Effects of Temperature, Photoperiod and Seed Vernalization on Flowering in Faba Bean Vicia faba

Factorial combinations of three photoperiods (10, 13 and 16h), two day temperatures (18 and 28 °C) and two night temperatures(5 and 13 °C) were imposed on nodulated plants of six diversegenotypes of faba bean (Vicia faba L.). Plants were grown inpots in growth cabinets from both vernalized (1.5±0.5°C for 30 d) and non-vernalized seeds. The times from sowingto the appearance of first open flowers (f) were recorded. Seedvernalization decreased the subsequent time taken to flowerin almost all genotype x growing environment combinations (theexceptions were plants of the cv. Maris Bead grown in threecooler, short-day regimes). The influence of temperature andphotoperiod on the rate of flowering was quantified, using amodel applied previously to other long-day species of grainlegume in which positive linear relations between both temperatureand photoperiod and the rate of progress towards flowering areassumed to apply. A significant positive linear response ofrate of progress towards flowering to limited ranges of meandiurnal temperature was detected in all six genotypes, but inthree genotypes (Syrian Local Large, Aquadulce and Maris Bead)the 28 °C day temperature reduced the rate of progress towardsflowering - suggesting that the optimum temperature for floweringin these genotypes is below 28 °C. In four genotypes (MarisBead, Giza-4, Aquadulce and BPL 1722) a significant positiveresponse to photoperiod, typical of quantitative long-day plants,was observed only in plants grown from vernalized seeds. Incontrast, plants of the genotype Zeidab Local grown from bothnon-vernalized and vernalized seeds showed the same positiveresponse to photoperiod, whereas plants of the land-race SyrianLocal Large were consistently unresponsive to photoperiod. Theimplications of this range of responses amongst diverse genotypesare discussed in relation to screening germplasm. Vicia faba, faba bean, flowering, photoperiod, temperature, seed vernalization, germplasm screening     

The Effects of Temperature, Photoperiod and Light Integral on the Time to Flowering of Pansy cv. Universal Violet (ViolaxwittrockianaGams.)

The effects of temperature, photoperiod and light integral onthe time to first flowering of pansy (ViolaxwittrockianaGams)were investigated. Plants were grown at six temperatures (meansbetween 14.8 and 26.1 °C), combined with four photoperiods(8, 11, 14 and 17 h). The rate of progress to flowering increasedlinearly with temperature (up to an optimum of 21.7 °C)and with increase in photoperiod (r²=0.91, 19 d.f.), the latterindicating that pansies are quantitative long day plants (LDPs).In a second experiment, plants were sown on five dates betweenJuly and December 1992 and grown in glasshouse compartmentsunder natural day lengths at six temperatures (means between9.4 and 26.3 °C). The optimum temperature for time to floweringdecreased linearly (from 21.3 °C) with declining light integralfrom 3.4 MJ m^-2d^-1(total solar radiation). Data from both experimentswere used to construct a photo-thermal model of flowering inpansy. This assumed that the rate of progress to flowering increasedas an additive linear function of light integral, temperatureand photoperiod. Independent data from plants sown on threedates, and grown at five temperatures (means between 9.8 and23.6 °C) were used to validate this model which gave a goodfit to the data (r²=0.88, 15 d.f.). Possible confounding ofthe effects of photoperiod and light integral are discussed. Pansy;Violaxwittrockiana; flowering; photo-thermal model; temperature; photoperiod; light integral     

Photothermal Responses of Flowering in Rice (Oryza sativa)

