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     

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     

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     

Temperature and Seed Storage Longevity

Seed survival data for eight diverse species, namely the cerealbarley (Hordeum vulgare L.), the grain legumes chickpea (Cicerarietinum L.), cowpea [Vigna unguiculata (L.) Walp.] and soyabean [Glycine max (L.) Merr.], the timber trees elm (Ulmus carpinifoliaGleditsch.), mahogany (Swietenia humilis Zucc.), and terb (Terminaliabrassii Exell.), and the leaf vegetable lettuce (Lactuca sativaL.) were compared over a wide range of storage environments(temperatures from –13 °C to 90 °C, seed moisturecontents from 1.8 to 25% f. wt) using a viability equation developedpreviously. In accordance with that equation, the effect oftemperature on seed longevity was dependent upon the temperaturerange. The temperature coefficients of the viability equationdid not differ significantly (P > 0.05) among the eight speciesdespite their contrasting taxonomy. Thus the quantitative relationbetween seed longevity and temperature does not vary among diversespecies. The same conclusion was obtained for the coefficientsof a proposed alternative model of the relation between seedlongevity and temperature. The implications of the two temperaturemodels in the viability equation for extrapolations to low andvery low temperatures are discussed. Seed storage, seed longevity, seed moisture, temperature, viability equation, genetic resources conservation, Cicer arietinum L., Glycine max (L.) Merr., Hordeum vulgare L., Lactuca sativa L., Swietenia humilis Zucc., Terminalia brassii Exell., Ulmus carpinifolia Gleditsch., Vigna unguiculata (L.) Walp     

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     

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     

The Influence of Genotype, Temperature and Moisture on Seed Longevity in Chickpea, Cowpea and Soya bean

Seed of three chickpea (Cicer arietinum L.), three cowpea [Vignaunguiculata (L.) Walp.] and four soya bean [Glycine max (L.)Merr.] cultivars were hermetically stored for up to 2 yearsin various constant environments which included temperaturesfrom —20 to 70 °C and moisture contents (fresh weightbasis) from 5 to 25 per cent. In all cases the survival curvescould be described by negative cumulative normal distributions.The longevity of the various seed lots differed but the valueof the standard deviation (the reciprocal of which gives theslope of the survival curve when percentage germination is transformedto probit) was the same for all cultivars within a species whenstored under similar conditions. Within each species the relativeeffects of moisture and temperature on longevity did not differsignificantly between cultivars. In all three species therewas a negative logarithmic relationship between seed moisturecontent and longevity, but the relative effect of moisture contentdiffered between the species: differences in the longevity ofsoya bean seed as a function of moisture content were less thanfor either cowpea or chickpea. The relative effect of temperatureon seed longevity did not differ between the three species,and the seed of all three species showed increasing temperaturecoefficients for the change in rate of loss of viability withincrease in temperature. The complete pattern of loss in viabilityin all three species can be described by a single equation whichwas developed for barley and has also been shown to apply toonion seed. The constants applicable to the three grain legumeshave been calculated so that it is now possible to predict percentageviability of any seed lot of these species after any storageperiod under a very wide range of storage conditions. Cicer arietinum L., chickpea, Glycine max (L.) Merr., soya bean, Vigna unguiculata (L.) Walp., cowpea, seed longevity, seed storage, moisture content, temperature     

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 Photoperiod, Nitrogen Nutrition and Temperature on Inflorescence Initiation and Development in Onion (Allium cepa L.)

The effects of photoperiod, nitrogen nutrition and temperatureon inflorescence initiation and development in onion cv. Rijnsburgerand cv. Senshyu Semi-globe Yellow were studied in controlledenvironments. Rates of inflorescence initiation were estimatedusing the data for leaf numbers formed prior to flower formationand the rates of leaf initiation. At 9 °C inflorescenceinitiation was accelerated by long photoperiods particularlyfor cv. Rijnsburger where the average time for initiation was86 days in 8 h and 38 days in 20 h photoperiods. Initiationwas as rapid at 12 °C as at 9 °C but was slower at 6°C. A reduction in the nitrate concentration in the nutrientsolution from 0.012 to 0.0018 M greatly accelerated inflorescenceinitiation particularly in photoperiods and temperatures notconducive to rapid initiation. Cv. Senshyu initiated more slowlythan cv. Rijnsburger and was less sensitive to photoperiod andnitrogen level. The development rate of inflorescences afterinitiation was accelerated by long photoperiods and increasesin temperature from 6 to 12 °C but was retarded by the lowernitrogen level. Allium cepa L., onion, flower initiation, inflorescence development, photoperiod, nitrogen nutrition, temperature, vernalization     

