Response to Temperature in a Stand of Pearl Millet: 10. PARTITION OF ASSIMILATE

Effects of temperature on partition of assimilate between leaves,stems and panicles of pearl millet are analysed in terms ofa duration (t_w) over which a structure increased in weight,and a partition factor (p)—the fraction of new dry matterallocated to the structure during t_w. The value of tw was, forall structures, inversely proportional to temperature abovea base of 10 °C and below an optimum of 28 to 30 °C.For stems and panicles, the value of p was, with one exception,little affected by temperature. The dry weight of these structureswas, therefore, proportional to t_w, and decreased with risein temperature. (The exception was panicles at the lowest temperature,19 °C, for which p was reduced by 40% because few grainswere set.) For leaves, however, p increased with rise in temperature,counteracting the effect on t_w, such that dry weight changedlittle with temperature. The optimum temperature for reproductiveyield was 22 °C, but the proportion of the total dry matterallocated to reproductive structures changed little between22 °C and 31 °C. Key words: Pearl millet, temperature, thermal time, partitioning     

The Effects of Position and Temperature on the Expansion of Leaves of Vicia faba L.

The growth in area of the first eight leaves of broad bean plantswas investigated in growth room experiments. Plants were grownat either 20 or 14 °C or transferred from 20 to 14 °C.Rates of leaf appearance and unfolding increased with temperature.The duration of growth of a leaf increased with leaf numberfor the first five leaves and then remained constant The meangrowth rate declined or remained constant with increasing leafnumber Durations of growth were shorter and growth rates largerat 20 °C than at 14 °C Plants responded immediatelyto the change in temperature Final areas of leaves which expandedafter transfer from 20 to 14 °C were larger than those grownat 20 °C Vicla faba L., broad bean, leaf expansion, temperature responses     

Effect of Temperature on Interception and Conversion of Solar Radiation by Stands of Groundnut

Stands of groundnut were grown in controlled environment glasshousesat air temperatures of 19, 22, 25, 28, and 31°C. Leaf areaindex (L) increased with rise of temperature, and after 85 dwas about 10-fold larger at 31°C than 19°C. Over mostof the range of temperature, both L and fractional interceptionof solar radiation (f) were functions of thermal time accumulatedfrom sowing (above a base of 10°C). In this respect, theywere tightly coupled to developmental rate at the main apex.In one experiment, only 38% of seeds emerged at 22°C and21% at 19°C, compared with more than 70% at 25°C and31°C, but the low population density was compensated byfaster leaf expansion by each plant (at 22°C only) and agreater fraction of solar radiation intercepted by unit leafarea. The amount of solar radiation intercepted by stands increasedwith rise in temperature, but the greatest differences betweentreatments occurred before the canopies achieved complete groundcover (i.e.f>0.9) and the relative effect of a rise in temperaturediminished the longer the duration of growth. The dry matterproduced for unit solar radiation intercepted was not stronglyaffected by temperature between 22°C and 31°C, wherethe mean was 2.1 g MJ^–1; the value at 19°C was uncertainsince the stands were sparse throughout the experiment. After85 d, the stand at 31°C had produced eight times the drymatter of that at 19°C—a difference caused mainlyby the effect of temperature on the rates of development andexpansion. Key words: Dry matter production, groundnut, radiation interception, temperature, thermal time, roses     

A Comparison of the Effect of High Temperature on Grain Development in Wheat and Rice

Grain weight at maturity of the wheat cultivar Banks was reducedby about 5% for each 1 °C rise in daily mean post-anthesistemperature in the range from 17.7 to 32.7 °C, using grainweight at 17.7 °C as the base. In contrast, the rice cultivarCalrose had a stable grain weight up to 26.7 °C and abovethat showed a 4.4% drop in weight per 1 °C increase in meanpost-anthesis temperatures up to 35.7 °C, using grain weightat 26.7 °C as the base. In both wheat and rice there wasa reduction in the duration of grain growth with increasingtemperature up to a mean of 26.7 °C. In this range rice,but not wheat, showed a compensating increase in the rate ofdry-matter accumulation. Above 26.7 °C the rate of dry-matteraccumulation fell in both species, although this was more stablein rice than in wheat. In wheat the duration of grain growthcontinued to decrease at temperatures above 26.7 °C, butshowed little change in rice up to 35.7°C, the maximum tested.These data are discussed in relation to the physiological, biochemicaland physical constraints that may act to regulate grain developmentin wheat and rice at high temperature. Triticum aestivum, oryza sativa, grain development, high temperature effects     

