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 Photoperiod and Temperature on Shoot, Root and Rhizome Growth in ThreeLotus uliginosusSchkuhr Populations

The growth of three populations of greater lotus (Lotus uliginosusSchkuhrsyn.L. pedunculatusCav.) was compared at photoperiods of 10,12 and 14 h at a maximum day/minimum night temperature of 21/16°C and at maximum day/minimum night temperatures of 27/22,21/16, 18/13 and 15/10 °C at a photoperiod of 12 h. Shortdays (10 h) favoured root and rhizome development compared tolong days (14 h). A temperature regime of 15/10 °C restrictedrhizome development compared to the 18/13 and 21/16 °C regimes.Shoot growth was restricted at the highest temperature regime(27/22 °C). The cultivar Sharnae had fewer, but heavier,rhizomes than Grasslands Maku; this may indicate adaptationto the dry summers at its site of origin (Algarve, Portugal).The response of rhizome growth to temperature and photoperiodexplains part of the performance of greater lotus in the fieldat a wide range of latitudes. Grazing management to encouragethe persistence ofL. uliginosusin pasture in temperate environmentsmay include the exclusion of grazing livestock in autumn. Inthe sub-tropics, monitoring of rhizome production in the fieldwould be required before deciding the appropriate time intervalbetween grazing.Copyright 1998 Annals of Botany Company Lotus uliginosus(Schkuhr); greater lotus; temperature; daylength; shoots; roots; rhizomes.     

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     

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,     

Flowering of Stylosanthes guianensis in Relation to Juvenility and the Long-Short Day Requirement

Seedlings of Stylosanthes guianensis var. guianensis were grownin long (14 h) days in five temperature regimes for varyingperiods before transfer to short (11 h) days at 30 ?C/21 ?C.The juvenile phase before seedlings responded to inductive conditionswas c. 45–50 d, 50–60 d and 60–70 d for cv.Schofield, cv. Cook and C.P.I. 34906 respectively, which ispositively related to their critical photoperiod for flowering.Temperatures favourable for growth (e.g. 30 ?C/26 ?C) reducedthe juvenile phase in C.P.I. 34906 and in Cook, which did notflower in 11 h days unless previously exposed to more than 18long days. In a second experiment cv. Cook was confirmed as a long-shortday plant. Seedlings were grown for 50 d in a glasshouse withnatural daylength extended to 13, 14, 16 or 24 h before transferto 12 h photoperiods. Cook floral development was positivelyrelated to daylength provenance before transfer and plants incontinuous 12 h did not flower. Shortening daylength after 48 cycles of 12 h to 11.75 h didnot result in continued floral development in Cook plants butcv. Graham plants were initiated or transitional by 75 d. Key words: Stylosanthes guianensis, Photoperiod, Temperature, Flowering     

Effects of Temperature and Photoperiod on Winged Beans [Psophocarpus tetragonolobus (L.) D.C.]

The effects of temperature and photoperiod on winged beans werestudied using 15 University of New Guinea (UPS) selections andfive Sri Lanka (SL) selections. They were grown at 25/20 or30/25 °C day/ night temperature at 11 or 14 h photoperiodwith 12 h thermoperiod. Differences in stomatal density wereobserved among selections and between photoperiods. Higher densitiesoccurred at 14 h photoperiod than at 11 h photoperiod. Whenstomatal density was high due to a photoperiod or temperatureeffect, there was a corresponding increase in leaf area andd. wt of plants. Total chlorophyll content at 25/20 °C was higher at 11 hphotoperiod than at 14 h photoperiod in all selections whilethe total chlorophyll content at 30/25 °C varied with thephotoperiod and selection. Leaf area of SL selections was greater than that of UPS selections.Also greater leaf area was observed at 14 h photoperiod thanat 11 h photoperiod, irrespective of the growing temperature. Temperature was as important as photoperiod in controlling floweringof winged beans. All the UPS selections and two SL selectionsflowered at 11 h photoperiod at 25/20 °C but failed to flowerat the same photoperiod at 30/25 °C indicating an interactionbetween temperature and photoperiod. It is likely that wingedbeans have a narrow photoperiodic range, particularly the SLselections. Psophocarpus tetragonolobus (L.) D.C., winged bean, stomatal density, leaf area, flowering, temperature, photoperiod     

Photothermal Time for Flowering in Faba Bean (Vicia faba) and the Analysis of Potential Vernalization Responses

