Variation in the Durations of the Photoperiod-sensitive and Photoperiod-insensitive Phases of Post-first Flowering Development in Maturity Isolines of Soyabean [Glycine max(L.) Merrill] 'Clark'

Plants of eight isolines of soyabean [Glycine max(L.) Merrill],comprising all combinations of two alleles at the three lociE₁/e₁,E₂/e₂andE₃/e₃inthe cultivar ‘Clark’ background, were transferredafter different periods following first flowering from longdays (LD, 14 h d^-1) to short days (SD, 12 h d^-1) andvice versaina reciprocal-transfer experiment in a plastic house maintainedat 30/24 °C (day/night). Photoperiod (0.10>P>0.05),transfer time (P<0.001),>isoline (P<0.001), and theirinteractions (P<0.001) all affected flowering duration, i.e.the period from first flowering until the appearance of thelast flower. The flowering duration comprised two distinct phases:a photoperiod-sensitive phase beginning at first flowering,and a subsequent photoperiod-insensitive phase. The durationof the photoperiod-sensitive phase varied much more among theisolines in LD than in SD. Only the dominant alleleE₁increasedthe sensitivity of the photoperiod-sensitive phase of floweringduration to photoperiod singly, but positive epistatic effectswere detected betweenE₁andE₂,E₁andE₃, and especially among allthree dominant alleles. The increases in flowering durationresulting from the combined effects of gene and environment(i.e. photoperiod) were associated with considerable increasesin biomass and seed yield at harvest maturity.Copyright 1998Annals of Botany Company. Glycine max(L.) Merrill, soyabean, maturity genes, flowering, photoperiod, reciprocal transfer, yield.     

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     

Effects of Photoperiod and Maturity Genes on Plant Growth, Partitioning, Radiation Use Efficiency, and Yield in Soyabean [Glycine max(L.) Merrill] 'Clark'

Plants of four isolines of soyabean [Glycine max(L.) Merrill]‘Clark’, viz‘L71-920’ (maturity genecomplemente₁e₂e₃ ), ‘L80-5914’ (E₁e₂e₃), ‘Clark’(e₁E₂E₃), and ‘L65-3366’ (E₁E₂E₃), were grown inshort (12.25 h d ^{- 1}natural light) and long days (12.25 h d^{- 1}natural light supplemented with 2.75 h d ^{- 1}low-irradianceartificial light) from first flowering to maturity in a polythenetunnel maintained at 30/24°C (day/night). Whereas therewere few differences among the isolines grown in short days,in long days the dominant alleles increased crop duration, biomassand seed yield substantially. Increases in biological and economicyield were not solely a consequence of longer crop duration:the dominant alleles also increased crop growth rate and radiationuse efficiency in long days (from 1.3 g MJ ^{- 1}total radiationine₁e₂e₃ to 2.8 g MJ ^{- 1}inE₁E₂E₃ ). Greater radiation use efficiencyresulted from a relatively longer leaf area duration, betterdistribution and orientation of a larger mass of leaves withinthe canopy, and smaller partitioning of assimilates to reproductivestructures. The work reveals the substantial effects of thethree lociE₁ / e₁, E₂/ e₂and E₃/e₃ on the response of plantgrowth, as well as development, to environment. Their relevanceto crop adaptation is discussed. Copyright 2000 Annals of BotanyCompany Glycine max(L.) Merrill, soyabean, maturity genes, flowering, phenology, growth, yield     

Characterization of Photothermal Flowering Responses in Maturity Isolines of Soyabean [Glycine max (L.) Merrill] cv. Clark