Temperature Effects on Phenological Development and Yield of Muskmelon

Our goal was to construct a simple muskmelon phenology modelthat could be run with easily obtainable weather station dataand used by growers to quantify phenological development andaid in projecting harvest dates. A growth chamber experimentwas conducted with two cultivars of muskmelon (‘Gold Rush’and ‘Mission’) to determine how main vine leaf appearancerates responded to temperature. We identified three cardinaltemperatures for leaf appearance rate: the base temperature(10 °C) at which leaf appearance rate was zero; an optimumtemperature (34 °C) at which the rate of leaf appearancewas maximal; and an upper threshold temperature (45 °C)at which leaf appearance rate returned to zero. Using thesethree cardinal temperatures, we constructed a simplified thermalunit accumulator for hourly measurements of air temperature.Main vine plastochron interval (PI), thermal time to harvest,and final yield were determined for three cultivars of muskmelon(‘Explorer’, ‘Gold Rush’ and ‘Mission’)grown in the field at Overton, TX, USA, over six transplantingdates from March to June 1998. PI was calculated for each cultivarx transplanting date combination as the reciprocal of the slopeof main vine node number vs. accumulated hourly thermal units(     

The Growth and Development of Maize (Zea mays L.) at Five Temperatures

The objectives of this work were to measure growth and developmentrates over a range of temperatures and to identify processeswhich may limit vegetative yield of maize (Zea mays L.). Twosingle cross Corn Belt Dent maize hybrids were grown from sowingin a diurnal temperature regime of 16/6 °C day/night andin constant temperature environments of 16, 20, 24 and 28 °C.The 16/6 °C environment was close to the minimum for sustainedgrowth and 28 °C was near the optimum. Entire plants wereharvested at stages with 4, 6, 7 and 8 mature leaves in alltemperature treatments except 20 °C in which the final twoharvests were carried out at 9 and 10 mature leaves. Mean totalleaf number varied between 19.5 and 16.0 with the maximum occurringat 16/6 °C. Although harvests were carried out at comparableleaf numbers, and hence at similar developmental stages, thetime interval between sowing and harvest decreased considerablyas temperatures increased. The relative rates of dry weight and leaf area accumulationwith time increased with a Q₁₀ of 2.4 between 16 and 28 °C,while leaf appearance rate increased with a Q₁₀ of 2.9 overthe same range; both rates were highest at 28 °C. Althoughdry matter partitioning to the shoots increased with temperature,the area of individual leaves varied in a systematic patternwhich resulted in maximum leaf area, leaf area duration andconsequently dry weight being realized at 20 °C for anygiven stage of development. Zea mays, corn, low temperature stress, temperature response, growth, development     

The Effect of Heat Stress on Wheat Leaf and Ear Photosynthesis

The effect of heat-hardening on carbon exchange rate per unitarea (CER) of flag leaves, whole ears, and ears with the awnsremoved, was measured in hexaploid (Triticum aestivum L.) andtetraploid (T. turgidum L. and T. dicoccoides) wheat varieties.The CER for awns was calculated by the difference. For the non-hardened hexaploid cv. ‘H-895’ the CERfor the leaves and glumes had an optimum temperature of 25°C.By contrast, the CER for the awns increased from 25°C to32°C, indicating an optimum at 32°C or more. Heat-hardeningdecreased the CER of leaves and glumes at the optimum temperature,but increased the CER especially in leaves at supra-optimaltemperatures. Thus, leaf CER in hardened plants became essentiallyindependent of temperatures between 25°C and 32°C. AwnCER was little affected by heat-hardening. For all 12 varieties, leaf and ear CER was smaller in hardenedplants at 30°C than in non-hardened plants at 22°C.Leaf and ear CER measured at 30°C differed significantlybetween varieties within a species. Whole ear CER at 30°Cwas negative in most varieties although the calculated valuefor the awns was positive. Thus, the high temperature optimumfor CER of the awns was a major factor in the variation amongwheat varieties in tolerance of ear CER to heat. The biochemicalattributes of the photosynthetic mechanism in awns responsiblefor the high temperature optimum were already present in wildtetraploid wheat. There was a positive correlation across allvarieties between ear CER at 30°C and the percentage ofawns in total ear area (r = 0930, P = 0 This together with previousresults (Blum, 1985a), suggests that a large amount of awnsin the ear is a sensible selection index in wheat for improvedproduction in hot, dry environments. Key words: Carbon exchange rate, photosynthesis, awns, heat, stress, wheat, breeding     

The Responsiveness to Temperature of the Extension Rates of Leaves of Wheat Growing in the Field under Different Levels of Nitrogen Fertilizer

