stage. Plants were supported by means of wire screens f i t t e d oyer the rims of the pots. Development of the pea plant, i n terms of number of v i s i b l e nodes was observed from the f i f t h to f i f t e e n t h nodes by recording 24. on each observation day the f r a c t i o n a l stage of development of the unfolding l e a f at the growing point. For each node, ten approxi-mately equal stages were defined and observations were made to the nearest tenth of a node (Figure 1 and Table l ) . This record-ing system was sim i l a r to that designed by Higgins (1952) and modified by Went (1957). One representative plant per pot was chosen f o r detailed ob-servation and a l l observations were averaged f o r a given date. The time between observations varied from one to four days. Ob-servations were made i n the afternoon of each recording date. Three harvests were made during the vegetative period of the plants' development. Plants were harvested when s i x to seven nodes had developed (sixth node stage), when ten to eleven nodes had developed (tenth node stage), and when the majority of plants had developed f u l l y reflexed flowers ( f u l l bloom stage). Two pots of plants were harvested at each growth stage. Green and dry weights of vines, cut of f at node sub-1 (Figure 2), were determined. Drying was accomplished by placing the fresh plant material i n a forced draft oven at 50\u00b0C f o r 48 hours. A maturity harvest was made when peas were v i s u a l l y judged to have reached optimum canning maturity. Measurements at t h i s harvest included green and dry weights of vines, pods, and peas, numbers of pods per plant, peas per pod, pos i t i o n of f i r s t flower, internode lengths, and occurrence of t i l l e r i n g . Only those peas with a diameter larger than 9\/32 inch were included i n measure-ments of peas per pod and pea weights. Ten separate experiments were conducted. In seven experi-ments plants were grown under a pre-set f l u c t u a t i n g day\/night 25. Figure 1. Fractional stages of pea node development. 27 Table 1. Description of f r a c t i o n a l stages of node development. Node Stage Description 0.1 Stipules enclose a l l but the very t i p of the next p a i r of l e a f l e t s . 0.2 Leaflets v i s i b l e above the stipules by approximately one-quarter inch. 0.3 Leaflets further emerged but s t i l l p a a r t i a l l y enclosed by the s t i p u l e s . 0.4 Leaflets have now emerged clear of the s t i p u l e s , which are s t i l l closed. The emerged l e a f l e t s are s t i l l c losely associated and have not opened. 0.5 New l e a f l e t s are f u l l y exposed; the second p a i r of l e a f -l e t s are f o l d i n g back and show a s l i g h t tendency towards r e f l e x i o n to form a \"V\". 0.6 Leaflets form a well defined \"V\", edges of the l e a f l e t s are s t i l l closed, although some l e a f expansion i s evident. 0.7 Leaflets beginning to open along t h e i r edges. The grow-ing t i p of the next set of l e a f l e t s i s v i s i b l e i f the stipules are pulled back, but i s very small (less than h a l f the length of the s t i p u l e s ) . 0.8 The t i p of the next set of l e a f l e t s i s s t i l l enclosed i n the s t i p u l e s , but i s now approximately two-thirds of the length of the stipules ( i n the photograph the stipules are folded open). 0.9 The next set of l e a f l e t s i s s t i l l enclosed by the s t i p -ules, but i s very close to being v i s i b l e . (Stipules are folded back i n the photograph). 1.0 The t i p of the next set of l e a f l e t s i s just v i s i b l e above the s t i p u l e s . Stipules beginning to open along t h e i r margins. 28. Figure 2. The young pea plant showing location of nodes and internodes. 29. temperature regime from seeding to maturity and four harvests were made as described above. Some of the temperature treatments were repeated i n order to determine the repe a t a b i l i t y of tempera-ture e f f e c t s i n di f f e r e n t experiments. Three experiments i n -volved changing the day temperature at various stages of the plants' development. In these experiments the y i e l d at the matu-r i t y harvest was of chief concern. Experiment 1 Plants were grown from seeding to maturity at day\/night tem-peratures of 90\/75, 90\/6G and 75\/60\u00b0F. Experiment 2 This experiment was a r e p e t i t i o n of the f i r s t experiment. Experiment 3 Plants were grown from seeding to maturity at 85\/70, 85\/60 and 70\/60. Experiment 4 Plants were grown from seeding to maturity at 70\/55 and 70\/50. Plants were also grown at 70\/60 and harvested at the sixt h node, tenth node and f u l l bloom stages to provide a check of r e s u l t s obtained i n the t h i r d experiment. Experiment 5 Plants were grown from seeding to maturity at 90\/60, 85\/60, 80\/60, 75\/60, 70\/60 and 70\/50. This experiment was es s e n t i a l l y a r e p e t i t i o n of previous experiments, except f o r the inclusions of the 80\/60 treatment. Experiment 6 Plants were grown from seeding to maturity at 65\/55, 65\/50 and 60\/50. 30. Experiment 7 Plants were grown from seeding to maturity at 55\/40 and 45\/40 i n two Pereival controlled-environment cabinets, using the same l i g h t source as f o r the other experiments, adjusted to ap-proximately the same l i g h t i n t e n s i t y . Plants were harvested at the s i x t h node, tenth node and f u l l bloom stages. Experiment 8 Plants were grown at 75\/60 from seeding to a given growth stage. The day temperature was then raised to 85 and the plants grown at 85\/60 u n t i l maturity. The s h i f t i n day temperature was made at either the s i x t h node, tenth node or f u l l bloom stage. Harvests were made at the tenth node, f u l l bloom and maturity stages. Plants were also grown continuously at 75\/60 and har-vested at the s i x t h node, tenth node and f u l l bloom stages. Experiment 9 Plants were subjected to a high temperature treatment of 85\/60 during the period from seeding to s i x t h node, from s i x t h to tenth nodes, from tenth to f i f t e e n t h nodes or from f i f t e e n t h node to plus ten days; otherwise, the plants were grown at 75\/60. Plants were harvested at maturity. Experiment 10 Plants were subjected to a high temperature treatment of 90\/60 during the period from seeding to thirteenth node or from thirteenth node to maturity; otherwise, the plants were grown at 70\/60. Plants were harvested at maturity. Data obtained i n a l l experiments was s t a t i s t i c a l l y evaluated using analysis of variance methods followed by L.S.D. or Duncan's multiple range t e s t s , or, i n certai n cases, using regression anal-3 1 . yses. Most of the s t a t i s t i c a l analyses were carried out using the IBM 7040 computer (U.B.C. Computing Center). In the presentation of r e s u l t s and i n discussion only those differences which were s i g n i f i c a n t at the 5$ l e v e l were consid-ered to he meaningful and worthy of comment. The 5$ l e v e l was selected because of i t s wide use as a significance l e v e l i n plant research. 