All eight isolines of three maturity genes (E₁/e₁, E₂ /e₂, andE₃ /e₃) of soyabean [Glycine max (L.) Merrill] cv. Clark weregrown in widely different combinations of photoperiod and temperature.Under the more inductive conditions, i.e. in a warm mean temperature(30°C) when daylengths were less than the critical value(i.e. less than about 13 h), the isolines flowered at similartimes (23-24 d). The responses of all isolines to temperaturewere also similar, if not identical. Increase in daylength abovethe critical photoperiod progressively delayed flowering untilthe time taken to flower (f) reached a maximum at the ceilingphotoperiod. The relations between the rate of progress towardsflowering (1/f) and photoperiod (between the critical and ceilingvalues) were linear. The coefficient characterizing the slopeof the response (photoperiod sensitivity) varied amongst theisolines. These responses could be grouped into three categoriesof increasing sensitivity: (1) least sensitive, e₁e₂e₃ , e₁E₂e₃, e₁e₂E₃ ; (2) intermediate, E₁e₂e₃ , e₁E₂E₃ ; and (3) mostsensitive, E₁E₂e₃, E₁e₂E₃ , E₁E₂E₃ . Thus, in the Clark cultivargenetic background, E₁ induces greater photoperiod sensitivitybut neither E₂ nor E₃ on their own have any effect. However,both E₂ and E₃ together induce photoperiod sensitivity comparableto that induced by E₁ alone. Furthermore, in addition to thisepistasis, either E₂ or E₃ has considerable epistatic effecton E₁, further increasing photoperiod sensitivity. The effectsof these genes and their epistasis were also reflected in theextent of the maximum delays to flowering which occur when theceiling photoperiod is exceeded, and also possibly in earlinessin circumstances when photoperiods were below the critical value.Copyright1994, 1999 Academic Press Glycine max (L.) Merrill, soyabean, maturity genes, flowering, photoperiod, temperature     

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     

Durations of the Photoperiod-sensitive and Photoperiod-insensitive Phases of Development to Flowering in Four Cultivars of Soyabean [Glycine max (L.) Merrill]

Four cultivars of soyabean [Glycine max (L.) Merill] of diverseorigin were grown in pots in a plastic-house maintained at day/nighttemperatures of 30/20°C. Plants were transferred at varioustimes after sowing from short (11·5 h d^-1) to long (13·5h d^-1) days and vice versa. The times from sowing to first floweringfor control plants grown continuously in short days varied from38 to 53 d, whereas the flowering of plants grown continuouslyin long days was delayed by about 20 d in each cultivar. Theduration of the initial photoperiod-insensitive phase (oftencalled the juvenile phase) varied three-fold between cultivars,i.e. from 11 to 33 d. As expected, the duration of the photoperiod-sensitivephase was greater in long days, but there was comparativelylittle genetic variation in photoperiod-sensitivity as definedin terms of days delay in time to flowering per hour increasein photoperiod (9-11 d h^-1). Similarly, there was little variationin the photoperiod-insensitive post-inductive phase; it rangedfrom 15 to 20 d. In consequence, the duration of the initialphotoperiod-insensitive phase was a strong determinant of timeto first flowering in these cultivars. The importance of thisso-called juvenile trait is discussed in terms of preventingthe premature flowering of USA-adapted cultivars when grownin short tropical daylengths and thus improving the adaptationof the crop to the lower latitudes.Copyright 1993, 1999 AcademicPress Glycine max (L.) Merill, soyabean, photoperiodism, juvenility, flowering     

Simulation and Prediction of Plant Phenology for Five Crops Based on PhotoperiodxTemperature Interaction