Durations from sowing to panicle emergence in 16 diverse genotypesof rice (Oryza sativa L.) were recorded in 13 different photothermalregimes, comprising constant and diurnally alternating temperaturesbetween 16 and 32 °C and photoperiods between 10.5 and 15.0h d^–1—all provided by controlled-environment growthcabinets. In 11.5 h days and at sub-optimal temperatures, relationsbetween the rate of progress towards panicle emergence and meantemperature were linear in all genotypes, and amongst thesethe base temperature at that photoperiod varied between 6.6and 11.9 °C. In most cases progress was most rapid at 24–26°C, i.e. the optimum temperature was much cooler than expectedfrom previously published values of times to panicle emergencein a less extensive range of photothermal regimes. Only in threecultivars was it warmer than 28 °C, and in these there weresufficient data to establish that relations between rates ofprogress to panicle emergence and photoperiod in the diurnallyalternating temperature regime of 28–20 °C are alsolinear. Also, the responses of these three cultivars provideno evidence of any interaction between the effects of photoperiodand temperature. We conclude, then, that the model in whichrate of development is a linear function of both temperatureand photoperiod with no interaction, which has been shown tobe common to many other species, also applies to rice. Differencesamong genotypes in relative sensitivity of rate of progresstowards panicle emergence to both temperature and to photoperiodwere considerable; japonica cultivars tended to be more sensitiveto temperature and less sensitive to photoperiod than indicacultivars. Four indica cultivars bred and selected at The InternationalRice Research Institute (IRRI) in the Philippines did not differ(P > 0.10) in their relations between rate of progress towardspanicle emergence and sub-optimal temperatures in a daylengthof 11.5 h, but the optimum temperature for cv. IR 36 was appreciablywarmer than that for the cvs IR 5, IR 8 and IR 42. Oryza sativa, rice, flowering, temperature, photoperiod, photothermal responses     

Effects of Temperature and Photoperiod on Flowering in Soya bean [Glycine max (L.) Merrill]: a Quantitative Model

Factorial combinations of five photoperiods (8 h 20 min, 10h, 11 h 40 min, 13 h 20 min and 15 h) and three night temperatures(14, 19 and 24 C) combined with a single day temperature (30C) were imposed on nodulated plants of nine soya bean genotypes[Glycine max (L.) Merrill] grown in pots in growth cabinets.The times to first appearance of open flowers were recorded.For a photoperiod-insensitive cultivar, and for the remainingeight photoperiod-sensitive genotypes in photoperiods shorterthan the critical daylength, the rates of progress towards flowering(the reciprocals of the times taken to flower) were linear functionsof mean diurnal temperature. For all photoperiod-sensitive genotypes,times to flowering in photoperiods longer than the criticaldaylength increased as inverse functions of both increasingphotoperiod and decreasing temperature. A consequence of thesetwo relations is that the critical daylength becomes longerwith higher mean temperatures. In the five photoperiod-sensitivegenotypes which flowered in all environments before the experimentwas terminated (after 150 d) the delays in flowering due tolow temperatures or long photoperiods were limited by a maximumperiod to flowering specific for each genotype. These resultsare discussed in relation to the development of a simple techniquefor the large-scale screening of soya bean germplasm to determinephoto-thermal response surfaces for flowering. Glycine max (L.) Merrill, soya bean, flowering, photoperiod, temperature, screening, germplasm     

Effects of Temperature and Photoperiod on Phenological Development in Three Genotypes of Bambara Groundnut (Vigna subterranea)

Factorial combinations of four photoperiods (10, 11·33,12·66 and 16 h d^-1) and three mean diurnal temperatures(20·2, 24·1 and 28·1°C) were imposedon nodulated plants of three Nigerian bambara groundnut genotypes[Vigna subterranea (L.) Verdc., syn. Voandzeia subterranea (L.)Thouars] grown in glasshouses in The Netherlands. The photothermalresponse of the onset of flowering and the onset of poddingwere determined. The time from sowing to first flower (f) wasdetermined by noting the day on which the first open flowerappeared. The time from sowing to the onset of podding (p) wasestimated from linear regressions of pod dry weight againsttime from sowing. Developmental rates were derived from thereciprocals of f and p. In two genotypes, 'Ankpa 2' and 'Yola',flowering occurred irrespective of photoperiod and 1/f was controlledby temperature only, occurring sooner at 28·1 than at20·2°C. The third genotype, 'Ankpa 4', was sensitiveto temperature and photoperiod and f was increased by coolertemperatures and photoperiods > 12·66 h d^-1 at 20·2°Cand > 11·33 h d^-1 at 24·1 and 28·1°C.In contrast, p was affected by temperature and photoperiod inall three genotypes. In bambara groundnut photoperiod-sensitivitytherefore increases between the onset of flowering and the onsetof podding. The most photoperiod-sensitive genotype with respectto p was 'Ankpa 4', followed by 'Yola' and 'Ankpa 2'. Therewas also variation in temperature-sensitivity between the genotypesinvestigated. Evaluation of bambara groundnut genotypes foradaptation to different photothermal environments will thereforerequire screening for flowering and podding responses.Copyright1994, 1999 Academic Press Vigna subterranea (L.) Verdc., Voandzeia subterranea (L.) Thouars, bambara groundnut, phenology, photoperiod, daylength, temperature, flowering, podding     

