influence of temperature and photoperiod on growth and yield components in oats ( ...
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Influence of temperature and photoperiod on growth and yield components in oats (Avena sativa)
Plnr~r Scierlce Depcrrrrner~r, McGiII Ur~il~ersiry, Moctlor~crlcl College, Qile., Cnrlnckl
Received May 21, 1976
KLINCK, H. R. , and S . L . S I M . 1977. Influence of temperature and photoperiod on growth and yield components in oats (Al,er~o scrri~w). Can. J . Bot. 55: 9&106.
Two oat cultivars, Clintland 60 and Garry, were grown to maturity in controlled environments under two temperature regimes with daylength held constant and under two daylengths with a constant temperature pattern. Plants were moved between environments at panicle initiation and at anthesis. dividing the growth period into three phases.
Growth and development were hastened by warm temperature and by long days. Temperature treatments caused greater variation in the duration of growth phases in Garry than in Clintland 60, but Clintland 60 was affected more by daylength. Higher plant dry weights were obtained from cool temperature treatments; response to daylength was inconsistent.
Grain yield was not closely associated with duration of growth phases. The effect of tempera- ture and daylength on yield components was markedly different in the twocultivars. Thegreatest grain yield response in Clintland 60 resulted from cool temperature during panicle initiation to anthesis, attributable to increased fertile tiller development. Daylength had limited effect on components. In Garry the greatest yield response was from cool temperatures during anthesis to maturity, with increases in all components. Short days before anthesis increased grain size and number.
Implications of observed responses relative to cultivar performance in the field are discussed.
KLINCK, H. R.. et S . L. S I M . 1977. Influence of temperature and photoperiod on growth and yield components in oats (Atler~n scrtivcr). Can. J . Bot. 55: 9&106.
Les auteurs ont cultivk deux cultivars d'avoine, Clintland 60 et Garry. jusqu' i maturitk. dans des environnements contldles sous deux regimes de temperature, la longueur du jour etant constante. et sous deux longueurs dejour, le patron de temperature Ctant constant. Les plantsont ete changes d'environnements au moment d e ['initiation du panicule et B I'anthkse, divisant ainsi la p t ~ i o d e de croissance en trois phases.
La croissance et le developpement sont acceleres par la temperature chaude et par les jours longs. Les traitements de temperature entrainent plus de variations dans la duree des phases d e croissance chez Clintland 60. mais le Clintland 60 est plus sensible B la longueur du jour. Les t~ai tements B basse tempe~ature donnent les poids secs les plus ClevCs; la reaction Bla longueur du jour est incohkrente.
Le rendement en grain n'est pas etroitement associk avec la duree des phases de croissance. L'effet de la t empe~ature et de la longueur du jour sur les composantes du rendement d i re re nettement chez les deux cultivars. L e plus fort rendement en grain chez le Clintland 60 s'obtient avec une temperature fraiche pendant I'initiation du panicule jusqu'a I'anthkse, ce qui est at t~ibuable B une augmentation du developpement des talles fel-tiles. La longueur du jour exerce des effets limites sur les constituants. Chez le cultivar Garry, le plus haut rendement s'obtient avec des temperaturesfraiches pendant I'anthkse jusqu'amaturitC avec une augmentation d e tous les constituants. Des jours courts avant l'anthese augmentent la grosseur des grains e t leur nombre.
Les auteurs discutent les implications des comportements observes en relation avec la pelfor- mance des cultivars aux champs.
[Traduit par le journal]
Introduction (1974) indicate that considerable work has been
Variations in temperature and photoperiod done to determine the responses of wheat
bring about changes in the phasic development (Triticum aestivum L.) and barley (Hordeum and growth of and consequently affect Vulgare L.) cultivars to and day- their yield. Reviews by Kirby (,]969) and Thorne length. In an where spring wheat
plants were moved to different controlled en- 'Present address: AgricuItural Research Centre, De- vironments at spikelet initiation and anthesis,
partment of Agriculture, Sarawak, Malaysia. Thorne et al. (1968) found that grain yield was
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KLINCK AND SIM 97
affected by environmental differences in all growth periods. Cool conditions increased yield, while short-day treatments after spikelet initia- tion decreased it, as a result of differential effects on yield components. Guitard (1960) reported that the duration of specific growth phases and the number of fertile tillers in spring barley were influenced by both temperature and daylength.