32. RESULTS In the f i r s t experiment, green and dry weights of pea plants were consistently higher at the 75\/60\u00b0F day\/night temperature than at 90\/75 or 90\/60\u00b0F (Table 2). The number of days to maturity and plant height were l e s s at 90\/60\u00b0P than at 90\/75 or 75\/60\u00b0P. Percent dry matter was unaffected by temperature but was higher at the maturity growth stage than at other growth stages. Pea and pod y i e l d s at maturity harvest were depressed a t 90\/75 and 90\/60\u00b0P compared to 75\/60\u00b0F (Table 3). Differences i n vine growth and t i l l e r i n g were not demonstrated. There was a re-duction i n number of pods per plant from 75\/60 to 90\/75 to 90\/60\u00b0P. There were also more pod pairs at 75\/60\u00b0F than at the other temper-atures. The f i r s t flowering node was markedly higher a t the 90\/75\u00b0P temperature. The r e s u l t s of the second experiment were similar to those of the f i r s t . Differences among temperatures were similar at a l l growth stages (Table 4). The only difference from the f i r s t ex-periment was i n the effect of temperature on percent dry matter at the tenth node stage f o r which 75\/60\u00b0F plants were lower than 90\/75 or 90\/60\u00b0F plants. Differences among temperatures i n pea dry weight were not demonstrated i n the second experiment but differences i n vine green and dry weight were demonstrated (Table 5). There was more vine and more t i l l e r i n g at 75\/60\u00b0F than at the other temperatures. Trends i n temperature effects on pods per plant, peas per pod, and pod pairs per plant were si m i l a r to those i n the f i r s t experi-ment but there were some differences i n significance. Other temperature ef f e c t s were similar with the same significance as 33. Table 2. Total growth of pea plants grown at 90\/75, 90\/60 and 75\/60\u00b0P day\/night temperatures. F i r s t experiment. Growth Stage Temp. Op Days to Growth Stage Green Weight gm\/nlant Dry Weight gm\/nlant Dry Matter Percent Sixth 90\/75 19 2.08 b* 0.25 b 11.97 a node 90\/60 19 1.97 b 0.23 b 11.56 a 75\/60 19 3.57 a 0.40 a 11.01 a Tenth 90\/75 26 4.38 b 0.44 b 10.21 a node 90\/60 26 4.67 b 0.47 b 10.02 a 75\/60 26 9.15 a 0.85 a 9.42 a F u l l 90\/75 43 15.74 ab 1.94 a 12.17 a bloom 90\/60 42 13.48 b 1.71 a 12.99 a 75\/60 42 21.53 a 2.64 a 12.50 a Maturity 90\/57 63 26.19 b 4.98 b 19.01 a 90\/60 53 16.36 b 2.96 b 18.09 a 75\/60 66 51.68 a 9.30 a 18.00 a Plant Height Inches 29.2 a 19.5 b 30.2 a * Means followed by the same l e t t e r are not s i g n i f i c a n t l y d i f f e r e n t at the 5% l e v e l (Duncan's multiple range t e s t ) . Comparisons within growth stages only. 34. Table 3. Growth components at maturity harvest of pea plants grown at 90\/75, 90\/60 and 75\/60\u00b0F day\/night tempera-tures. F i r s t experiment. 1 Peas Pods Vine Temp. \u00b0F Green gm\/ plant Dry m\/ plant Dry Matter Percent Green gm\/ plant Dry gm\/ plant Green gm\/ plant Dry ml plant 90\/75 90\/60 75\/60 4.96b 3.38b 11.90a 1.40b 0.78b 2.72a 28.23a 22.08a 22.86a 5.09b 3.55b 14.38a 0.75b 0.52b 2.13a 16.14a 9.43a 25.40a 2.83a 1.66a 4.45a Temp, pp Pods\/ Plant Number* Peas\/ Pod Number Pod F i r s t Pairs\/Plant Flowering Number* * Node Plants with T i l l e r s Proportion 90\/75 90\/60 75\/60 3.9 b 2.0 c 6.9 a 2.7 b 4.1 a 3.9 ab 0.3 b 0.0 b 1.8 a 20.0 b 16.0 a 15.6 a 0 a 0 a 3\/8 a * Only those pods which contained peas of the required size were counted. ** Number of nodes at which two pods developed. 35. Table 4. Total growth of pea plants grown at 90\/75, 90\/60\u00b0P day\/night temperatures. Second experiment. 'Growth 'Stage 'Temp. , O p * Days to Growth 'Stage 'Green Weight gm\/plant Dry Weight gm\/nlant (Dry Matter Percent Plant Height 1 Inches Sixth 90\/75 16 1.70 b ,0.18 b ,10.48 a node 90\/60 17 2.03 b 0.21 b 10.15 a 75\/60 19 3.90 a 0.37 a 9.55 a Tenth 90\/75 23 4.25 b 0.45 b 10.65 b node 90\/60 24 4.81 b 0.50 b 10.32 b 75\/60 27 11.60 a 1.07 a 9.22 a F u l l 90\/75 41 14.59 b 1.58 b 11.92 a bloom 90\/60 38 13.20 b 1.70 b 11.52 a 75\/60 41 31.30 a 3.41 a 10.82 a Maturity 90\/75 60 32.47 b 5.67 b 17.46 a 27.9 ab 90\/60 54 28.47 b 4.62 b 16.23 a 23.0 b 75\/60 63 69.16 a 10.97 a 15.86 a 34.8 a 36 Table 5. Growth components at maturity harvest of pea plants grown at 90\/75, 90\/60 and 75\/60\u00b0F day\/night tempera tures. Second experiment. Peas Pods Tgmp. Green gm\/ plant Dry ml plant Dry Matter Percent Green W plant Dry gm\/ plant 90\/75 90\/60 75\/60 6.10b 7.75b 14.62a 1.68a 1.93a 3.13a 27.42a 24.90a 21.22a 7.81b 6.95b 20.90a 1.16b 1.03b 3 .39a Temp. O p Pods\/ Plant Number Peas\/ Pod Number Pod F i r s t Pairs\/Plant Flowering Number Node 90\/75 90\/60 75\/60 4.8 b 3.8 b 9.7 a 2.9 b 4.5 a 3.2 b 0 c 6.4 b 3.4 a 18.8 b 15.8 a 15.2 a Yine Green Dry gm\/ gm\/ plant plant 18.56ab 2.25ab 13.77b 2.41b 33.64a 5.89a Plants with 1 T i l l e r s Proportion 1\/8 b 6 b 6\/8 a i 27. i n the f i r s t experiment. In the t h i r d experiment, green and dry weights were higher at 70\/60\u00b0F than at 85\/70 or 85\/60\u00b0F except f o r dry weights at f u l l bloom which were not s i g n i f i c a n t l y d i f f e r e n t (Table 6). Differen-ces i n percent dry matter among plants growing at d i f f e r e n t tem-peratures were demonstrated at a l l stages except at the tenth node, with the percent dry matter lower at the lower temperature. Plant, height was greater at 70\/60\u00b0]?. The time to each growth stage was longest at 70\/60\u00b0F and shortest at 85\/60\u00b0F. Pod weights and vine weights were s i m i l a r l y affected by 85\/70 and 85\/60 and were greater at 70\/60\u00b0F, while pea y i e l d was s i m i l a r l y affected by 85\/60 and 70\/60\u00b0F with l e s s y i e l d a t 85\/70\u00b0F (Table 7). Numbers of pods per plant and pod pairs per plant were highest at 70\/60\u00b0F but number of peas per pod were reduced only at 85\/70\u00b0F. The f i r s t flowering node was higher at 85\/70\u00b0 than at other temperatures. Plants t i l l e r e d at a l l temperatures. No differences were demonstrated i n the effects of 70\/60, 70\/55, and 70\/50\u00b0F on t o t a l growth at any stage i n the fourth experiment (Table 8). Among growth components at maturity har-vest, only green and dry pea y i e l d s were higher at 70\/55\u00b0 than at 70\/50\u00b0F (Table 9). No other s i g n i f i c a n t differences between these temperatures were demonstrated. In the f i f t h experiment green and dry weights of plants and plant height progressively decreased as the day temperatures i n -creased, while the opposite was true f o r the number of days to a growth stage (Table 