Rates of Progress towards Flowering and Podding in Bambara Groundnut (Vigna subterranea) as a Function of Temperature and Photoperiod

The influence of temperature and photoperiod on phenologicaldevelopment of three bambara groundnut (Vigna subterranea) selectionsfrom Botswana, Zimbabwe and Mali was investigated in a semi-controlledenvironment experiment with factorial combinations of threeconstant temperatures (20.9, 23.4 and 26.2 °C) and fourconstant photoperiods (10.0, 12.5, 13.5 and 16.0 h d^-1). Inall three selections, the onset of flowering was influencedby temperature but not by photoperiod, while the onset of pod-growth(‘podding’) of all three selections was influencedby both factors. The influence of temperature and photoperiodwas quantified by means of photothermal models, linking developmentrates to temperature and photoperiod with linear equations.The rate of progress from sowing to flowering of the three selectionscould be described very well (r²>95%) as a function of temperature;the rate of progress from flowering to podding was describedreasonably well as a function of both temperature and photoperiodby a combination of one to three response planes (r²for thedifferent selections ranging from 63 to 90%). Model testingwith independent data sets showed good agreement between observedand predicted times to flowering and podding. Vigna subterranea; Voandzeia subterranea; bambara groundnut; phenology; development; flowering; podding; photoperiod; temperature; modelling     

Day and Night Temperature Control of Floral Induction in Stylosanthes guianensis var. guianensis cv. Schofield

Floral initiation in seedlings of Stylosanthes guianensis var.guianensis cv. Schofield grown at a photoperiod marginal forflowering (12–11.75 h) was promoted by a combination oflow day (25 °C) and low night (16 or 21 °C) temperatures,and completely inhibited by a 35 °C day temperature. Additionally,earliness of floral initiation under naturally decreasing daylengthwas negatively related to temperature regime over the range35/30 to 20/15 °C (day/night). Stylosanthes guianensis var, guianensis, flowering, temperature, photoperiod, short-day plant     

Temperature and photoperiodic control of developmental responses in climatic races of Mimulus

Two strongly differentiated climatic races of the Mimulus cardinalis-lewisiicomplex were grown at a variety of temperatures (3–27°C)and photoperiods (8 and 16 hr) under controlled environmentalconditions. M. cardinalis (the lowland race, 400 m) and M. lewisii(the sub-alpine race, 3200 m) were found to differ in theirphysiological responses to the varied environments in severalsignificant ways: 1) At 27°C (16 hrphotoperiod), M. lewisiisustained 100% mortality in contrast to the substantial growthand flowering of M. cardinalis under these conditions; 2) In8 hr photoperiods at all temperatures, there was little growthand no flowering in M. lewisii whereas there was considerablegrowth at all temperatures, and flowering at 23 and 27°Cin M. cardinalis; 3) At low temperatures (7–15°C),16 hr photoperiods, flowering occurred a week or two earlierin M. lewisii than in M. cardinalis. The lowland race has asignificantly wider temperature and photoperiodic tolerancethan has the sub-alpine race. Applications of gibberellic acidto rosette Mimulus plants under non-inductive conditions (15°C,8 hr photoperiod) promoted vigorous stem elongation withoutflowering. The application of steroids, other hormones and metaboliteshad no observable effects. ¹Present address: Faculty of Botany, Ohio State University,Columbus, Ohio, U.S.A. (Received March 16, 1970; )     