Numerous attempts have been made to relate the growth responses of oats (Avena sativa L.) to naturally occurring temperatures, and the responses have differed depending on the loca- tion and the season. Hence, Coffman and Frev (1961) regarded oats as a crop requiring cool temperatures during germination and the period of vegetative growth, while Bretschneider- Herrmann (1966) found that a high grain yield in oats depended on a warm temperature before anthesis, followed by cool weather up to milk ripeness and warm weather in the final stages of ripening. Temperatures were expressed as being 'cool' or 'warm' only in relation to monthly or seasonal averages. Coffman and Frey (1961) noted also that an increase in daylength tends to hasten flowering in oats. Detailed studies of the effects of temperature and daylength on development and growth in oats under controlled environments seldom have been reported. Peterson and Schrader (1974) examined the influence of temperature on growth in oats, but only to the panicle emergence stage.
In much of the work reported in the literature insufficient attention has been given to cultivar differences. Space limitations inherent in the use of controlled-environment facilities for physio- logical studies frequently prevent investigating more than one or two cultivars at a time. If the results from a limited number of cultivars are interpreted as being representative of the species, contradictions are likely to exist. Wall and Cartwright (1974) observed considerable differ- ences among cultivars of spring wheat in their responses to temperature and photoperiod. Halse and Weir (1974) noted marked variation between cultivars in the effect of temperature on spikelet number in wheat. Cultivar differences in tillering and rate of leaf dry weight increase in response to temperature were reported for oats by Peter- son and Schrader (1974).
According to Kirby (1969) there is no general hypothesis about the effects of daylength on tillering, dry weight growth, or leaf production in cereals because contradictory results have been
obtained in different experiments. This points out the need for additional investigations on cultivar response.
The present paper reports on work designed to determine the influence of temperature and photoperiod on growth and yield components in specific cultivars of oats.
Materials and Methods An early maturing oat cultivar, Clintland 60, and a
medium maturing cultivar, Garry, were used in this study. Three growth cabinets were programmed to provide the following environments: warm, long days, 18 h light at 21 "C and 6 h darkness at 15 "C; cool, long days, 18 h light at 15 "C and 6 h darkness at 10°C; warm, short days, 13 h light at 21 "C and 11 h darkness at 15 "C. Light was supplied by panels of cool-white fluorescent tubes, supplemented with incandescent lamps, providing a mean intensity of 3.24 x lo4 lx. Relative humidity was adjusted to 70%.
Seeds of uniform size were sown in a plastic tray of perlite moistened with tap water and germinated in the dark at room temperature. Healthy seedlings, about 4 cm in length, were transplanted to round plastic pots, 10 cm in diameter, filled with a mixture of two parts loamy soil to one part perlite. The pots were placed close together in the cabinets so that the aerial portion of each plant had access to an area of 100 cm-2 in which to develop. A concentration of 5 x lo3 ppm of commercial plant nutrient 20-20-20 was applied at 5-day intervals.
The growth period was divided into three phases based on development of the main culm: (1) seeding to initiation of panicle development, (2) initiation of panicle develop- ment to anthesis of the apical spikelet, and (3) anthesis to maturity. At the end of each phase certain plants were shifted from one environment to another, some were removed for dry weight determinations, and others continued in the same environment. At maturity plants were available for study that had been grown under each of 15 different environments. In analysing the results no attempt was made to compare plants exposed to warm, short-day conditions with those exposed to cool, long-day conditions because of the difficulties of interpreting results from a mixture of temperature and daylength effects. Similarly, while results comparing daylength treatments have been included, it is recognized that the photoperiod treatments were confounded with light energy received. Therefore, the responses ascribed to photoperiod may be, in part, due to differences in light energy. Comparisons were made among eight groups of plants that had been exposed to long days throughout their life cycle but to different temperature patterns during different growth phases (W = warm vs. C = cool), and among eight groups of plants that had been exposed continuously to warm temperatures but to different daylengths (S = short days vs. L = long days). Thus, for example, plant W1C2C3 (see tables) was grown under cool conditions during growth phases 2 and 3, always warm conditions during growth phase 1 and under long days, while plant L,S2S3 was grown under long days in phase 1 and short days during phases 2 and 3, always at the warmer tem- perat ures.