This paper presents a plant phenological model based on genotypextemperaturexphotoperiodinteraction (GPTmodel). In the model, rate of development towardsa specified stage (e.g. flowering) for a given genotype is composedof three components: the genotype's maximum rate of development;any delay due to a non-optimal temperature; and any delay dueto a photoperiod response. It is assumed that development tothe specified stage is an autonomous process established bymost, if not all, genes other than the vernalization genes andthe photoperiod genes; and that this autonomous process is delayedby any activity of the photoperiod genes. Since all physiologicalprocesses are modulated by temperature, any photoperiod responseis inevitably a photoperiodxtemperature interaction. This interactionis simulated by assuming that the photoperiod gene activityoccurs only beyond a critical photoperiod (P_c) and is enlargedby temperature above a base temperature (T_bp) that allows thephotoperiod gene activity. The model is written asR=1/D_b-S_t(T-T_opt)²-S_p(T-T_bp)|P-P_c|, whereRis the expected rate of development to the specifiedstage under any combination of temperature (T) and photoperiod(P). The other model parameters are:S_p, the sensitivity to adelaying photoperiod;T_opt, the optimum temperature for developmentin the absence of the photoperiod response;S_t, the sensitivityto a non-optimum temperature; andD_b, the basic duration to thespecified stage (or intrinsic earliness), the inverse of whichis the maximum rate of development.D_bis observable only ifT=T_optandsimultaneouslyP     

Differential Effects of Day and Night Temperature on Development to Flowering in Rice

There are conflicting reports with regard to difference in effectsof day temperature (T_D) and night temperatures (T_N) on plantdevelopment. The objective of this study is to determine whetherthere are different effects ofT_DandT_Non development from sowingto flowering in rice (Oryza sativaL.). Plants of 24 rice cultivars were grown in naturally-lightedgrowth chambers at five diurnally constant (22, 24, 26, 28 and32 °C) and four diurnally fluctuating temperatures (26 /22,30 /22, 22 /26 and 22 /30 °C forT_D/T_Nwith 12hd^-1each) witha constant photoperiod of 12hd^-1. The treatments were selectedto enable the separation of effects ofT_DandT_Non developmentrate (DR). The response of DR to constant temperatures was typically nonlinear.This nonlinearity could not explain the difference in floweringdates between fluctuating temperatures with the same mean dailyvalue but oppositeT_D/T_Ndifferences. Differential effects ofT_DandT_NonDR to flowering were detected in all but one cultivar. In mostcases,T_Dexerted a greater influence thanT_N, in contrast withmany previous reports based on the assumption of a linearitybetween DR and temperature. The data were further analysed bya nonlinear model which separated effects ofT_DandT_N. The estimatedvalue for the optimumT_Nwas generally 25 –29 °C, about2 –4 °C lower than the estimated optimumT_Din mostcultivars. The effects ofT_DandT_Non DR were found to be interactivein some cultivars. These results form a new basis for modellingflowering dates in rice. Oryza sativa; rice; flowering; development; day and night temperature; thermoperiodicity     

Time of Flowering of Pea (Pisum sativum L.) as a Function of Leaf Appearance Rate and Node of First Flower

In order to assess the influence of environmental conditionson time of flowering of pea (Pisum sativum L.), a serial sowingtrial was conducted over 2 years at Dijon, France, on two wintercultivars Frisson and Frilene. Time of flowering was analysedaccording to two variables: the leaf appearance rate R_L andthe node of first flower N_I. R_L was linearly related to temperature (r² = 0·94). Thebase temperature was 2°C for both varieties. Growth rateaccounted for the residual variability of R_L . Photoperiod andtemperature acted on N_I in an additive way. Frilene, the latergenotype, was more responsive than Frisson. A model for predicting time of flowering based upon these resultsis proposed. Deviations from this model were related to N nutritionin interaction with the plant water relations. Steps for improvingthe model are then discussed.Copyright 1993, 1999 Academic Press Pisum sativum L., pea, flowering, temperature, photoperiod, phyllochron, model     

Use of field observations to characterise genotypic flowering responses to photoperiod and temperature: a soyabean exemplar