Dormancy and Flowering in Anemone coronaria L. as Affected by Photoperiod and Temperature

The effects of day-length and temperature on flowering and dormancyinduction were studied in Anemone coronaria L., with plantsraised either from corms or achenes. An Israeli hybrid sourcewas used (de Caen cv. Hollandia x Israeli wild type). Dormancy onset is characterized by the cessation of foliageleaf production, the appearance of leaf scales protecting theperennating bud, and leaf senescence. Dormancy was induced byhigh temperature and long days but increasing temperatures (from17/12 °C to 32/12 °C) induced earlier dormancy thanprolonging the photoperiod (range 8–16 h). A significant(P = 0.01) interaction was found between these factors, withsmaller photoperiodic effects the higher the temperature. At22/17 °C the critical day-length for dormancy inductionwas between 11 and 12 h. The transition from the vegetative to the reproductive stageappears to be an autonomous process that occurs with developmentin plants raised from either corms or achenes and does not requireenvironmental induction. Photo- and thermoperiodic effects onflowering were indirect, being mediated through their influenceon dormancy induction. Anemone coronaria L., dormancy, flowering, photoperiod, thermoperiod     

Photoperiod Sensitivity during Flower Development of Opium Poppy (Papaver somniferum L.)

Photoperiod is a major factor in flower development of the opiumpoppy (Papaver somniferum L. ‘album DC’) which isa long-day plant. Predicting time to flower in field-grown opiumpoppy requires knowledge of which stages of growth are sensitiveto photoperiod and how the rate of flower development is influencedby photoperiod. The objective of this work was to determinewhen poppy plants first become sensitive to photoperiod andhow long photoperiod continues to influence the time to firstflower under consistent temperature conditions. Plants weregrown in artificially-lit growth chambers with either a 16-hphotoperiod (highly flower inductive) or a 9-h photoperiod (non-inductive).Plants were transferred at 1 to 3-d intervals from a 16- toa 9-h photoperiod andvice versa . All chambers were maintainedat a 12-h thermoperiod of 25/20 °C. Poppy plants becamesensitive to photoperiod 4 d after emergence and required aminimum of four inductive cycles (short dark periods) beforethe plant flowered. Additional inductive cycles, up to a maximumof nine, hastened flowering. After 13 inductive cycles, floweringtime was no longer influenced by photoperiod. These resultsindicate that the interval between emergence and first flowercan be divided into four phases: (1) a photoperiod-insensitivejuvenile phase (JP); (2) a photoperiod-sensitive inductive phase(PSP); (3) a photoperiod-sensitive post-inductive phase (PSPP);and (4) a photoperiod-insensitive post-inductive phase (PIPP).The minimum durations of these phases forPapaver somniferum‘album DC’ under the conditions of our experimentwere determined as 4 d, 4 d, 9 d, and 14 d, respectively. Anthesis; days to flowering; flower bud; opium poppy; Papaver somniferum L.; photoperiod; photoperiod sensitivity; predicting time to flowering; transfer     

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     

Variation in the Durations of the Photoperiod-sensitive and Photoperiod-insensitive Phases of Development to Flowering Among Eight Maturity Isolines of Soyabean [Glycine max (L.) Merrill]