Each of the four replications per treatment was com-
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CAN. J. BOT. VOL. 55. 1977
K E Y :
FIG. 1 . Effect of temperature on the number of days required by two oat cultivars to reach three stages of growth and development. I bars indicate significance a1 P = 0.05.
prised of two plants. The end of growth phase 1 (initia- tion of panicle development) was determined by dissecting and examining the apices of the main culm of spare planls.
Results
Dlo.atiot1 of Gron,th Pllases Warm temperature shortened each growth
phase irrespective of the previous environment or the cultivar (Fig. 1). When phase 1 was warm, both cultivars reached initiation of panicle development 6 to 8 days earlier than when phase 1 was cool. A warm phase 2 brought about anthesis 23 to 26 days after panicle initiation, regardless of temperature during phase 1 . Cool conditions in phase 2 delayed anthesis and Garry was affected more than Clintland 60. Warin conditions in phase 3 enhanced maturity in both cultivars, more markedly where phase 2 had been cool. Cool conditions in phase 3 delayed maturity more where phase 2 had been warm. Garry generally developed faster than Clintland 60 in phase 3 where phase 1 had been warm, regardless of temperature in phase 2. Where phase 1 had been cool the response of the
two cultivars in phase 3 was either similar or Clintland 60 developed faster. Under continuous warm conditions Clintland 60 completed its life cycle in 79 days, or 23 days earlier than under continuous cool conditions. Garry was 7 days later than Clintland 60 under warm environ- ments but 22 days later under continuous cool conditions.
Long days hastened growth and development and shortened the duration of each growth phase irrespective of the previous environment o r the cultivar (Fig. 2). Within a given daylength treatment both cultivars required about the same nunlber of days during phase 2 to reach anthesis. In phase 3 Garry required fewer days to reach maturity than did Clintland 60 wherever material had been exposed to long days in phase 1, irrespective of daylength in phase 2. Where material had been exposed to short days in phase 1, however, the cultivar response in phase 3 was the reverse, Clintland 60 maturing in fewer days after anthesis than Garry. Under continuous long-day conditions Clintland 60 con~pleted its life cycle 3 weeks earlier than
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K E Y : I 5.0.. D A Y S 0 LONG D A Y S
FIG. 2. EfTect of daylength on the nun~ber of days required by two oat cultivars to reach three stages of growth and developn~ent. I bars indicate significance at P = 0.05.
under short days. Garry was I week later than temperature treatment. During phase 3, however, Clintland 60 under long days but 3 weeks later Garry accumulated significantly more weight under the continuous short-day environment. than did Clintland 60 under all temperatures,
The range in maturity dates brought about by and the differences were greater under cool temperature and daylength treatments was only conditions. In all cases the effects of cool 23 days in Clintland 60 compared with 38 days temperature were cumulative so that in phase 3 in Garry. The range in days required to complete growth phase 1 was only slightly greater in Garry than in Clintland 60 and was greater for daylength treatments than for temperature treat- ments (Fig. 3). However, the differences between the cultivars widened during phases 2 and 3. Garry was influenced more than Clintland 60 by temperature during all growth phases, while Clintland 60 was affected more than Garry by daylength after the panicle initiation stage. The major influence of daylength on rate of develop- ment occurred during phase 2 ; temperature had the greatest effect during phase 3.
Pk~tlr D I ~ Weight Higher plant dry weights were obtained a t the
end of every phase under cool conditions (Fig.
higher weights were obtained from plants that had been exposed to cool temperatures during phase 2, and in general, higher weights at ma- turity were obtained from plants that had been exposed to cool temperature during phase I . The largest total plant weights, then, were obtained from plants grown under cool condi- tions throughout, Garry being about 63% heavier than Clintland 60, and the smallest weights were obtained from plants grown con- tinuously a t the higher temperature, with a cultivar difference of only 9%.