Thirty-nine accessions of soyabean [Glycine max (L.) Merrill] and 1 of wild annual soyabean (Glycine soja L.) were sown at two sites in Taiwan in 1989 and 1990 and on six occasions during 1990 at one site in Queensland, Australia. On two of the occasions in Australia additional treatments extended natural daylengths by 0.5 h and 2 h. The number of days from sowing for the first flower to appear on 50% of the plants in each treatment was recorded (f), and from these values the rate of progress towards flowering (1/f) was related to temperature and photoperiod. In photoperiod-insensitive accessions it was confirmed that the rate is linearly related to temperature at least up to about 29°C. In photoperiod-sensitive genotypes this is also the case in shorter daylengths but when the critical photoperiod (P _c) is exceeded flowering is delayed. This delay increases with photoperiod until a ceiling photoperiod (P _ce) is reached. Between P _c and P _ce, 1/f is linearly related to both temperature (positive) and photoperiod (negative), but in photoperiods longer than P _ce there is no further response to either factor. The resulting triple-intersecting-plane response surface can be defined by six genetically-determined coefficients, the values of which are environment-independent but predict time to flower in any environment, and thus quantify the genotype x environment interaction. By this means the field data were used to characterise the photothermal responses of all 40 accessions. The outcome of this characterisation in conjunction with an analysis of the world-wide range of photothermal environments in which soyabean crops are grown lead to the following conclusions: (1) photoperiod-insensitivity is essential in soyabean crops in temperate latitudes, but such genotypes flower too rapidly for satisfactory yields in the tropics; (2) photoperiod-sensitivity appears to be essential to delay flowering sufficiently to allow adequate biomass accumulation in the warm climates of the tropics; (3) contrary to a widely held view, some degree of photoperiod-sensitivity is also needed in the tropics if crop-duration homeostasis is required where there is variation in sowing dates (this is achieved through a photoperiod-controlled delay in flowering which counteracts the seasonal increase in temperature that is correlated with increase in day-length); and (4) a greater degree of photoperiod-sensitivity is necessary to provide maturity-date homeostasis for variable sowing dates — a valuable attribute in regions of uncertain rainfall. Since the triple-intersecting-plane response model used here also applies to other species, the use of field data to characterise the photothermal responses of other crops is discussed briefly.     

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.     

Floral Induction in a Photoperiodically Neutral Duckweed, Lemna paucicostata Strain LP6: Role of Chelating Agents and Iron

Lemna paucicostata, strain LP₆, does not ordinarily flower underany photoperiodic schedule, when grown in the modified Bonner-Devirianmedium supplemented with 10^–4 M EDTA and 1% sucrose (thisis a medium which is otherwise satisfactory for short day inductionof flowering of other strains of this duckweed). However, when the ferric citrate concentration in the culturemedium containing EDTA was raised 10-fold over that in the normalmedium, a low but significant flowering could be initiated inthis duckweed, irrespective of the length of the photoperiod.A similar flowering response was obtained when ferric citratewas replaced by ferrous sulphate or ferric chloride, therebyindicating that the inductive effect of higher level of ferriccitrate on flowering in strain LP₆ is due to its iron component. Some flowering in this strain could be induced even in mediumcontaining normal level of iron, provided the level of EDTA,itself, was raised to 5?10^–4 (5% flowering) or to 10^–3M (12% flowering), but replacement of EDTA by EDDHA led to trulyremarkable effects. With EDDHA, flowering could be induced at very high levels (90%)under all photoperiodic regimes tried. Floral initiation couldbe obtained even with 10^–6 M EDDHA, though the optimallevel ranged from 5?10^–6 to 10^–5 M. (Received October 4, 1985; Accepted June 26, 1986)     

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 Gibberellic Acid and Naphthaleneacetic Acid on Petiole Senescence and Subtended Peduncle Growth of Cyclamen persicum Mill

Removal of the blade from the leaf subtending the first flowerbud on Cyclamen persicum ‘Swan Lake’ plants causedthe petiole of that leaf to senesce, but had no effect on thegrowth of the flower peduncle in the debladed petiole's axil.A 10 mg NAA l^–1 application generally had no effect onpetiole senescence, peduncle elongation or flowering date whenapplied to the cut end of the petiole after blade removal. A25 mg GA₃ l^–1 application or a combination of 25 mg GA₃l^–1 application or a combination of 25 mg GA₃ l^–1plus 10 mg NAA l^–1 delayed petiole senescence and enhancedpeduncle elongation and subsequent flowering. No treatment significantlyaltered peduncle length at the time of flowering. Cyclamen persicum Mill, ‘Swan Lake’, tissue receptivity, flowering, GA₃, NAA     