10). Percent dry matter was occasionally higher at higher temperatures. More growth by plants at 70\/50\u00b0F than those at 70\/60\u00b0F was demonstrated at the s i x t h node and matur-38 Table 6. Total growth of pea plants grown at 85\/70, 85\/60 and 70\/60\u00b0F day\/night temperatures. Third experiment. Growth Stage Temp. \u00b0F Days to Growth Stage Green Weight gm\/plant Dry Weight gm\/plant Dry Matter Percent Plant Height Inches Sixth 85\/70 20 2.06 b 0.24 b 11.37 b node 85\/60 20 1.98 b 0.23 b 11.61 b 70\/60 22 3.61 a 0.34 a 9.22 a Tenth 85\/70 28 6.13 b 0.65 b 10.57 a node 85\/60 29 6.14 b 0,63 b 10.65 a 70\/60 33 13.06 a 1.12 a 8.55 a F u l l 85\/70 45 22.60 b 2.92 a 12.90 b bloom 85\/60 42 19.85 b 2.90 a 14.52 c 70\/60 47 37.90 a 3.87 a 10.19 a Maturity 85\/70 63 41.96 b 7.75 b 18.47 b 28.8 b 85\/60 59 39.92 b 7.79 b 19.41 b 23.0 b 70\/60 72 84.44 a 14.35 a 16.99 a 39.0 a 39. Table 7. Growth components at maturity harvest of pea plants grown at 85\/70, 85\/60 and 70\/60\u00b0F day\/night tempera-tures. Third experiment. Peas Pods Vine Temp. \u00b0F 85\/70 85\/60 70\/60 Green gm\/ plant ' 8.78b 12.66a 15.16a Dry gm\/ plant 2.21b 3.23a 2.99a Dry Matter Percent 24.71b 25.41b 19.74a Green Dry gm\/ gm\/ plant plant 9.94b 1.47b 9.67b 1.43b 29.46a 4.39a Green Dry gm\/ gm\/ plant plant 23.24b 17.59b 39.82a 4.07b 3.13b 6.97a Temp. Pp 85\/70 85\/60 70\/60 Pods\/ Plant Number 5.9 b 6.3 b 10.8 a Peas\/ 'Pod Number 3.4 b 4.1 a 3.6 ab Pod Pairs\/Plant Number 0.6 b 1.9 ab 3.5 a F i r s t Flowering Node 18.9 b 16.0 a 14.9 a Plants with T i l l e r s Proportion 8\/8 a 7\/8 a 8\/8 a 40 Table 8. Total growth of pea plants grown at 70\/60, 70\/55 and 70\/50\u00b0F day\/night temperatures. Fourth experiment. Growth Stage Temp, op Days to Growth Stage Green Weight gm\/plant Dry Weight gm\/plant Dry Matter Percent Plant Height Inches Sixth 70\/60 18 4.08 a 0.42 a 10.17 a node 70\/55 18 3.65 a 0.40 a 10.94 a 70\/50 19 3.97 a 0.40 a 10.17 a Tenth 70\/60 26 11.23 a 1.10 a 9.80 a node 70\/55 27 13.57 a 1.30 a 9.58 a 70\/50 28 12.85 a 1.23 a 9.57 a F u l l 70\/60 43 33.32 a 3.63 a 10.89 a bloom 70\/55 43 44.11 a 4.41 a 10.00 a 70\/50 45 43.51 a 4.51 a 10.36 a Maturity 70\/55 63 73.23 a 12.76 a 17.43 a 41.1 a 70\/50 65 74.35 a 12.64 a 17.00 a 42.5 a 41 Table 9. Growth, components at maturity harvest of pea plants grown at 70\/60, 70\/55 and 70\/50\u00b0F day\/night tempera-tures. Fourth experiment. Temp. \u00b0F 70\/55 70\/50 Green gm\/ plant 17.65a 14.63b Peas Pry gm\/ plant 3.78a 2.90b Dry Matter Percent 21.42a 19.82a Pods Green Dry gm\/ gm\/ plant plant Vine 20.64a 21.19a 2.86a 2.98a Green Dry gm\/ gm\/ plant plant 34.94a 38.63a 6.12a 6.76a Temp. 9F 70\/55 70\/50 Pods Plant Number 8.9 a 9.0 a Peas\/ Pod Number 4.0 a 3.6 a Pod Pairs\/Plant Number 4.0 a 3.9 a F i r s t Flowering Node 15.8 a 15.9 a Plants with T i l l e r s Proportion 8\/8 a 7\/8 a 42. Table 10. Total growth of pea plants grown at 90\/60, 85\/60, 80\/60, 75\/60, 70\/60 and 70\/50\u00b0F day\/night tempera-tures. F i f t h experiment. Days to Green Dry Dry Plant Growth Temp. Growth Weight Weight Matter Height Stage Pp Stage gm\/plant gm\/plant Percent Inches Sixth 85\/60 17 1.66 d 0.18 e 10.84 a node 80\/60 17 2.27 c 0.24 d 10.57 a 75\/60 19 3.36 b 0.33 c 9.82 a 70\/60 19 3.38 b 0.35 b 10.36 a 70\/50 20 3.79 a 0.41 a 10.82 a Tenth 85\/60 25 5.80 c 0.70 c 12.07 b node 80\/60 25 7.64 be 0.76 c 9.95 a 75\/60 28 9.97 b 0.97 b 9.73 a 70\/60 30 13.77 a 1.37 a 9.95 a 70\/50 30 14.31 a 1.30 a 9.08 a F u l l 90\/60 38 7.07 d 1.17 c 16.55 b bloom 85\/60 38 12.80 cd 1.73 c 13.52 a 80\/60 41 17.31 be 2.82 b 16.29 b 75\/60 42 21.67 b 2.82 b 13.01 a 70\/60 45 31.29 a 4.21 a 13.44 a 70\/50 45 37.08 a 4.65 a 12.54 a Maturity 90\/60 50 16.08 e 2.83 e 17.60 a 15.1 d 85\/60 52 23.90 d 4.26 d 17.82 a 19.2 d 80\/60 56 38.89 c 6.89 c 17.72 a 25.7 c 75\/60 58 31.99 c 6.23 c 19.47 a 26.7 be 70\/60 62 56.58 b 10.55 b 18.65 a 30.8 b 70\/50 69 72.48 a 12.54 a 17.30 a 37.0 a 43% i t y stages. G-reezi and dry weights of peas decreased with increasing tem-perature from 70\/50 or 70\/60 to 90\/60\u00b0F i n the f i f t h experiment (Table 11). Pod and vine dry weights also decreased with increas-ing temperature. Numbers of pods and pod pairs per plant also de-creased with increasing temperature while numbers of peas per pod and f i r s t flowering node were not a f f e c t e d by temperature. T i l -l e r i n g ranged from a l l plants t i l l e r i n g at the lower temperatures to no t i l l e r i n g at the higher temperatures. Total weights of plants were s i m i l a r l y affected by tempera-ture i n the s i x t h experiment, exeepXaiL the maturity harvest f o r which growth at 60\/50\u00b0F exceeded that at 65\/55 or 65\/50\u00b0P (Table 12). Differences-in t o t a l dry weights were demonstrated at a l l stages except the tenth node, with most growth a t 60\/50 GF. No differences i n percent dry matter or plant height were demonstrated. Differences i n pod green and dry weights and vine dry weights were demonstrated with highest values at the lowest temperatures (Table 13). No differences i n any other growth components were demonstrated. Almost a l l plants t i l l e r e d at the temperatures used i n t h i s experiment. Dry weights of plants were higher at 45\/40\u00b0F than 55\/40\u00b0F fo r a l l three harvests i n the seventh experiment (Table 14). The 55\/40\u00b0F plants had a lower percent dry matter, consequently no differen c e s i n green weights were demonstrated. There was increased t i l l e r i n g at the lower temperature. At both temperatures there were many plants with more than one t i l l e r per plant. In a l l other experiments, conducted at higher temperatures, there was usually not more than one t i l l e r per plant, i f any. There was a marked 44. Table 11. Growth components at maturity harvest of pea plants grown at 90\/60, 85\/60, 80\/60, 75\/60, 70\/60 and 70\/50\u00b0P day\/night temperatures. F i f t h experiment. Temp. 90\/60 8'5\/60 80\/60 75\/60 70\/60 70\/50 leas Pods Vine Green \"gm\/ plant Dry gm\/ plant Dry Matter Percent Green gm\/ plant Dry gm\/ plant Green gm\/ plant Dry gm\/ plant 5.79d 6.64c 11.28b 9.10b 15.89a 16.37a 0).84c 1.57c 2.60ab 2.32b 3.33a 3.34a 22.15a 23.69a 23.04a 25.51a 20.94a 20.42a *3.21d 4.67d 9.68c 7.07c 13.95b 21.14a 0?.49d 0.73d 1.44c 1.11c 2.21b 3.05a 9.08d 12.59d 17.93c 15.82c 26.74b 34.97a 1.50d 1.96d 2.85c 2.80c 5.01b 6.15a Pods\/ Temp. Pliant \u00b0,F Number 90\/60 85\/60 80\/60 75\/60 70\/60 70\/50 2.1 3.0 4.8 4.6 6.9 10.0 d d c c b a Peas\/ P^d Number 4.3 a 4.7 a 4.8 a 3.5 a 4.5 a 3.6 a Pod Pairs\/Plant Number 0.0 0.2 1.4 1.8 3.5 4.3 c c b b a a F i r s t Flowering Node 15.3 16.2 15.4 15.6 15.9 15.5 a a a a a a Plants with T i l l e r s Proportion 0\/8 0\/8 2\/8 6\/8 8\/8 8\/8 45 Table 12. Total growth, of pea plants grown at 65\/55, 65\/50 and 60\/50\u00b0P