Daylength had limited effect on dry weight production in Clintland 60 (Fig. 5). In Garry significantly higher weights were obtained under short days in phase 1. In phase2 weights obtained fro111 plants exposed to long days appeared to be
4). The cumulative dry weights to anthesis were higher, but differences were not significant. In similar for the two cultivars within a given phase 3 the response to daylength varied with
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100 CAN. J . BOT. VOL. 55, 1977
G R O W T H P H A S E
FIG. 3. Development responses of two oat cultivars to temperature and daylength treatments during specific growth phases. Clintland 60, temperature; . Garry, temperature; 0 Clintland 60, daylength; Garry, daylength.
previous treatment. Weight increments were higher where plants had been exposed to short days in phase 2, but differences resulting from different daylength exposures in phase 1 were inconsistent.
Plant dry weight increments varied over a wider range in Garry than in Clintland 60 during phase 3 under both temperature and daylength treatments. Temperature treatments caused greater variation than daylength treat- ments.
N~imber of Panicles Data in Table 1 indicate the number of tillers
bearing emerged panicles at anthesis and fertile panicles at maturity in each cultivar. Poorly developed panicles failed to set seed under certain environments, and in other conditions new panicles emerged and produced grain during phase 3. More panicles had been pro- duced under cool than under warm conditions by anthesis. Exposure to warm temperatures during phases 1 and 2 increased the number of fertile panicles at maturity in Garry. Warm temperature in phase 3 was less favourable to fertile panicle development. Conditions most detrimental to panicle survival in both cultivars were warm temperatures during phase 3 following cool temperatures in phases 1 and 2.
By the end of phase 2 (anthesis), more panicles
had been produced by plants exposed to short days during phase 1 than by those grown under long days, but the differences disappeared by the time maturity was reached (Table I). In plants of Garry grown under short days in phase 1, about half of the panicles present at anthesis failed to set seed. In plants that had been grown under long days during phase 1, all panicles present at anthesis in Garry set seed, and additional panicles emerged during phase 3. Daylength during phase 2 had no effect on panicle develop- ment. The influence of daylength on panicle survival in Clintland 60 was minimal. More panicles were produced by Garry than by Clint- land 60 under all temperature and daylength treatments.
Yield and Yield Components Highest grain yields were obtained from
plants maintained at a cool temperature through- out their life cycle (Fig. 6). Slightly lower yields occurred where plants had been exposed to warm conditions up to the time of panicle initiation and then to cool temperatures. Con- stantly warm temperatures were detrimental to yield.
In Clintland 60, cool temperatures during phase 1 had only minor effects on grain yield (Fig. 6) but significantly reduced the number of grains per panicle and increased the number of panicles per plant (Table 2). In Garry, cool conditions during phase 1 generally brought about a higher grain yield. This was due to a significantly larger number of grains per panicle, which more than compensated for reductions in grain size and panicle number. Both cultivars produced higher grain yields after exposure to cool temperatures during phases 2 and 3. Yield increases in Clintland 60 were due to larger panicle numbers, which offset the significant reduction in grains per panicle. In Garry, yield increases from phase 2 treatment were due to increases in number of grains per panicle and grain size, and increases from phase 3 treatment were due to increases in all yield components. The response of Garry to cool temperature in grain size and number was considerably greater than that of Clintland 60, but Clintland 60 responded more vigorously in panicle produc- tion (Table 2).
Daylength generally had less effect on grain yield than did temperature. In Clintland 60, the effect of daylength treatments on grain yield was
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TABLE I . Effect of temperature and daylength on yield components in Clintland 60 and Garry oats grown under different environments
No. panicles No. panicles No. grains Weight per at anthesis at maturity per plant grain (mg)
Environment C1.60* Carry C1.60 Carry C1.60 Garry C1.60 Carry
Warm (W) vs. cool (C) WlW2W3 7 12 WlW2C3 7 12 w1czw3 9 14 w1czc3 9 14 C I W Z W ~ 8 9 c1wzc3 8 9 c1czw3 11 15 c1czc3 11 15
Short days (S) vs. long days (L) SISZS, 8 17 s1szL3 8 17 SILZS, 6 14 S I L Z L ~ 6 14 LLS2S3 5 10 LlS2L3 5 10 LlL2S3 7 12 LlL2L3 7 12
SET 0.5 0.8
"Clintland 60. ?Standard error.
relatively small, but short days during phase 1 increased yield slightly (Fig. 7), resulting from an increased number of panicles (Table 2). An increase in the number of grains per panicle brought about yield increases under short-day treatments in phase 2. In Garry, yield was increased by exposure to short days during phase 1 or during phase 2, as a result of significant increases in the number of grains per panicle and in spite of a reduction in the number of panicles. Daylength effects during phase 3 on grain yield were small and inconsistent.