Quantal Response of Seed Germination in Seven Genera of Cruciferae to White Light of Varying Photon Flux Density and Photoperiod

The response of the germination of seeds of Barbarea vema (Mill.)Aschers, Brassica chinensis L., Brassica juncea (L.) Czern.& Coss., Brassica oleracea L. var. gongylodes L., Camelinasaliva (L.) Crantz, Eruca saliva Mill., Lepidium sativum L.,Nasturtium officinale R. Br., and Rorippa palustris (L.) Besserto white fluorescent light of different photon flux densitiesapplied for different daily durations in a diurnal alternatingtemperature regime of 20 °C/30 °C (16 h/8 h) was quantifiedby linear relations between probit percentage germination andthe logarithm of photon dose, the product of photon flux densityand duration. The low energy reaction, in which increasing dosepromotes germination, was detected in all the seed populationsbut in Barbarea vema and Brassica Juncea the lowest photon doseapplied (10^–5–2 and 10^{–5 7} mol m^–2 d^–1,respectively) was sufficient to saturate the response. Comparisons,where possible, between photoperiods demonstrated reciprocity,i.e. germination was proportional to photon dose irrespectiveof photoperiod, for the low energy reaction in Brassica oleracea(1 min d^–1 to 1 h d^–1), Camelina saliva (1 min d^–1to 8 h d^–1), Eruca saliva (1 min d^–1 to 24 h d^–1),Lepidium sativum (I min d^–1 to 8 h d^–1) and Rorippapalustris (1 min d^–1 to 8 h d^–1), but not in Brassicachinensis and Nasturtium officinale. The high irradiance reaction,in which increasing dose inhibits germination, was detectedin Barbarea vema, Brassica chinensis, Brassica juncea, Brassicaoleracea, and Camelina saliva. The minimum dose at which inhibitionwas detected was lO^–0–3 mol m^–2 d^–1.These results are discussed in the context of devising optimallight regimes for laboratory tests intended to maximize germination The response of germination to photon dose was also quantifiedwith 3 x 10^–4 M GA₂, co-applied (Brassica chinensis, Camelinasaliva, and Lepidium sativum) and with 2 x 10^–2 M potassiumnitrate co-applied (Brassica chinensis). In the latter casepotassium nitrate had no effect in the dark and inhibited germinationin the light, but GA₂, promoted germination substantially inall three species. Variation amongst seeds in the minimum photondose required to stimulate germination was not affected by co-applicationof GA₂, in Brassica chinensis and Camelina saliva, whereas seedsof Lepidium salivum showed a narrower distribution of sensitivitiesto the low energy reaction in the presence of GA₂ Barbarea vema (Mill.) Aschers, Brassica chinensis L., Brassica juncea (L.) Czern. & Coss., Brassica oleracea L. var. gongylodes L., Camelina saliva (L.) Crantz, Eruca saliva Mill., Lepidium satiaum L., Nasturtium officinale R. Br., Rorippa palustris (L.) Besser, Cruciferae, light, gibberellic acid, seed germination, seed dormancy     