day\/night temperatures. Sixth experiment. G-rowth Stage ;-Temp. \u00b0P Bays to Growth Stage Green Weight gm\/plant Bry Weight gm\/plant Bry Matter Percent Plant Height Inches Sixth 65\/55 20 3.00 a 0.31 b 10.25 a node 65\/50 21 3.32 a 0.36 ab 10.84 a < 60\/50 25 3.92 a 0.43 a 10.83 a -Tenth 65\/55 31 11.63 a 1.22 a 10.49 a node 65\/50 32 12.75 a 1.36 a 10.65 a 60\/50 35 14.30 a 1.45 a 10.13 a P u l l 65\/55 48 42.71 a 4.82 b 11.29 a bloom 65\/50 48 43.25 a 5.22 ab 12.06 a 60\/50 57 48.53 a 6.34 a 13.07 a Maturity 65\/55 80 124.51 b 21.77 b 17.48 a 45.6 a 65\/50 81 119.37 b 20.39 b 17.08 a 46.7 a 60\/50 109 169.59 a 30.62 a 18.06 a 50.1 a 46 Table 13. Growth components at maturity harvest of pea plants grown at 65\/55, 65\/50 and 60\/50\u00b0F day\/night tempera-tures. Sixth experiment. Peas Temp. ?F 65\/55 65\/50 60\/50 Green gm\/ plant 21.97a 19.71a 28.06a Dry plant 4.87a 4.07a 6.56a Pry Matter Percent 22.14a 20.60a 23.06a Pods Green Dry gm\/ gm\/ plant plant 46.23b 6.57b 42.91c 6.20b 62.16a 8.92a Vine Green Dry gm\/ gm\/ plant plant 56.31a 56.75a 79.37a 10.33b 10.12b 15.14a Temp. Pp 65\/55 65\/50 60\/50 Pods\/ Plant Number 12.6 a 12.1 a 17.0 a Peas\/ Pod Number 3.8 a 4.0 a 4.0 a Pod Pairs\/Plant Number 4.9 a 5.3 a 6.6 a F i r s t Flowering Node 14.8 a 14.9 a 15.0 a Plants with T i l l e r s Proportion 7\/8 a 7\/8 a 7\/8 a 47. Table 14. Total growth of pea plants grown at 55\/40 and 45\/40\u00b0P day\/night temperatures. Seventh experiment. Growth Stage Temp. Pp Days to Growth Stage Green Weight gm\/plant Dry Weight gm\/plant Dry 'Matter Percent Sixth node 55\/40 45\/40 40 65 1 5.06 a 7.27 a 0.58 b 1.00 a 11.50 b 13.74 a Tenth node 55\/40 45\/40 59 101 18.46 a 18.10 a 1.92 b 2.82 a 10.41 b 15.63 a P u l l bloom 55\/40 45\/40 75 129 46.91 a 49.87 a 5.64 b 7.53 a 12.03 a 15.10 a Growth Stage Temp. O p F i r s t T i l l e r s \/ Flowering per plant Node Plant * Height P u l l bloom 55\/40 45\/40 1.5 3.0 13.3 14.5 19.8 16.8 * Measured to the 13th node. 48. retardation of development and the plants were shorter at the lower temperature. This experiment had to be terminated because of a breakdown of the a i r conditioning unit i n the 55\/40\u00b0P cabinet at the early f r u i t i n g stage. A freezing temperature resulted and the plants were damaged. However, the plants were l e f t to develop at 55\/40\u00b0F a f t e r the a i r conditioner was repaired. Number of pods per plant and peas per pod were l a t e r determined and found to be surprisingly high. The two r e p l i c a t i o n s averaged 11.6 pods per plant and 4.5 peas per pod. In the eigth experiment no effects of s h i f t i n g plants from 75\/60 to 80\/60\u00b0F could be demonstrated u n t i l the maturity har-vest, except f o r plant height which was l e s s a f t e r s h i f t i n g (Table 15). A longer time at the elevated temperature resulted i n shorter plants. The longer the duration of the high temperature treatment, the lower were the t o t a l green and dry weights and the shorter the plants at maturity harvest. Pea and pod y i e l d s were reduced by exposure to 85\/60\u00b0P from the s i x t h node to maturity (Table 16). Vine green and dry weights were progressively reduced by longer exposure to the higher temperature. Number of pods and pod pairs per plant and the f i r s t flowering node were a l l reduced i f plants were shifted at the s i x t h node to 85\/60\u00b0P, compared to s h i f t i n g at l a t e r stages. In the ninth experiment, almost no effect of s h i f t i n g plants from 75\/60 to 85\/60\u00b0F f o r li m i t e d periods could be demonstrated (Tables 17 and 18). The only s i g n i f i c a n t effect was an increased number of peas per pod with s h i f t i n g of plants to the higher tern-49 Table 15. Total growth of pea plants started at 57\/60\u00b0P day\/ night temperatures and shifted to 85\/60\u00b0F at the sixth, tenth or experiment. f i f t e e n t h node stages. Eighth Growth Stage Temp. O p * Days to Growth Stage Green Weight gm\/plant Dry Weight gm\/plant Dry Matter Percent Plant Height Inches Sixth node i 75\/60 18 3.41 0.34 i 9.87 Tenth node 75\/60 A 26 26 13.66 a 11.78 a 1.25 a 1.14 a 9.13 a 9.66 a F u l l bloom 75\/60 A B 37 36 36 28.64 a 23.74 a 28.90 a 2.95 a 2.48 a 3.07 a 10.24 a 10.40 a 10.56 a 24.3 a 20.4 c 22.5 b Maturity A B C 54 55 58 42.98 c 53.39 b 57.79 a 7.83 c 9.59 b 10.87 a 18.22 b 17.96 a 18.81 c 26.6 c 30.1 b 33.0 a * Plants subjected to 85\/60\u00b0F from A sixth node B tenth node C f i f t e e n t h node. 50 Table 16. Growth components at maturity harvest of pea plants started at 75\/60\u00b0F day\/night temperatures and shifted to 85\/60\u00b0F at the sixth, tenth or f i f t e e n t h node stages. Eighth experiment. Peas Pods Vine Green Dry gm\/ gm\/ plant plant Dry Matter Percent Green gm\/ plant Dry gm\/ plant Green m\/ plant gm\/ plant A B C 11.68b 2.62b 12.77ab 2.84ab 14.96a 3.74a 22.43a 22.24a 25.00b 9.33b 13.42a 13.57a 1.47b 1.99a 2.01a 21.37c 27.20b 29.26a 3.74c 4.76b 5.12a Temp. Oj> Pods\/ Plant Number Peas\/ Pod Number Pod Pairs\/Plant Number F i r s t Flowering Node A B G 6.4 b 9.0 a 8.6 a 4.0 a 3.4 b 3.8 a 2.8 b 4.0 a 3.8 a 15.6 b 16.7 a 16.2 a * Plants subjected to 85\/60\u00b0F from A sixth node to maturity B tenth node to maturity C f i f t e e n t h node to maturity Table 17 51 Total growth of pea plants grown at 75\/60 F day\/night temperatures and shifted to 85\/60\u00b0F at cert a i n growth stages. Ninth experiment. Green Dry Dry Plant Temp. Days to Weight Weight Matter Height Treatment* Maturity gm\/ plant am\/plant Percent Inches A 65 53.66 a 9.58 a 17.85 a 39.4 a B 65 61.44 a 10.73 a 17.46 a 41.3 a C 65 47.06 a 8.42 a 17.89 a 36.8 a D 58 51.36 a 8.82 a 17.17 a 34.3 a * Plants subjected to 85\/60\u00b0 F treatment from A seeding,to the sixth node stage B sixth to the tenth node stage C tenth to the f i f t e e n t h node stage D f i f t e e n t h node stage to plus ten days. 52. Table 18. Growth, components at maturity harvest of pea plants grown at 75\/60\u00b0F day\/night temperatures and shifted to 85\/60\u00b0P at certain growth stages. Ninth experiment. Peas Pods Vine Green gm\/ Dry ml Dry Matter Green ml Dry gm\/ Green ml Dry ml Temp.