Environmental Control of Flowering in some Northern Carex Species

The environmental control of flowering in some arctic-alpineCarexspecies has been studied in controlled environments.Carex nigra,C. brunnescens, C. atrata, C. norwegica andC. serotina all hada dual induction requirement for flowering. In all exceptC.nigra either low temperature (12 °C or lower) or short days(SD) over a wider range of temperatures were needed for primaryfloral induction and inflorescence formation. InC. nigra primaryfloral induction took place in SD only (9–21 °C),8–10 weeks of exposure being required for a full response.In all these species long days (LD) were required for, or stronglypromoted, culm elongation and inflorescence development (secondaryinduction). Quantitative ecotype differences in both primaryand secondary induction were demonstrated. Unlike the otherspecies,C. bicolor proved to be a regular LD plant which requiredLD only for inflorescence initiation and development. In allspecies leaf growth was strongly promoted by LD, especiallyin the higher temperature range (15–21 °C). In SDand temperatures below 15 °C the leaves became senescentand the plants entered a semi-dormant condition which was immediatelyreversed by LD. The results are discussed in relation to growthform and life history of shoots. Carex ; dual induction; ecotypic diversity; flowering; growth; photoperiod; sedges; temperature     

A Quantitative Model of Reproductive Development in Cowpea [Vigna unguiculata (L) Walp.] in relation to Photoperiod and Temperature, and Implications for Screening Germplasm

Factorial combinations of four photoperiods (10 h, 11 h 40 min,13 h 20 min and 15 h) and three night temperatures (14, 19 and24 °C) combined with a single day temperature (30 °C)were imposed on nodulated plants of 11 cowpea accessions [Vignaunguiculata (L) Walp.] grown in pots in growth cabinets. Thetimes to first appearance of flower buds, open flowers and maturepods were recorded. Linear relationships were established betweenthe reciprocal of the times taken to flower and both mean diurnaltemperature and photoperiod. When the equations describing thesetwo responses are solved, the time to flower in any given photothermalregime is predicted by whichever solution calls for the greaterdelay in flowering. Thus in different circumstances floweringis controlled exclusively by either mean temperature or photoperiod.The value of the critical photoperiod is temperature-dependentand a further equation, derived from the first two, predictsthis relationship. Considered together as a quantitative modelthese relationships suggest simple field methods for screeninggenotypes to determine photo-thermal response surfaces. Vigna unguiculata (L) Walp., cowpea, reproductive development, photoperiod, temperature, germplasm     

Dual Floral Induction Requirements in Phleum alpinum

Flowering requirements of four Norwegian populations of Phleumalpinum were studied in controlled environments. A dual inductionrequirement was demonstrated in all populations. Inflorescenceinitiation had an obligatory requirement for short days (SD)and/or low temperature, while culm elongation and heading wereenhanced by long days (LD) and higher temperatures. At 3 and6 °C primary induction was almost independent of photoperiod,whereas SD was more effective than LD at higher temperatures.The critical temperature for primary induction was about 15°C in SD and 12 °C in LD. Saturation of induction required12 weeks of exposure to inductive conditions, although someheading and flowering took place with 6 weeks exposure to optimalconditions (9 °C/SD). Inflorescence development also tookplace in 8 h SD although it was delayed and culm elongationwas strongly inhibited compared with LD conditions. Only smalldifferences in flowering response were found between the populations. Phleum alpinum L., alpine timothy, dual floral induction, flowering, photoperiod, temperature     

Developmental Responses to Temperature and Photoperiod in Ecotypes of Medicago polymorpha L. Collected Along an Environmental Gradient in Central Chile