In soyabean [Glycine max (L.) Merrill] the period between sowingand flowering is comprised of three successive developmentalphases—pre-inductive, inductive and post-inductive—inwhich the rate of development is affected, respectively, bytemperature only, by photoperiod and temperature, and then againby temperature only. A reciprocal-transfer experiment (carriedout at a mean temperature of 25°C) in which cohorts of plantswere transferred successively between short and long photoperiodsand vice-versa showed that eight combinations of three pairsof maturity alleles (E₁/e₁, E₂ /e₂, E₃ /e₃) had their greatesteffect on the duration of the inductive phase in long days.This phase was increased with the increasing photoperiod sensitivityinduced by the different gene combinations, and ranged fromabout 27 to 54 d according to genotype. In a short day regime(11·5 h d^-1), less than the critical photoperiod, theduration of the inductive phase was brief—requiring about11 photoperiodic cycles in the less photoperiod-sensitive genotypesand only about seven cycles in the more sensitive ones. Thematurity genes also affected the duration of the two photoperiod-insensitivephases; these durations were positively correlated with thephotoperiod-sensitivity potential of the gene combinations.The largest effect was on the pre-inductive phase which variedfrom 3 to 11 d, while the post-inductive phase varied from about13 to 18 d. As a consequence of these non-photoperiodic effectsof the maturity genes, even in the most inductive regimes (daylengthsless than the critical photoperiod) the time taken to flowerby the less photoperiod-sensitive combinations of maturity geneswas somewhat less than in the more sensitive combinations—rangingfrom about 28 to 34 d. The genetic and practical implicationsof these findings are discussed.Copyright 1994, 1999 AcademicPress Glycine max (L.) Merrill, soyabean, maturity genes, isolines, flowering, photoperiod     

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     

Linear Relations between Carbon Dioxide Concentration and Rate of Development Towards Flowering in Sorghum, Cowpea and Soyabean

Negative linear relations were detected (P < 0·005)between the rate of progress from sowing to panicle initiationand CO₂ concentration (210-720 µmol CO₂ mol^-1 air) fortwo genotypes of sorghum [Sorghum bicolor (L.) Moench]. Relationsbetween CO₂ concentration and the rate of progress from sowingto first flowering were also negative in soyabean [Glycine max(L.) Merrill] (P < 0·025), but positive in cowpea[Vigna unguiculata (L.) Walp.] (P < 0·025), albeitthat in both grain legumes sensitivity was much less than insorghum. Thus CO₂ elevation does not delay flowering in allshort-day species. The considerable effect of CO₂ concentrationon times to panicle initiation resulted in large differencesamong the sorghum plants at this developmental stage; with increasein CO₂ concentration, plants were taller with slightly moreleaves and more pronounced apical extension. At the same timeafter sowing however, sorghum plants were heavier (P < 0·05)at 210 than at 360 µmol CO₂ mol^-1 air. In contrast, relationsbetween the dry masses of the soyabean and cowpea plants andCO₂ concentration were positive and curvilinear (P < 0·05).It is suggested that the impact of global environmental changecould be severe for sorghum production in the semi-arid tropics.Copyright1995, 1999 Academic Press Sorghum bicolor (L.) Moench., sorghum, Glycine max (L.) Merrill, soyabean, Vigna unguiculata (L.) Walp., cowpea, development, flowering, CO₂, dry matter accumulation, environmental change     

Effects of Photoperiod, Temperature and Asynchrony between Thermoperiod and Photoperiod on Development to Panicle Initiation in Sorghum

The duration of the vegetative phase (i.e. days from sowingto panicle initiation) in sorghum [Sorghum bicolor (L.) Moench]is affected by photoperiod and temperature. Plants of severalcontrasting genotypes of sorghum were grown in controlled-environmentgrowth cabinets with either synchronous or asynchronous photoperiodsand thermoperiods. Apical development was recorded. Diurnalasynchrony between photoperiod and thermoperiod reduced durationsto panicle initiation when the temperature warmed after lightswent on and cooled after lights went off, but increased thesedurations when the temperature warmed before lights went onand cooled before lights went off. These effects were shownin the maturity lines 60M and SM100 and also in the USA cv.RS610 and the Sudanese landrace IS22365, but their magnitudevaried with genotype, photothermal regime, and the degree ofasynchrony. The greatest effect was detected in IS22365 grownat 30/21 °C (12 h/12 h) with a 12 h d^-1photoperiod whenthe temperature warmed 2.5 h before lights went on and cooled2.5 h before lights went off, when the duration from sowingto panicle initiation was 69 d compared with 37 d in the control(synchronous photoperiod and thermoperiod in each diurnal cycle). Reciprocal transfers of plants of IS22365 between short andlong days revealed that asynchrony principally affected theduration of the photoperiod-insensitive pre-inductive phaseof development; i.e. asynchrony affected the time (age) at whichthe plants were first able to respond to photoperiod. In thatinvestigation in controlled-environment growth chambers, thesubsequent photoperiod-sensitive inductive phase continued untilpanicle initiation. Subsequent reciprocal transfer experimentsin controlled-environment glasshouses in four different alternatingtemperature regimes employed synchronous photoperiods and thermoperiodsin short (11 h) days with temperature warming 1.5 h after thebeginning of the day in long (12.5 h) days. In those investigations,photoperiod sensitivity ended some time before (2.5–8.1d, mean 5.7 d) panicle initiation in IS22365, Naga White andSeredo. Moreover, whereas the duration of the photoperiod-insensitivepre-inductive phase was affected by temperature, the durationsof the photoperiod-sensitive inductive and the photoperiod-insensitivepost-inductive phases were not. Sorghum bicolor (L.) Moench; sorghum; asynchrony; photoperiod; thermoperiod; vegetative phase; panicle initiation     