* plant plant Percent plant plant plant plant A B C D 10.91a 12.81a 10.14a 10.22a 2.51a 2.71a 2.31a 2.01a 22.97a 21.16a 22.76a 19.67a 15.26a 18.14a 12.84a 14.61a 2.26a 2.56a 1.90a 2.16a 27.50a 30.49a 24.08a 26.53a 4.64a 4.21a 5.34a 4.81a Pods\/ Peas\/ Pod F i r s t Temp. Plant 'Pod Pairs\/Plant Flowering \u00b0F Number Number Number Node A' 8.3 a 2.8 b 2.5 a 17.3 a B 10.1 a 2.8 b 2.9 a 16.1 a C 6.9 a 2.9 b 2.0 a 17.4 a D 6.8 a 4.1 a 2.6 a 16.4 a * Plants subjected to 85\/60\u00b0F treatment from A seeding to the six t h node stage B si x t h to the tenth node stage C tenth to the f i f t e e n t h node stage D f i f t e e n t h node stage to plus ten days. 53. perature at the time of flowering ( f i f t e e n t h node plus ten days). o When plants were shifted from 70\/60 to 90\/60 P or vice versa i n the tenth experiment, differences i n percent dry matter and plant height were demonstrated (Table 19). Percent dry matter increased with s h i f t i n g from low to high temperature while height decreased. There were more pod pairs and t i l l e r s on plants shifted to the high temperature from the low temperature (Table 20). A summary of rates of dry matter accumulation (Table 21) f o r a l l except the s h i f t i n g experiments showed that temperature r e-quirement f o r maximum rates up to the s i x t h node was approximately 70\/50 to 70\/60\u00b0P, up to the tenth node 60\/50 to 75\/60\u00b0F, up to f u l l bloom, 60\/50 to 70\/60\u00b0P and up to maturity, 60\/50 to 70\/60\u00b0P. A summary of rate of node development (Table 22) f o r a l l except Experiment 1 and the s h i f t i n g experiments showed that the development rate f o r a p a r t i c u l a r temperature under controlled-environment conditions was very constant as indicated by the very high l i n e a r correlations of node stage and time between the f i f t h node and f u l l bloom stages. The regression c o e f f i c i e n t s i n d i c a t -ing the number of nodes developed per day ranged from 0.154 to 0.561. The rate of development was severely retarded at the very low temperatures but was quite similar over a wide range of higher temperatures. In general, the rate of development i n -creased as the temperature increased. A summary of internode length f o r representative internodes (Table 23) showed that the length of the six t h and tenth i n t e r -nodes decreased with increasing temperature. Internode lengths were also s l i g h t l y shorter at the very low temperatures. Longest si x t h and tenth internodes were generally i n the 60\/50 to 75\/60\u00b0P 54. Table 19. Total growth of pea plants started at 70\/60\u00b0F or 90\/60\u00b0F day\/night temperatures and shifted to 90\/60\u00b0F or 70\/60\u00b0F at the thirteenth node. Tenth experiment. Green Dry Dry Plant Temp. Days to Weight Weight Matter Height Treatment Maturity gm\/nlant gm\/plant Percent Inches A* 55 53.20 a 6.61 a 19.93 b 27.8 b B 72 55.50 a 9.73 a 17.51 a 36.3 a * A Plants shifted from 70\/60\u00b0F to 90\/60\u00b0P at the 13th node stage. B Plants shifted from 90\/60\u00b0F to 70\/60\u00b0P at the 13th node stage. 55 Table 20. Growth components at maturity harvest of pea plants started at 70\/60\u00b0P or 90\/60\u00b0F day\/night temperatures and shifted to 90\/60\u00b0F or 70\/60\u00b0F at the thirteenth node. Tenth experiment. Temp. A* B Green m\/ plant 7.90a 13.03a Peas Dry ml plant 1.94a 3.22a Dry Matter Percent 24.59a 24.71a Pods Green Dry gm\/ gm\/ plant plant 6.90a 16.60a 1.12a 2.07a Vine Green Dry gm\/ gm\/ plant plant 18.40a 3.55a 25.87a 4.38a Temp, . O P Pods\/ Plant Number Peas\/ Pod Number Pod Pairs\/Plant Number F i r s t Flowering Node Plants with T i l l e r s Proportion A B 6.4 a 6.5 a 2.8 a 3.6 a 1.8 a 0.5 b 15.5 a 15.3 a 8\/8 a 0\/8 b * A Plants shifted from 70\/60\u00b0F to 90\/60\u00b0F at the 13th node stage. B Plants shifted from 90\/60\u00b0F to 70\/60\u00b0F at the 13th node stage. 56. Table 21 Dry matter accumulation rates of pea plants as influenced by temperature. Grams dry matter\/day. (Computed from: dry weight at a growth stage divided by number of days from planting to that stage.) Growth Stage \u00b0F Sixth Tenth\" F u l l ' Maturity Temperature Node Node Bloom Vine Whole Plant Experiment 1 90\/75 90\/60 75\/60 .013 \" .012 .019 .017 .018 .033 .045 .041 .063 .045 .031 .067 .079 .056 .141 Experiment 2 90\/75 90\/60 75\/60 .011 .012 .019 .020 .021 .040 .039 .045 .083 .054 .045 .093 .095 .086 .174 Experiment 3 85\/70 85\/60 70\/60 .012 .012 .015 .023 .022 .034 .065 .069 .082 .065 .053 .097 .123 .132 .200 Experiment 4 70\/60 70\/55 70\/50 .023 .022 .021 .042 .048 .044 .084 .103 .100 .097 .104 .193 .194 Experiment 5 90\/60 85\/60 80\/60 75\/60 70\/60 70\/50 .010 .013 .017 .018 .020 .027 .029 .033 .044 .042 .030 .044 .044 .066 .092 .101 .030 .038 .051 .048 .081 .089. .057 .082 .123 .107 .170 .182 Experiment 6 65\/55 6-5\/50 60\/50 .016 .017 .017 .039 .043 .041 .100 < .109 .111 .129 .125 .139 .272 .252 .281 Experiment 7 55\/40 45\/40 .015 .015 .033 .028 .075, .058 -mm 57. Table 22. Node development and stem elongation rates of pea plants from approximately the f i f t h node to f u l l bloom stages as influenced by temperature. Linear regression analysis, where Y=node stage, 2fc=time i n days. \u00b0,p Number of Regression Correlation Stem * Temperature Observations Coefficient Coefficient Elongation Experiment 2 90\/75 90\/60 75\/60 9-9 11 0(. 561 0.516 0.451 0.999 0.999 0.999 12.3 15.4 20.6 Experiment 3 85\/70 85\/60 70\/60 11 11 12 0.533 0.481 0.417 1.000 1.000 0.995 15.3 16.6 20.5 Experiment 4 70\/60 70\/55 70\/50 13 13. 13 0.495 0.461 0.442 0.998 0.999 0.999 25.6 25.4 Experiment 5 90\/60 85\/60 80\/60 75\/60 70\/60 70\/50 13 14 15 17 19 19 0.495 0.521 0.485 0.471 0.428 0.389 0.998 0.999 1.000 0.999 0.999. 0.999 13.5 15.7 19.2 20.5 22.5 23.2 Experiment 6 65\/55 65\/50 60\/50 21 22 23 0.407 0.399 0.372 0.999 0.997 0.998 24.0 24.5 22.5 Experiment 7 55\/40 45\/40 15 17 0.254 0.154 0.998 0.998 14.7 6.5 * Stem elongation: average elongation i n mm\/day from the f i f t h to the f i f t e e n t h node stages. 58. Table 23. Intermode lengths of pea plants as influenced by-temperature, mm. \u00b0F Sixth Tenth F u l l Bloom* Temperature Ihternode Internode Intemode Experiment 1 \u202290\/75 19 24 47 90\/60 25 32 35 75\/60 32 35 59 Experiment 2 90\/75 20 20 51 90\/60 25 28 53 75\/60 36 45 73 Experiment 3 85\/70 27 30 47 85\/60 31 38 43 70\/60 41 47 81 Experiment 4 70\/55 49 60 49 70\/55 50 56 87 Experiment 5 90\/60 26 30 25 85\/60 28 32 38 80\/60 33 40 58 75\/60 44 42 71 70\/60 45 51 66 70\/50 52 61 91 Experiment 6 65\/55 46 55 107 65\/50 48 55 109 60\/50 54 55 110 Experiment 7 55\/40 39 54 94 45\/40 42 47 42 * Internode below f i r s t flowering node. 59. temperature range. The internode below the f i r s t flowering node was very long at 55\/40 to 70\/50\u00b0F but was much shorter at higher temperatures and at the very low 45\/40\u00b0F temperature. 