The phenological development of nine Chilean accessions of Medicagopolymorpha, collected along a north–south aridity gradient,and of two commercial cultivars of the same species, were comparedin 12 sequential outdoor sowings at Cauquenes (35°58'S,72°17'W, elev. 177 m), in the sub-humid Mediterranean climatezone of Chile. A glasshouse experiment was also conducted toevaluate the effect of photoperiod on phenophase timing. Therewas a clear gradient in precocity among the Chilean accessionsin both experiments: accessions MPO-9-88 and MPO-7-88, fromthe arid zone, were the earliest-flowering accessions, whereasMPO-36-88 from the humid Mediterranean zone was the latest.Both experiments revealed significant variation among the Chileanaccessions in the response of flowering time to variation inphotoperiod regime. Differences in days to flowering betweenthe least- (8 h) and the most- (16 h) inductive photoperiodswere lower in precocious accessions from arid and semi-aridzones, than in late-flowering accessions from more humid zones.Rate of progress to flowering, defined as the inverse of timefrom emergence to first flower appearance (1/ f), was relatedto mean diurnal temperature, or to both mean diurnal temperatureand mean photoperiod. In two early-flowering accessions fromthe arid zone, and in the Australian cultivar ‘CircleValley’, 1/ f was affected significantly (P < 0.05)by both temperature and photoperiod. In the remaining accessions,no significant responses to temperatures were detected; 1/ fwas influenced significantly by photoperiod only. Copyright2000 Annals of Botany Company Annual medic, aridity gradient, Medicago polymorpha, flowering time, rate of development     

Photoperiod and Temperature Effects on Late Developmental Stages of Stylosanthes guianensis

Seedlings of Stylosanthes guianensis var. guianensis cv. Cookand S. guianensis var. pauciflora cv. Bandeirante were defoliatedand placed in a naturally lit glasshouse at 23/18 °C, 28/23°C or 33/28 °C (day/night). After exposure to 14 h daysand after floral induction with 30 cycles of 11 h, plants wereallocated to 11, 12, 13 or 14 h during flowering and seed formation. Floral initiation occurred after 10–15 short-day cycles.Flower appearance was hastened by warm temperatures and spikenumber per plant at 20 d after flower appearance was negativelyrelated to temperature and greater in Cook than in Bandeirante.Exposure to 13- and 14-h days reduced the continued differentiationof inflorescences in Bandeirante, and in Cook in warm temperatures.Floret number per spike was greatest at 23/18 °C and a higherproportion of florets aborted in Bandeirante at 33/ 28 °C.Variations in seed setting of the bi-articulate loment of Bandeiranteare described. Highest potential seed yield occurred if afterfloral induction 11 or 12 h days were maintained with 23/18°C or 28/23 °C temperatures. Photoperiod, temperature, development, Stylosanthes guianensis, flowering     

Modelling Temperature Effects in Breaking Rest in Red-osier Dogwood (Cornus sericea L.)

Temperature requirements for bud development after a rest period(breaking rest) from maximum rest to end of rest were determinedto develop an empirical model for predicting rest developmentin terminal vegetative buds of red-osier dogwood (Cornus sericeaL.). One-year-old plants at maximum rest were exposed to temperaturesfrom 5 to 20 °C a 12 h photoperiod (SD) in growth chambers.Depth of rest was measured by days to bud break in either 16h photoperiod (LD) or natural daylength at 20/15 °C/nighttemperature. Developmental stages during rest development wereexpressed by degree growth stage (°GS). Chilling was effective breaking rest after plants attained maximumrest (270 °GS). Development during rest (breaking rest)increased with decreasing temperature. No significant developmentoccurred at 20 °C. Rate of rest development (°GS h^–1)at all temperatures varied during the breaking rest period anddepended on developmental stage (°GS). A °GS model describedand quantified rest development (°GS). Using temperatureand developmental stage, the model predicted end of rest (315°GS)within 3 days and daily rest development (°GS) in both years. Cornus sericea L, Cornus stolonifera Michx, dogwood, bud development, dormancy, temperature effects, chilling, degree growth stage     

The Effects of Temperature and Light Integral on the Phases of Photoperiod Sensitivity inPetuniaxhybrida