One cultivar and one land-race of faba bean were subjected to18 potentially vernalizing pre-treatments (constant temperaturesof 1, 5 or 9 °C factorially combined with photoperiods of8 or 16 h d^–1 for 10, 30 or 60 d), and then transferredinto four different growing regimes (‘day’/‘night’temperatures of 18/5 °C or 24/13 °C factorially combinedwith photoperiods of 11 or 16 h d–1). Control plants weregrown entirely in the latter four regimes. The times from sowingto appearance of first open flowers were recorded for all plants.Control plants of the land-race Zeidab Local flowered soonerin long days and in the warmer regime. Pre-treatment reducedthe subsequent time to flower in the four growing-on regimesbut most of the variation in the total time to first flowerfor the pre-treated plants was accounted for by differencesin the combined photothermal time accumulated in the two successiveenvironments - which was predicted by a simple photothermalmodel. Thus, there was neither a specific low-temperature nora short-day vernalization response in this accession. Similarly,no true low-temperature or short-day vernalization responsewas detected in the cv. Maris Bead. However, this UK cultivarflowered later than predicted in the 24/13 °C regime, indicatingthat the 24 °C ‘day’ temperature was supraoptimal.Delays to flowering at 24/13 °C were, however, less evidentwhen plants were grown in long days or following prolonged (30–60d) pre-treatments at cool temperatures. Viciafaba faba, bean, flowering, photoperiodism, vernalization, photothermal time, screening germplasm.     

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     

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     

Effects of Temperature and Photoperiod on Flowering in Chickpeas (Cicer arietinum L.)

Factorial combinations of two photoperiods (12 and 15 h), threeday temperatures (20, 25 and 30 °C) and three night temperatures(10, 15 and 20 °C) were imposed on nodulated plants of ninechickpea genotypes (Cicer arietinum L.) grown in pots in growthcabinets. The times to first appearance of open flowers wererecorded. For all genotypes, the rates of progress towards flowering(the reciprocals of the times taken to flower) were linear functionsof mean temperature. There were no interactions between meantemperature and photoperiod but the longer photoperiod increasedthe rate of progress towards flowering. These effects were independentof both radiation integral (the product of irradiance and photoperiod)and the vegetative stature of the plant. Taken in conjunctionwith evidence from work on other long-day species, it is suggestedthat the photo-thermal response of flowering in chickpeas, overthe range of environments normally experienced by the crop,may be described by the equation: 1/f = a+b     

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     

Environmental Control of Flowering in Barley (Hordeum vulgare). III. Analysis of Potential Vernalization Responses, and Methods of Screening Germplasm for Sensitivity to Photoperiod and Temperature

Three genotypes of barley were subjected to 18 potentially vernalizingpre-treatments, comprising constant temperatures of 1, 5 or9 °C in factorial combination with photoperiods of 8 or16 h d^–1 for 10, 30 or 60 d^–1. These pre-treatedseeds or seedlings, together with non-pre-treated seeds as controls,were then transferred to each of four growing-on regimes, namelyday/night temperatures of 18/5 °C or 24/3 °C in factorialcombination with photoperiods of 11 or 16 h d^–1. The timesfrom sowing to awn emergence were recorded. The warmer growing-onregime (mean 19 °C) was not supra-optimal in long days,but in short days it considerably delayed awn emergence in allthree genotypes. In cv. Athenais there was no specific responseto the potentially vernalizing pre-trcatments: the rate of progresstowards awn emergence could be treated as a linear functionof the integrated responses to temperature and photoperiod actingindependently throughout development. In addition to these responses,cv. Gerbel B and the land-race Arabi Abiad also responded tolow-temperature vernalization and the response became saturatedduring the longer-duration pre-treatments. In Arabi Abiad, therate at which vernalization occurred, and the period requiredto saturate the response, were not greatly influenced by differencein pre-treatment temperature between 1 and 9 °C. In contrast,in Gerbel B the cooler the temperature of pre-treatment thegreater the saturated response to vernalization, the greaterthe effect of each day of pre-treatment, and the shorter theperiod required to saturate the response. Models of the photothennaland vernalization responses were combined in a single entitywhich described the influence of environment on rate of development.Simple germplasm-screening techniques are proposed for genotypecharacterization so that the phenotypic flowering response canbe estimated for any environment Hordeum vulgare L., barley, flowering, phtoperiodism, vernalization, photothennal time, germplasm screening     