60. DISCUSSION These experiments have indicated the nature of some effects of temperature on the growth and development of Dark Skin Perfec-t i o n peas. Temperature affected f r u i t and vine y i e l d , rates of stem elongation and node development, position of the f i r s t flower and t i l l e r i n g . The rate of development of the pea plant, i n terms of nodes produced per day averaged over the period from f i f t h to f i f t e e n t h nodes, increased steadily as temperature increased. Regression c o e f f i c i e n t s ranged from 0.154 to 0.561 node per day at 45\/40 and 90\/75 GF, respectively. The change i n rate of development was approximately proportional to the average temperature in d i c a t i n g that night temperature was as ef f e c t i v e as day temperature. Went (1957) found that day temperature was as ef f e c t i v e as night tem-perature i n a f f e c t i n g the rate of node development, and node de-velopment had a constant rate up to the time of flowering. Days to the sixth node increased slowly with decreasing tem-perature from as low as 16 days at 90\/75\u00b0F to 21 days at 65\/50\u00b0F, and then increased mardedly at temperatures below 65\/50 GF. These time periods r e f l e c t , i n part, the temperature requirements f o r germination. Kotowski (1926) reported that the speed of germina-t i o n of peas increased as the temperature was increased from 40 to 78\u00b0F, but was no fas t e r at 86\u00b0F. Differences i n days to tenth node and f u l l bloom stages among temperatures were a r e f l e c t i o n of days to the s i x t h node plus the rate of node development. The extent of the differences due to temperature increased slowly i n progressing from one growth stage to another. Boswell (1926) also found a close i n -61. verse relationship between the time of development to a given stage and the mean temperature occurring during that period. Days to pea maturity increased with decreasing temperature from as low as 53 days at 90\/60\u00b0F to 109 days at 60\/50\u00b0F. The high day and high night temperature treatments, 90\/75 and 85\/70\u00b0F delayed time to maturity as compared to 90\/60 and 85\/60\u00b0]?. This delay was due mainly to a s h i f t i n the position of the f i r s t flower to a higher node, from node 15-16 at 90\/60\u00b0F to node 19-20 at 90\/75\u00b0F and from node 16 at 85\/60\u00b0F to node 19 at 85\/70\u00b0F. This high temperature effect on number of nodes to the f i r s t flower can be contrasted with the vern a l i z a t i o n effect reported by various investigators. When f u l l y imbibed pea seeds were sub-jected to a cold temperature treatment during germination, the number of nodes to the f i r s t flower was reduced (Leopold and Guernsey, 1953, 1954; Highkin, 1956; Moore and Bonde, 1962; Nakamura et a l . , 1962). The vern a l i z a t i o n effect could be n u l l i -f i e d , however, by a high temperature treatment applied immediately a f t e r the v e r n a l i z a t i o n treatment (Highkin, 1956). In the experiments reported here, the number of nodes to the f i r s t flower was lowest at 55\/40\u00b0F (node 13) and highest at 90\/75\u00b0F (node 20). These r e s u l t s are i n agreement with the l i t e r -ature referred to above and may be variously interpreted as due to destruction of a flower-promoting substance at high temperatures (Moore and Bonde, 1962), destruction of a flower-inhibiting sub-stance at low temperatures (Barber, 1959) or a balance or i n t e r -action between auxin and some other plant constituent (Leopold and Guernsey, 1953). It i s int e r e s t i n g to note that an increase i n the number of nodes to the f i r s t flower also occurs when peas are grown under 62. a short photoperiod (Nakamura, 1962). Plant height was progressively reduced as temperature i n -creased from 60\/50 to 90\/60\u00b0F with the exception of those plants grown under the high night-plus high day-temperature regimes. Plant height was greater at 90\/75 and 85\/70\u00b0F than at 90\/60 or 85\/60\u00b0F due to the increase i n number of nodes to the f i r s t flower as previously noted. Plant height was also decreased at temperatures below 60\/50\u00b0F. Thus, 60\/50\u00b0F or a mean temperature of 55\u00b0F was the optimum temperature f o r growth i n length of the stem. These re s u l t s agree with experiments reported by Went (1957), who found that length of Alaska pea stems was reduced as the night temperature was increased from 4\u00b0C (39\u00b0F) to 26\u00b0C (79\u00b0F). The day temperature was held constant at 23\u00b0C (73\u00b0F). The o p t i -mum mean temperature, therefore, was 56\u00b0F. Went pointed out that the optimum temperature shifted from 23\/17 to 23\/4\u00b0C a f t e r two months of growth, and t h i s s h i f t was not due to differences i n growth rate but only to d i f f e r e n t i a l growth cessation associated with the onset of f r u i t i n g . Measurement of internode lengths at the maturity harvest revealed that, generally, internode length increased i n going from node one to the f u l l bloom node, and decreased thereafter. In contrast, Went (1957) found that from the seventh node on the f i n a l length of Alaska pea internodes became constant. There was often a sharp r i s e i n internode length f o r the internode below the f i r s t flower, associated with the occurrence of f r u i t set. F r u i t set i s associated with an increase i n the amounts of endogenous auxins, which may stimulate o v e r a l l plant growth (Leopold, 1955). The-effects of temperature on internode length-and plant 63.. . height p a r a l l e l e d one. another_&s.jfOuld be expected since plant height i s the summation of in d i v i d u a l internode lengths. The i n h i b i t i n g effect of high temperature on internode length was p a r t i c u l a r l y s t r i k i n g i n the case of the internode below the f i r s t flower. This suggests destruction of auxin or suppression of auxin formation at high temperatures. Leopold (1955) c i t e s ex-periments which showed that exposure of r i c e seedlings to warm temperatures (26\u00b0C) produced s t r i k i n g reductions of auxin content when compared to seedlings grown at cool temperatures (10\u00b0C). Plant height i s also a r e f l e c t i o n of the rate of stem elonga-t i o n . In the present experiments rate of stem elongation decreased above and below an average temperature of 62\u00b0F (70\/55\u00b0F), with marked reductions occurring above 70\u00b0P (80\/60\u00b0F) and below 55\u00b0F (60\/50\u00b0F). Changes i n night temperature of f i v e to ten degrees at the lower temperature range, 70\/60 to 60\/50\u00b0F, had l i t t l e e ffect on rate of elongation; whereas sim i l a r increases i n the day temperature at 40\u00b0 and 50\u00b0F night temperatures resulted i n increases i n elongation rate. In contrast, increases i n night temperature at the higher temperature range, 85\/60 to 90\/60\u00b0F r e -sulted i n reductions i n rate of elongation, the extent of the reduction increasing with the degree of temperature change. r These r e s u l t s are i n agreement with those of Went (1957), who found that with night temperature held constant at 14\u00b0C (57\u00b0F), the optimum day temperature f o r rate of stem elongation of Alaska peas was 23\u00b0C (73\u00b0F). The optimum mean temperature, there-fore, was 65\u00b0F. He also found that when day temperature was held constant at 20\u00b0C (68\u00b0F), changes i n night temperature over