Flowering in petunias is hastened by long days, but little isknown about when the plants are most sensitive to photoperiod,or how light integral or temperature affect such phases of sensitivity.The effects of these factors on time to flowering was investigatedusing reciprocal transfer experiments between long (16 h d^-1)and short days (8 h d^-1). The effect of light integral on thephases of photoperiod sensitivity was examined using two sowingdates and a shading treatment (53% transmission). The effectsof temperature were investigated by conducting reciprocal transferexperiments in glasshouse compartments at five temperature regimes(means of 13.7, 19.2, 22.3, 25.0 and 28.7 °C). The lengthof the photoperiod-insensitive juvenile phase of development,when flowering cannot be induced by any environmental stimulus,was sensitive to light integral; low light integrals prolongedthis phase, from 23 d at 2.6 MJ m^-2d^-1to 36 d at 1.6 MJ m^-2d^-1(totalsolar radiation). The length of this development phase was shortest(12.5 d) at 21 °C; it was longer under cooler (21 d at 13.5°C) and warmer temperatures (17.6 d at 28.3 °C). Afterthis phase, time to flowering was influenced greatly by photoperiod,with long days hastening flowering by between 28 and 137 d,compared with short days. Plants also showed some sensitivityto both temperature and light integral during this phase, butthe duration of the final phase of flower development, duringwhich plants were photoperiod-insensitive, was dependent primarilyon the temperature at which the plants were grown; at 14.5 °C,33.9 d were required to complete this phase compared with 11.4d at 25.5 °C. The experimental approach gave valuable informationon the phases of sensitivity to photothermal environment duringthe flowering process, and could provide the basis of a morephysiologically-based quantitative model of flowering than hashitherto been attempted. The information is also useful in thescheduling of lighting and temperature treatments to give optimalflowering times of high quality plants.Copyright 1999 Annalsof Botany Company Petunia,Petuniaxhybrida, juvenility, flowering, photoperiod, temperature, light integral, reciprocal transfer.     

Phases of Development to Flowering in Opium Poppy (Papaver somniferumL.) under Various Temperatures

Development up to flowering in opium poppy (Papaver somniferumL.)has been divided into four phases from emergence to anthesiswhich mark changes in its sensitivity to photoperiod: a photoperiod-insensitivejuvenile phase (JP), a photoperiod-sensitive inductive phase(PSP), a photoperiod-sensitive post-inductive phase (PSPP) anda photoperiod-insensitive post-inductive phase (PIPP). To predictflowering time under field conditions, it is essential to knowhow these phases are affected by temperature. Plants were grownin artificially-lit growth chambers and received three differenttemperature treatments: 15/10, 20/15 and 25/20 °C in a 12h thermoperiod. Plants were transferred within each temperatureregime from a non-inductive 9 h to an inductive 16 h photoperiodorvice versaat 1–4 d intervals to determine the durationsof the four phases. Temperature did not affect the durationof the first two phases (i.e. JP lasted 3–4 d and PSPrequired 4–5 d). The most significant effect of temperaturewas on the duration of PSPP which was 28, 20 and 17 d at 15/10,20/15 and 25/20 °C, respectively. The temperature effecton PIPP was small (maximum difference of 3 d between treatments)and the data too variable to indicate a significant trend. Ourresults indicate that PSPP is the only phase that clearly exhibitssensitivity to temperature. Days to flower; opium poppy; Papaver somniferumL.; phases of flower development; photoperiod; temperature     

Effects of Temperature and Photoperiod on Flowering in Lentils (Lens culinaris Medic.)

Factorial combinations of three photoperiods (10, 13 and 16h), two day temperatures (18 and 28 C) and two night temperatures(5 and 13 C) were imposed on nodulated plants of six diversegenotypes (cultivars and land-races) of lentil (Lens culinarisMedic.) grown in pots in growth cabinets from vernalized (1.50.5 C for 30d) or non-vernalized seeds (i.e. 144 ‘treatment’combinations). The times from sowing to the appearance of firstopen flowers were recorded. Vernalization, long days and warmtemperatures hastened flowering but genotypes differed in relativesensitivity to each of these factors and in time to floweringin the same most-inductive environment. Rates of progress towardsflowering (i.e. 1/f the reciprocals of the times to first flower,f) in all genotypes, vernalized or not, were linear functionsof both mean temperature,     

The Influence of Temperature on Seed Germination Rate in Grain Legumes: II. INTRASPECIFIC VARIATION IN CHICKPEA (Cicer arietinum L.) AT CONSTANT TEMPERATURES