A model for phosphocreatine resynthesis

Nevill, Alan M., David A. Jones, David McIntyre, Gregory C. Bogdanis, and Mary E. Nevill. A model forphosphocreatine resynthesis. J. Appl.Physiol. 82(1): 329-335, 1997.A model for phosphocreatine (PCr) resynthesis is proposed based on a simple electric circuit, where the PCr store in muscle is likened to thestored charge on the capacitor. The solution to the second-order differential equation that describes the potential around the circuitsuggests the model for PCr resynthesis is given byPCr(t) = R  [d₁ ^· exp(k₁ ^· t) ± d₂ ^· exp(k₂ ^· t)],where R is PCr concentration at rest,d₁,d₂, k₁, andk₂ are constants, andt is time. By using nonlinear leastsquares regression, this double-exponential model was shown to fit thePCr recovery data taken from two studies involving maximal exerciseaccurately. In study 1, when themuscle was electrically stimulated while occluded, PCr concentrations rose during the recovery phase to a level above that observed at rest.In study 2, after intensive dynamicexercise, PCr recovered monotonically to resting concentrations. Thesecond exponential term in the double-exponential model was found tomake a significant additional contribution to the quality of fit inboth study 1 (P < 0.05) andstudy 2 (P < 0.01).

     

Dynamics of Carbon Photosynthetically Assimilated in Nodulated Soya Bean Plants under Steady-state Conditions 1. Development and Application of 13CO2 Assimilation System at a Constant 13C Abundance

A long-term, steady-state ¹³CO₂ assimilation system at a constantCO₂ concentration with a constant ¹³C abundance was designedand applied to quantitative investigations on the allocationof photoassimilated carbon in nodulated soya bean (Glycine maxL.) plants. The CO₂ concentration in the assimilation chamberand its ¹³C abundance were maintained constant with relativevariances of less than ±0.5 per cent during an 8-h assimilationperiod. At the termination of 8-h ¹³CO₂ assimilation by plantsat early flowering stage, the currently assimilated carbon relativeto total tissue carbon (measured by the degree of isotopic saturation)were for young leaves (including flower buds), 13.9 per cent;mature leaves, 15.7 per cent; stems+petioles, 5.9 per cent;roots, 5.4 per cent and nodules, 6.9 per cent, 48 h after theend of the ¹³CO₂ assimilation period, they were 12.3, 7.5, 7.4,6.8 and 6.1 per cent, respectively. The treatment with a highconcentration of nitrate in the nutrient media significantlydecreased the allocation of ¹³C into nodules. Experiments on¹³CO₂ assimilation by plants at the pod-filling stage were alsoconducted. Labelling by ¹³C was weaker than at the early floweringstage, but an intense accumulation of ¹³C into reproductiveorgans was observed. Glycine max L., nodulated soya bean plants, ¹³CO₂ assimilation, carbon dynamics     

Production of Oikopleura longicauda (Tunicata: Appendicularia) in Toyama Bay, southern Japan Sea

Oikopleura longicauda occurred throughout the year in ToyamaBay, southern Japan Sea, and analysis of its size compositionand maturity revealed that reproduction was continuous overtheyear. Somatic growth production (P_g) varied with season from0.03 to 103 mg carbon (C) m^–2day^–1 (annual P_g 4.5g C m^–2), and house production (P_e) from 0.11 to 266 mgC m^–2 day^–1 (annualP_e 11.3 g C m^–2). The annualP_g/B ratio was 176. Compared with production data of some predominantzooplankton species in Toyama Bay, it is suggested that despitetheir smaller biomass, appendicularians are an important secondaryproducer.     

Flower-Promoting Effects of Iron and EDDHA in Lemna paucicostata 151

Lemna paucicostata 151 cultured in 1/10 strength M medium containing50 µM FeCl₃ easily flowered in response to short days,although it scarcely flowered under any photoperiod when themedium contained the standard amount of iron (2 µM FeCl₃).The flowering response was accomparied by an increase in theiron content of the plants, which was maximal at pH 5.0. Instandard M medium containing 50 µM FeCl³, this plant didnot flower even though it had a high iron content. Ethylenediamine-di (o-hydroxyphenylacetic acid) (EDDHA) inducedflowering of this strain under continuous light even in theabsence of iron and copper, and its effect was slightly loweredby the presence of iron in the medium. Thus the flower-inducingactivity of EDDHA could not be attributed to the action of ironor copper. EDTA inhibited both the iron uptake and floweringin Fe-rich medium under short-day conditions. (Received May 16, 1986; Accepted July 25, 1986)