the range 7\u00b0C (45\u00b0F) to 20\u00b0C (68\u00b0F) had no effect on rate of elonga-64. t i o n . Increasing the night temperature above 20\u00b0C, however, de-creased rate of elongation. Vine y i e l d at a given growth stage generally decreased as temperature increased. The extent of. differences i n vine weight was greater at the l a t e r growth stages, which indicates that the temperature effect was cumulative and\/or that the optimum tempera-ture f o r stem growth decreased as the age of the plant increased. On a d r y matter accumulation per day basis, which eliminated d i f -ferences i n vine weight due to days to growth stage, vine growth decreased above and below a temperature optimum ranging from about 70\/60\u00b0F at the s i x t h node stage to 60\/50\u00b0F at maturity. These r e s u l t s agree with those of Went (1957), who found that green and dry weight of the whole plant was affected exactly l i k e stem elongation, which reached an optimum at about 65\u00b0F. Went also found that the optimum temperature f o r rate of stem growth shifted from higher to lower temperatures i n the course of plant development. T i l l e r i n g , i . e . the formation of secondary stems, was most p r o l i f i c a t the very low temperatures and decreased or was absent as temperature increased. This phenomenon probably accounted f o r part of the reduction i n vine y i e l d observed at high temperatures. Vine weight was greater at 90\/75 than at 90\/60\u00b0F because of the s h i f t i n p o s i t i o n of the f i r s t flower which resulted i n an increase i n plant height. The same s h i f t i n flowering node occur-red at 85\/70 compared to 85\/60\u00b0F. At 55\/40\u00b0F, however, flower-ing began at a lower node than at other temperatures and vine y i e l d at the f u l l bloom stage was lower than wouldbe expected, on the basis of vine y i e l d s produced at the e a r l i e r growth stages. 65. The rate of dry matter accumulation f o r the whole plant i n -creased steadily i n the course of development, r e f l e c t i n g the i n -crease i n plant size and consequent increase i n photosynthate-producing ti s s u e . The rate of dry matter accumulation i n the stem, however, increased r e l a t i v e l y l i t t l e or, i n some cases, decreased as the plant developed from f u l l bloom to maturity. This correla-t i o n between vegetative and reproductive growth i s generally be-lieved to result from a monopolization of nitrogenous and\/or carbohydrate food materials by the developing f r u i t (Meyer et a l . , I960). Percent dry matter of plants was markedly increased at the lowest temperature used i n these experiments (45\/40\u00b0F). This result can be explained by the fact that low temperatures cause a reduction i n absorption and movement of water i n plants (Jensen and Taylor, 1961). This same phenomenon may also account, at least i n part, f o r the reduction i n rate of dry matter accumula-t i o n which occurred below 60\/50\u00b0F. Brouwer (1962), f o r example, found that the growth of peas was lim i t e d by water deficiency at root temperatures below 59\u00b0F. Percent dry matter was also i n -creased i n some experiments, at the higher temperatures. This result was probably due to an increased rate of transpiration. Pea y i e l d i s a function of pods per plant, peas per pod and the weight of in d i v i d u a l peas. In the present experiments, pea y i e l d was generally affected more by pods per plant than by peas per pod. The number of pods per plant decreased markedly as the temperature increased, due mainly to a decrease i n the number of pod pairs per plant and par t l y to a decrease i n the number of nodes which produced pods. These re s u l t s agree with those of Boswell (1926), who found that, as temperatures rose, pea y i e l d 66. f e l l r apidly, due larg e l y to a reduction i n the number of pods per plant. Peas were not always harvested at exactly the same stage of maturity as i s indicated by differences i n percent dry matter of peas. In a few cases, \" s i g n i f i c a n t \" differences i n pea y i e l d probably resulted from differences i n pea maturity. In those experiments i n which one temperature regime was im-posed from seeding to maturity, peas per pod was not s i g n i f i c a n t l y affected by temperature except at 90\/75\u00b0F and 85\/70\u00b0F. At these temperatures peas per pod was reduced i n comparison to 90\/60 and 85\/60\u00b0F. At 90\/75\u00b0F an increase i n pods per plant partly compen-sated f o r the reduction i n peas per pod. It should be mentioned that the number of peas per pod pro-duced by plants i n a l l experiments averaged only about 45 percent of the pote n t i a l maximum of eight peas per pod. Also, the pod at the f i r s t bloom node generally contained more peas than pods at higher nodes. Similar failures._ojf..maximum development of peas per pod i n Alaska peas were reported by Karr et a l . , (1958) and Linck (1961). Linck tent a t i v e l y concluded from an anatomical study of the problem, that lack of f e r t i l i z a t i o n was not the cause of embryo f a i l u r e . Other investigators have reported reductions i n pod f i l l due to low s o i l moisture (Bartz, 1959; Salter, 1963), mineral d e f i c i e n c i e s (Klacan and Berger, 1963), high s o i l tempera-tures (Klacan, 1962) and high a i r temperatures (Went, 1957; Lambert and Linck, 1958; Karr et a l . , 1958). It i s quite possible that, i n the present experiments, where roots were confined i n a r e l a t i v e l y small volume of s o i l , mineral de f i c i e n c i e s and\/or lack of a s o i l \/ a i r temperature d i f f e r e n t i a l may have masked possible e f f e c t s of temperature on peas per pod. 67. The data from experiments i n which day temperature was i n -creased at various stages of plant development indicate that the number of peas per pod was reduced by high temperature treatment (85\u00b0F) applied p r i o r to the f u l l bloom stage. This result does not agree with experiments reported i n the l i t e r a t u r e i n which i t was found that maximum s e n s i t i v i t y to high temperature occurred from f i v e to ten days a f t e r f u l l bloom (Lambert and Linck, 1958; Karr et a l . , 1958). The data of Lambert and Linck, however, i n -dicated that 90\u00b0F was more e f f e c t i v e than 85\u00b0F i n reducing pea y i e l d . It would be of considerable interest to repeat the present experiments using a more optimal temperature regime f o r the stan-dard environment and a high temperature treatment of 90\u00b0F. Pod pairs per plant were also reduced by a high temperature treatment applied p r i o r to flowering. When a high temperature (85\u00b0F) was imposed from the s i x t h node to maturity, (Experiment 8), the reduction i n pod pairs was the main cause of the decrease