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     

新蚜虫疠霉与豌蚜在不同季节性光周期及恒变温组合下的互作反应

在计算机控制模拟的温带地区秋末冬初自然温度与光周期组合条件下,作者对新蚜虫疠霉Pandoraneoaphidis)与豌蚜(Acyrthosiphon pisum)的互作关系进行了研究,试图探索该菌有无与越冬行为有关的前兆反应。时间-剂量-死亡率模型分析显示,恒温20℃下长日照(光照16h/d)和短日照(光照11h/d)对该菌作用于试虫的时间-剂量效应无明显影响,但显著区别于变温(日变幅为5.4-18.9℃,温变速率0.56℃/30min)下相同长短日照处理,变温下长短日照处理之间亦有较显著差异。相同变温下日照长短主要影响试菌对试虫的潜伏期(致死时间)。在变温日照8.0h、9.5h、11.0h、11.5h、12.0h和16.0h下,试菌平均潜伏期分别为15.14d、15.19d、11.79d、13.33d、11.73d和9.21d,明显呈随日照时数增加而递减的趋势即负相关性(a＝15.58,b＝-0.93,r²=0.78,p<0.01),而恒温日照11 h和16h的平均潜伏期为5.85d和5.97d。镜检所有蚜尸,未发现虫菌体的任何异常现象。结果表明,虽然短日照可延长试菌的潜伏期,但试菌在所有温光组合下均保持着对寄主的有效侵染力,并无越冬的前兆行为反应。作者最后讨论了该菌随寄主迁飞而转移至可生存环境并且无法长期在寄主体外生存的可能性。     

Photothermal Time for Flowering in Lentils (Lens culinaris) and the Analysis of Potential Vernalization Responses

Two cultivars of lentils, Laird and Precoz, were subjected to18 potentially vernalizing treatments, comprising constant temperaturesof 1, 5 or 9 °C in factorial combination with photoperiodsof 8 or 16 h for 10, 30 or 60 d. These seeds or seedlings, togetherwith non-vernalized seeds (as controls), were then transferredto four different growing regimes (‘day’/‘night’temperatures of 18/5 °C or 24/13 °C, factorially combinedwith photoperiods of 11 or 16 h). Variation in the number ofdays from sowing to first flower (f) in the growing regimesfor the controls conformed to the equation I/f = a+b+cP, whereis mean temperature (°C), P is photoperiod (h) and a, band c are genotype-specific constants. Accordingly, when theenvironment varies during development, the photothermal timerequired to flower in day-degrees (°C d) is given by 1/babove a base temperature defined as —(a+cP)/b. Most variationin time to flower could be accounted for by the photothermaltime accumulated in the two successive environments. Therefore,there was no evidence of a specific low-temperature vernalizationresponse in either cultivar. Neither was there evidence of ‘short-day’vernalization, i.e. advancement of flowering resulting frompreliminary short-day treatments. A potential error inherentin the predictive model described arises because it ignoresthe presence of a pre-inductive, photoperiod-insensitive phase;but agro-ecological considerations suggest that this error maynot be important in practice. Lens culinaris, lentil, flowering, photoperiodism, vernalization, photothermal time, screening germplasm     

Regulation of flowering time using temperature,photoperiod and spermidine treatments in Anoectochilus roxburghii

This study investigated the effects of different temperatures, photoperiods and spermidine concentrations on the flowering time regulation of Anoectochilus roxburghii by measuring changes in the soluble sugar, soluble protein, malondialdehyde and proline contents, and the peroxidase, superoxide dismutase and catalase activities in A. roxburghii flower buds. The flowering time could be advanced under 25/20 °C (day/night), 16/8-h (day/night) long day conditions or low spermidine concentrations. The plants grew more rapidly and flowering rates were greater. The flowering time could be delayed under a low temperature of 20/15 °C or 8/16-h short day conditions, resulting in a low flowering rate. Under a high temperature of 30/25 °C or high spermidine concentrations, the plants could not flower normally and even died. There were significant differences in the seven measured indices among the various treatments. Thus, different treatments had significant effects on the flowering time regulation and flowering quality of A. roxburghii, providing a reliable theoretical basis for further studies on the flowering-related regulatory mechanisms of A. roxburghii.     

Effects of Temperature and Photoperiod on Growth and Development of Tillers and Rhizomes in Poa pratensis L. Ecotypes

The vegetative growth of four Norwegian ecotypes of Poa pratensisL. was compared at day/night temperatures of 21/12, 21/6, 12/12and 12/6 °C and at photoperiods of 12, 16, 20 and 24 h,the irradiation being approximately equal in all treatments.Tillering within tufts was most abundant in short days and atthe large temperature amplitude. Rhizome formation and elongationwere stimulated by long days and, more strongly, by high daytemperature, but a greater proportion of the rhizomes formedaerial tillers in short days. Long day stimulation of heightgrowth and dry matter accumulation differed between ecotypesbut was generally most pronounced at low temperatures. The NorthNorwegian ecotype ‘Lavang’ had a higher relativegrowth rate and developed two to three times as many rhizomesas its South Norwegian counterparts. Day/night temperature, growth rate, leaf area, photoperiodicity, Poa pratensis L., rhizomes, roots, smooth meadow grass, tillering, weight gain     