Discussion
In considering the results of these investiga- tions it is necessary to recognize that the re- sponses to daylength treatments may reflect, in part, differences in the amount of light energy received by the plants. During each 24-h period the plants exposed to long days received light for 5 h more than the plants grown under short days, and during this time they were also held at the 5 "C higher daytime temperature. Thus, it was not possible to separate the responses resulting from photoperiod from those induced by light energy differences, and in the discussion they are referred to only as daylength effects.
Growth and development were generally hastened by warm temperatures and by long days. The two cultivars, Clintland 60 and Garry, responded quite differently to the controlled- environment conditions to which they were exposed. Under continuous warm long days Garry matured about 1 week later than Clintland 60. Under continuous cool days, and in environ- ments involving early and prolonged exposure to cool temperature or short days, Garry matured 3 or 4 weeks later than Clintland 60. The relative response of the two cultivars to temperature and daylength treatments may be a reflection of differences in their genetic back- ground. Clintland 60, selected in Indiana, U.S.A., was derived in part from common oats (Avena sativa L.) but contains as one parent the red oat cultivar Landhafer (Avena byzantina C. Koch). Garry, selected in Manitoba, Canada, was derived mainly from common oat parentage. According to Coffman and Frey (1961), red oats are more heat tolerant than common oats. This may explain why Clintland 60 was influenced less than Garry by temperature in the present investigations.
Earlier heading and maturity of Garry oats grown at 18.5 compared with 13.5 "C was re-
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E N V I R O N M E N T
FIG. 6. Effect of temperature during different growth phases on grain yield of two oat cultivars. I bars indicate significance at P = 0.05.
TABLE 2. Mean percentage increases in grain yield and yield components in Clintland 60 and Garry oats attributable to exposure to cool temperature or to short daylengths during specific growth phases
Clintland 60 Carry -
Phase Phase Phase Phase Phase Phase 1 2 3 1 2 3
Grain yield No. grains per panicle Weight per grain No. panicles per plant
Grain yield No. grains per panicle Weight per grain No. panicles per plant
Cool temperature 42 24 - 5 - 17
6 6 42 43
Short daylength 16 -4 8 - 5 4 1 0 0
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0 G A R R I
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FIG. 7. Effect of daylength during different growth phases on grain yield of two oat cultivars. I bars indicate significance at P = 0.05.
ported by Fulton (1968). Guitard (1960) noted that increasing the photoperiod and the tempera- ture reduced the duration of different growth phases in spring barley. Marcellos and Single (1971) observed that the length of periods from seeding to ear initiation a n d from ear initiation to flowering in spring wheat were highly corre- lated with temperature and photoperiod. Wall and Cartwright (1974) also reported that long days decreased the time to heading in spring wheat, but the degree to which this effect was noted depended on previous treatment. Thorne et al. (1968) noted that either low temperature or short days lengthened the growth phases in spring wheat. Marcellos and Single (1972) showed that air temperature was the principal factor influencing the rate of development during the postanthesis phase; the influence of photo- period was not significant.
Both Thorne et al. (1968) and Guitard (1960) observed that phase 3 was shortened by exposure to short days in phase 1. Similar results were obtained with Clintland 60 in the present work, but in Garry such treatments during phase 1 prolonged the duration of phase 3.
Dry weight production was always higher under cool conditions. This could be accounted for by the increased production of tillers from cool temperature treatments during phases 1 and 2. Similar results were reported for spring wheat by Thorne et al. (1968) and for oats by Peterson and Schrader (1974). In phase 3, however, there
was little relationship between dry weight and tiller number at a given temperature in Garry because more fertile panicles were present at maturity where temperatures before anthesis had been warm. Such a trend did not occur with Clintland 60.