i n pea y i e l d . However, when a high temperature (90\u00b0F) was f o l -lowed by a lower temperature (70\u00b0F) from the thirteenth node to maturity (Experiment 10), i t was found that pea y i e l d was i n f l u -enced more by peas per pod than by pods per plant. In the l a t t e r experiment, the reduction i n pod pairs was compensated f o r by an increase i n the number of nodes which formed pods. The data indicate that there were y i e l d differences among plants grown at the same temperature i n d i f f e r e n t experiments. Yields were generally greater i n Experiment 2, f o r example, than i n Experiment 1. This was probably due to the fact that the sub-i r r i g a t i o n system of watering used i n the f i r s t experiment proved to be inadequate f o r supplying the plants' needs as was indicated by w i l t i n g of leaves and abscission of flowers (indicating the 68. importance of s o i l moisture i n a f f e c t i n g pea yield.),. However, the r e l a t i v e response to temperature i n repeated experiments was generally the same. The choice of the 5% l e v e l of significance f o r the presenta-t i o n of r e s u l t s , high v a r i a b i l i t y between repl i c a t e s and low num-ber of r e p l i c a t e s made i t d i f f i c u l t to demonstrate \" s i g n i f i c a n t \" differences. In some cases, treatment means were s i g n i f i c a n t at the 10 or 15$ l e v e l . This suggests that, i n small-sized experi-ments such as the present investigation, the use of a di f f e r e n t l e v e l of significance, perhaps 15$, would be more r e a l i s t i c . It would have been more desirable, however, to have a larger number of r e p l i c a t i o n s i n these experiments, but t h i s was prevented l a r g e l y by l i m i t a t i o n s of space and time. It should be emphasized that the re s u l t s obtained i n these experiments cannot be expected to exactly correspond with the tem-perature response pattern of peas grown under f i e l d conditions; nor can the response of Dark Skin Perfection peas be expected to correspond with that of a l l other v a r i e t i e s of peas. Under f i e l d conditions, temperature interacts with such environmental variables as l i g h t i n t e n s i t y , s o i l moisture, photoperiod and s o i l f e r t i l i t y , a l l of which were held constant i n the present experiments. Other factors to consider i n r e l a t i n g these r e s u l t s to response i n the f i e l d include the l i m i t a t i o n s on root growth i n pots, lack of a d i f f e r e n t i a l between s o i l and a i r temperatures and suddenness of diurnal temperature changes which obtained i n these experiments conducted i n controlled-environment cabinets. Despite these d i f -ferences between controlled-environment and f i e l d conditions, however, the r e s u l t s obtained here should be useful i n int e r p r e t -ing pea growth and development i n the f i e l d . s 69. SUMMARY Eff e c t s of temperature regimes ranging from 45\/50 to 90 \/75\u00b0F day\/night temperatures on the growth and development of Dark Skin Perfection peas were studied i n controlled-environment cabinets. Temperature was shown to influence f r u i t and vine y i e l d , rates of stem elongation and node development, position of the f i r s t flower and t i l l e r i n g . The rate of plant development up to the 15th node stage i n terms of nodes produced per day, increased steadily as tempera-ture increased. The rate was approximately proportional to the average temperature, in d i c a t i n g that night temperature was as ef f e c t i v e as day temperature. The number of days to a p a r t i c u l a r node stage decreased with increasing temperature and was a r e f l e c t i o n of the rates of germ-ination and node development. Number of days to maturity decreased as temperature increased, but was influenced by number of nodes to the f i r s t flower. High day-plus high night-temperature t r e a t -ments resulted i n an increase i n the number of nodes to the f i r s t flower and a delay i n the time to maturity. The number of nodes to the f i r s t flower was decreased at very low temperatures. Plant height decreased at temperatures above and below 60\/50\u00b0F. Plant height was increased at high day-plus high night-tempera-ture regimes as a secondary effect of an increase i n the number of nodes to the f i r s t flower. Rate of stem elongation was highest at 70 \/55\u00b0F and declined sharply at temperatures above 80\/60\u00b0F and below 60\/50\u00b0F. Vine y i e l d at a p a r t i c u l a r growth stage decreased as tempera-ture increased above 45\/40\u00b0F. 70. T i l l e r i n g was most p r o l i f i c .at the lower temperatures and was absent at a d ay temperature of 90\u00b0F. On a dry matter accumulation per day basis, vine growth decreased above and below a temperature optimum which shifted from 70\/60 to 60\/50\u00b0F i n the course of plant development. The rate of dry matter accumulation i n the stem declined with the onset of f r u i t development. Percent dry matter of plants was markedly increased at 45\/40\u00b0E Pea y i e l d decreased as temperature increased above 60\/50\u00b0F, due mainly to a reduction i n the number of pods per plant. The number of peas per pod was decreased at high day-plus high night-temperature and by high day-temperature treatments imposed p r i o r to f u l l bloom. 71. LITERATURE CITED Al'tergot, T.F. 1963. The ef f e c t of increased temperature on plants. Izv. Akad. Nauk SSSR, Ser. b i o l . 28: 57-73 (Hort. Abstr. 33: No. 4263). Barber, H.N. 1959. Physiological genetics of Pisum. I I . The genetics of photoperiodism and vernalization. Heredity 13: 33-60. Bartz, J.F, 1959. Y i e l d and ovule development of Alaska peas as i n f l u -enced by n u t r i t i o n and s o i l moisture. Ph.D. Thesis, University of Wisconsin. Beattie, W.R., L.L. Barter and B.L. Wade. 1942. Growing peas f o r canning and freezing. U.S. Dept. Agr. Farmers' Bui. 1920. Bonner, J . 1957. 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A Study of Phytometeorological E f f e c t s on the Growth and Development of Peas. Dept. of Meteorol., Univ-e r s i t y of Wisconsin, 165 PP. Warnock, S.J. and D.J. Hagedorn. 1954. Stigma r e c e p t i v i t y i n peas. Agron. Jour. 46: 274-277. Went, F.W. 1950. The response of plants to climate. Science 112:, 489-494. Went, P.W. 1957. The Experimental Control of Plant Growth. Chronica Botanica Company, Waltham, Mass. 343 pp. ","attrs":{"lang":"en","ns":"http:\/\/www.w3.org\/2009\/08\/skos-reference\/skos.html#note","classmap":"oc:AnnotationContainer"},"iri":"http:\/\/www.w3.org\/2009\/08\/skos-reference\/skos.html#note","explain":"Simple Knowledge Organisation System; Notes are used to provide information relating to SKOS concepts. 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