Effect of Temperature on Nitrogenase Activity in White Clover

Single, clonal plants of white clover were grown without inorganicnitrogen in four contrasting day/night temperature regimes,with a 12 h photoperiod, in controlled environments. Root andnodule respiration and acetylene reduction activity were measuredin a flow-through system during both day and night for plantsacclimated to day/night regimes of 23/18, 15/10 and 10/5 ?C.Similar measurements were made on plants acclimated to 20/15?C and stepwise at temperatures from 4 to 33 ?C. Peak rate of ethylene production, nitrogenase-linked respirationand basal root + nodule respiration increased approximatelylinearly from 5 to 23 ?C both in temperature-acclimated plantsand in plants exposed to varying measurement temperatures. Themeasured attributes did not vary significantly between day andnight. Temperatures above 23–25 ?C did not further enhancethe rate of ethylene production, which remained essentiallythe same up to the maximum measured temperature of 33 ?C. The measurements of nitrogenase-linked respiration between 5and 23 ?C, during both day and night, demonstrated a constant‘energetic cost’ of acetylene reduction of 2.9 µmolCO₂ µmol C₂H₄^–1,. Over the same temperature range,the approximate activation energy of acetylene reduction was60 kJ mol^–1. The integrated day plus night nitrogenase-linkedrespiration accounted for 13.4–16% of the plant‘snet shoot photosynthesis in a single diurnal period: there wasno significant effect of temperature between 5 and 23 ?C. Key words: Trifolium repens, white clover, temperature, N₂ fixation, respiration     

Obligate Requirement of Salicylic Acid for Short-Day Induction of Flowering in a New Duckweed, Wolffiella hyalina 7378

Wolffiella hyalina 7378, a member of the Lemnaceae, does notflower in the basal media of Bonner-Devirian, Hoagland, Hutner(1/2 strength), M medium of Hillman or Pirson-Seidel under eitherlong or short day photoperiodic regimes. Well-known chelatingagents, such as EDTA, EDDHA and 8-hydroxyquinoline, which havebeen shown to significantly influence flowering in other membersof the Lemnaceae, also do not show any effect in this strain.It is, however, noteworthy that W. hyalina 7378 flowers profuselyunder a short-day photoperiodic schedule of 8 h light and 16h darkness provided that 10^–5 M salicylic acid is supplementedto modified Bonner and Devirian medium. The critical daylengthof W. hyalina 7378 is 13 h. Further, at least two inductivephotocycles are required for initiation of flowering. As tothe mechanism of SA action, it appears that SA effect on floweringis hormonal in nature rather than due to chelation of metalions. (Received August 25, 1986; Accepted January 9, 1987)     

Phenological Development in Bambara Groundnut (Vigna subterranea) at Constant Exposure to Photoperiods of 10 to 16 h

The flowering and fruit-set of a bambara groundnut selectionfrom Ankpa, Nigeria, were studied in greenhouses at constantexposure to photoperiods of 10, 12, 12·5, 13, 14 and16 h. The development of embryos was determined in ovaries fromplants under photoperiods of 11·5 h and 14 h. The beginningof flowering, recorded as the number of days from sowing tothe first open flower, was delayed by lengthening the photoperiod.It started 7 d later under 16 h than under 10 h. This differenceincreased during the production of the next nine open flowers.Lengthening the photoperiod also caused a delay in the beginningof fruit development. Under 13 h it was delayed by more than40 d compared with fruit development under 10 h. Some plantsunder 14 and 16 h even failed to produce pods. After the beginningof fruit development dry matter partitioning to pods was substantiallyless under 14 and 16 h photoperiods than under photoperiodsof 13 h or less; this was reflected in a strong reduction ofpod growth rates. Under an 11·5 h photoperiod two groups of ovaries couldbe distinguished. In both, embryo development was identicalup to 17 d after anthesis, but then the embryos in the firstgroup continued to develop until they were full-grown at about41 d after anthesis, whereas the growth of the embryos in thesecond group stopped. Embryo development under a photoperiodof 14 h was similar to that in the ovaries with discontinuedembryo growth under the 11·5 photoperiod. Healthy-lookingembryos were found in ovaries up to 32 d after anthesis undera photoperiod 14 h. From then onwards embryos started to shriveland degenerate. Finally, the ovaries aborted.Copyright 1993,1999 Academic Press Vigna subterranea, Voandzeia subterranea, bambara groundnut, phenology, photoperiod, day-length, embryo development, harvest index, dry matter partitioning