Daylength effects on dry weight production in Clintland 60 were minimal; the greater re- sponses noted in Garry depended on previous treatment and were not closely related to tiller production. While short days have been reported to increase the number of ears in cereals (Kirby 1969), Guitard (1960) observed more fertile tillers in barley exposed to long days during phases 2 and 3. In these investigations short days before panicle initiation increased the number of panicles, but in Garry many of the panicles were sterile. Long-day treatment during phase 1, while producing fewer panicles, resulted in a larger number of fertile panicles at maturity. Long-day treatment during phases 2 and 3 slightly increased fertile panicle number in Garry but had no effect on Clintland 60.
The increased grain yield obtained from exposure of plants to cool temperature in the present work is in agreement with results re- ported by other workers for oats (Fulton 1968) and spring wheat (Thorne et al. 1968; Thorne 1974). Responses of the yield components in oats varied with the cultivar and were not always similar to those reported for spring wheat.
Environmental differences in all three growth
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KLINCK AND SIM 105
phases affected grain yield. In terms of response to temperature the most important phase in Garry was the period between anthesis and maturity. According to Thorne (1974), photo- synthesis is affected negligibly over the tempera- ture range of 10 to 20°C. Therefore, yield variations resulting from different temperature treatments can be explained by the effect of temperature on tillering, expansion of photo- synthetic organs, and duration of photosynthetic activity. The longer duration of phase 3 a t the cooler temperature can account partially for the higher grain yield obtained. Wardlaw (1970) found that high temperature applied to spring wheat plants after anthesis reduced yield. Temperature treatments applied during 10 days after anthesis reduced seed set, while later treatment reduced seed size. In this work the higher temperature during phase 3 significantly reduced grain size and numbers in Garry. In Clintland 60 the most important growth phase was the period between panicle initiation and anthesis. Temperature during this period affected only the tillering component of yield.
Response to daylength treatments revealed that the most important period for both cultivars was phase 2. Thorne et al. (1968) reported a yield decrease of 24% in spring wheat from exposure
- ~
to short days during phase 2, but in the present work short-day treatments increased yield by 16% in Clintland 60 and 63% in Garry. Shorten- ing of the preheading phase in spring wheat has been reported t o result in fewer grains per ear (Wall and Cartwright 1974). In the present work, where anthesis occurred earlier as a result of higher temperature or longer days, the number of grains per panicle in Garry was significantly reduced, while in Clintland 60 the effects were minimal. Individual grain weights were un- affected by daylength in either cultivar. Kirby (1969) also observed that 1000-grain weights in cereal have shown no consistent response to daylength treatments in either pot o r field experiments.
This study has demonstrated the marked variation that can occur between oat cultivars in the effects of temperature and daylength on growth and development and on the components of grain yield. The responses observed under controlled environments may help to explain differences in the performance of these cultivars in the field. When deve!opment is expressed as the duration of specific growth phases, Garry is shown t o be more responsive than Clintland
60 to temperature variations, but Clintland 60 was affected inore by daylength. Yield response, however, was not closely associated with de- velopment. Measured by the range in grain yields, Garry responded more than Clintland 60 to both temperature and daylength variations. It appears that Garry will suffer more than Clintland 60 from exposure to higher tempera- tures, particularly during the grain-filling period. High temperature affects all yield components in Garry, interfering not only with grain filling but also with floret fertility and panicle de- velopment. Clintland 60 produces fewer fertile panicles under warm temperatures, but floret fertility is relatively high and grain filling is not significantly impaired. Thus, one would expect Clintland 60 t o have a more southerly adaptation than Garry in the spring oat growing areas of North America. While short days during the preanthesis phase enhance grain yield in these cultivars, daylength during the grain-filling period is not an important factor.
Comparative dates of seeding data for the two cultivars are not readily available. Nass et al. (1974) have shown that grain yield in Garry oats is reduced significantly by delayed spring seeding, resulting in part from smaller grain size. Evidence from the present work suggests that for the highest yields, cultivars such as Garry should be seeded early in the spring to take advantage of short days before anthesis and cool tempera- ture during the grain-filling period. seedinidate may not be as critical for maintaining yield levels in cultivars having environmental response characteristics similar to those of Clintland 60.
Acknowledgement Grateful acknowledgement is extended to the
National Research Council of Canada for financial assistance in support of this project.
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