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     

Influence of Vernalization and Photoperiod on Supernumerary Spikelet Expression in Wheat

Two tetraploid (Triticum turgidum L.emend gr. turgidum and gr.durum) and five hexaploid wheats (Triticum x aestivum L. emendgr. aestivum) with reported tendencies for ‘branched heads’(supernurnerary spikelets) exhibited variation in its expressionunder different vernalization photoperiod and temperature regimes. Two main types of supernumerary spikelets were identified, multiplesessile spikelets (MSS) with two or more complete spikeletsat a rachis node and indeterminate rachilla spikelets (IRS)with two to 13 spikelets on an extended rachilla. The degree of supernumerary spikelet expression in wheats withvernalization response differed from those without. Short photoperiods(9–14 h) both outdoors and in a glasshouse environment,were more conducive to supernumerary spikelet expression than24 h photoperiod in both environments. The 24 h photoperiodglasshouse environment (higher mean temperatures) was leastconducive to its expression except in lines with a strong vernalizationresponse. The high stability of supernumerary spikelet expression in certaingenotypes in the different environments indicated the feasibilityof incorporating this character in breeding and selecting commercialwheats to increase grain number per head. Triticum, wheat, ear-branching, supernumerary spikelets, vernalization, photoperiod, temperature     

Low Moisture Content Limits to Relations Between Seed Longevity and Moisture

Discontinuities at low moisture contents in the otherwise logarithmicrelations between seed longevity and seed moisture content (%,f. wt basis) in hermetic storage at 65 °C were detectedat 2–0% in groundnut (Arachis hypogaea L.), 3·5%in onion (Allium cepa L.), 4·5% in sugar beet (Beta vulgarisL.), 4·6% in barley (Hordeum vulgare L.), 5·3%in chickpea (Cicer arietinum L.) and wheat (Triticum aestinumL.), and 5·6% in cowpea [Vigna unguiculata (L.) Walp.].In contrast, the equilibrium relative humidity of seeds at thesevalues was similar, varying between 9·9% (onion and sugarbeet) and 11·5% (wheat). The mean value was 10·5%r.h. (s.e. 0.2). There was no significant (P > 0·05)effect of further reduction in seed moisture content below thesecritical values on longevity, except in wheat (P < 0·005),in which there was a further increase in longevity. In soyabean [Glycine max (L) Merrill], the logarithmic relation continueddown to the lowest moisture content investigated, 3·3%(11·4% equilibrium relative humidity). Above the criticalvalue, seed longevity in groundnut showed the least sensitivityto increase in percentage moisture content, while barley showedthe greatest, the values of the viability constant C_w (slopeof the negative logarithmic relation between longevity and moisture)being 4·089 (s.e. 0·278) and 5·966 (s.e.0·325), respectively. These differences in the valueof C_w among the eight crops were significant P < 0·005),whereas the relative sensitivity of seed longevity to changein equilibrium relative humidity above the critical moisturecontent did not differ significantly among the eight (P >0·10) and was equivalent to a doubling of longevity foreach 8·7% reduction in equilibrium relative humidity.Accordingly it is concluded that the relative effect of waterpotential on seed longevity can be considered to be the samefor these and probably also for many other orthodox species. Barley, chickpea, cowpea, groundnut, onion, soya bean, sugar beet, wheat, seed storage, seed longevity, seed moisture content, viability equation, water relations     

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.