Positive linear relationships were shown between constant temperaturesand the rates of progress of germination to different percentiles,G, for single populations of each of five genotypes of chickpea(Cicer anetinum L.). The base temperature, T_b, at which therate of germination is zero, was 0·0°C for all germinationpercentiles of all genotypes. The optimum temperature, T_o(G),at which rate of germination is most rapid, varied between thefive genotypes and also between percentiles within at leastone population. Over the sub-optimal temperature range, i.e.from T_b to T_o(G), the distribution of thermal times within eachpopulation was normal. Consequently a single equation was appliedto describe the influence of sub-optimal temperatures on rateof germination of all seeds within each population of each genotype.The precision with which optimum temperature, T_b(G), could bedefined varied between populations. In each of three genotypesthere was a negative linear relationship between temperatureabove T_b(G) and rate of germination. For all seeds within anyof these three populations thermal time at supra-optimal temperatureswas constant. Variation in the time taken to germinate at supra-optimaltemperatures was a consequence of normal variation in the ceilingtemperature, T_o(G)—the temperature at or above which rateof progress to germination percentile G is zero. A new approachto defining the response of seed germination rate to temperatureis proposed for use in germplasm screening programmes. In two populations final percentage germination was influencedby temperature. The optimum constant temperature for maximumfinal germination was between 10°C and 15°C in thesepopulations; approximately 15°C cooler than the optimumtemperature for rate of germination. It is suggested that laboratorytests of chickpea germination should be carried out at temperaturesbetween 10°C and 15°C. Key words: Chickpea, seed germination rate, temperature     

Temperature and photoperiodic control of developmental responses in climatic races of Achillea

Three climatic races of Achillea from central California (20,1400 and 3100 m elevation) were grown under controlled environmentalconditions at 14 combinations of temperature (0–27°C)and photoperiod (8 or 16 hr). Periodic measurements were madeon height and flowering. Dry weights of roots and shoots ofmature plants were determined. The greatest growth in heightand weight for each race occurred at 11°C on long days (16hr). The coastal race (20 m) grew well over a wide range oftemperatures (7–27°C) but the higher elevation races(1400 and 3100 m) grew well only at low temperatures (7–15°C).In contrast to the vigorous elongation and flowering of thecoastal race in short days at nearly all temperatures, racesfrom the higher elevations remained as rosettes. The sub-alpinerace (3100 m) exhibited the highest root-shoot ratios. Floweringpreceded stem elongation in the sub-alpine race but followedstem elongation in the coastal race. Exogenous applicationsof gibberellic acid (500 mg/liter) to rosette high-elevationraces promoted stem elongation and some flowering. Steroid applicationshad little or no effects. The high-elevation races may containa high-temperature sensitive control mechanism for gibberellinproduction. ¹Present address: Faculty of Botany, Ohio State University,Columbus, Ohio, U. S. A. (Received March 7, 1970; )     

Expression of Vernalization Genes in Near-isogenic Wheat Lines: Effects of Night Temperature

Four near-isogenic lines of wheat (Triticum aestivum L.em Thell)were used to compare selected night temperatures for their effectivenessas vernalizing temperatures. All treatments (conducted withina phytotron) had a common day temperature of 20 °C for 12h and night temperatures were 4, 7, 10, 13 and 20 °C. Interpretationof results for reproductive development was confounded by threeinteracting factors, their relative importance varying withgenotype. Firstly, development rate was generally slower atlower night temperatures. Secondly, in contrast, there was atendency for lower night temperatures to hasten developmentrate if vernalization requirements were satisfied. Thirdly,the lower night temperatures provided a more favourable environmentfor leaf production such that for some genotypes, vernalizedplants had higher final leaf numbers than unvernalized plants.Only for the genotype with the strongest vernalization response(vrn1 vrn2) did hastening of development due to vernalizationoverride any delaying effects. For this genotype, 4, 7 and 10°C were vernalizing temperatures. For the other three genotypes,any hastening of development due to vernalization was outweighedby delaying effects of lower night temperatures. Spikelet numberand days to anthesis were positively correlated in three ofthe four genotypes. It appeared that differences in spikeletnumber were a direct result of night temperature influencingthe duration of the spikelet phase and/or rate of spikelet initiation.Plant size at flowering was determined by the differential effectsof night temperature on growth and development rates. Triticum aestivum L., wheat, vernalization, night temperature, isogenic lines