The response of the rates of extension (LER) of wheat leaves(Triticum aestivum cv. Gamenya) to temperatures maintained fora short period was measured by changing the temperature of theextension zone and recording the changes in leaf length. Therange of temperatures used was from 4-38 °C. The LER ofall leaves responded to increases in temperature as field temperatureswere suboptimal. The data obtained from several series of measurementsover different ranges of temperature were combined to producea general response curve. The minimum temperature for LER wasconsidered to be approximately 0 °C, the optimum was 28.4°C, while the maximum was in excess of 38 °C. The responsivenessof LER to temperature, measured by the Q₁₀, declined exponentiallyfrom >6 at 5 °C to 2 at 20 °C. The Q₁₀ at 15 °Cwas not affected by nitrogen supply.     

Dormancy in Dioscorea: Range, Duration and Timing of High-Temperature Treatment in Germination Inhibition of D. tokoro Seeds

The effects of temperature on induction and release of high-temperatureinhibition in seed germination of Dioscorea tokoro Makino, amonocotyledonous summer perennial of the temperate zone of EastAsia, were investigated. Germination was increasingly inhibitedwith elevation of temperature over 23°C and lengtheningof its duration. The low temperature limit for germination inhibitiondecreased with lengthening of the duration of high temperature.The most sensitive phase for high temperature was 1–2days after the start of imbibition at 20°C. The germination inhibition by high temperature was reversedby chilling at 5°C, which is the optimum temperature forbreaking the natural dormancy (primary dormancy) of this seed.This showed that the high-temperature inhibition of germinationdoes not cause mortal damage but only secondary dormancy (induceddormancy). Seeds from a cold climate (Miyagi Pref.) responded rather quicklyto both high temperature and chilling compared to seeds froma warm climate (Kagoshima Pref.). The responsiveness to hightemperature and chilling of D. tokoro seed may affect the germinationtime under natural conditions. (Received October 22, 1982; Accepted January 14, 1983)     

The Seasonal Pattern of Growth and Production of a Temperate C4 Species, Cyperus longus

Growth and production of the temperate C₄ species Cyperus longusL. was measured throughout a growing season in an establishedplot in Eastern Ireland. The maximum standing live biomass reachedwas 2·5 kg m^–2. Estimates of unit leaf rate (ULR)and leaf area index (LAI) were made. The product of these quantitiesgave the crop growth rate (CGR) each week. C. longus was foundto maintain high values of LAI throughout the summer, with amaximum value of about 13 in early August. CGR reached a peakin early July. The optimum LAI was 11·6. Temperaturesat five levels in the plant canopy, and the amount of solarradiation intercepted by the canopy were measured continuouslyduring the summer. The mean daily rate of leaf extension waspositively correlated with the mean daily air temperature abovethe canopy but the temperature coefficient of the process waslow compared with other temperate species. The percentage ofsolar radiation intercepted by the canopy increased rapidlyin early summer, and canopy closure had occurred by mid-June.Rates of net photosynthesis were measured on young and old leafmaterial in situ at the time of peak LAI. In young leaves themaximum rates of net photosynthesis were higher than those publishedfor a range of temperate C₃ species, but similar to those foundin another temperate C₄ species, Spartina townsendii. Key words: C₄ photosynthesis, leaf growth, productivity     

Effect of Temperature and Nitrogen Supply on the Growth of Perennial Ryegrass and White Clover. 1. Carbon and Nitrogen Economies of Mixed Swards at Low Temperature

Simulated mixed swards of perennial ryegrass (Lolium perenneL. cv. S23) and white clover (Trifolium repens L. cv. S100)were grown from seed under a constant 10°C day/8°C nighttemperature regime and their growth, and carbon and nitrogeneconomies examined. The swards received a nutrient solution,every second day, which contained either high (220 µgg^–1) or low (40 µg g^–1) nitrate N. The High-N swards had rates of canopy photosynthesis and drymatter production (over the linear phase of growth) similarto those previously shown by mixed swards at high temperature.The Low-N swards grew more slowly; canopy photosynthesis, ata given LAI, was similar to that at High-N but lower LAI's weresustained. Clover increased its contribution to total carbonuptake and total dry weight throughout the period in the Low-Ntreatment and, despite the fact that grass took up most of theavailable nitrate, clover maintained a consistently higher Ncontent by virtue of N₂-fixation. At High-N, grass dominated throughout the measurement period.Earlier, when plants grew as spaced individuals, clover grewless well than grass, but once the canopy was closed it hada similar relative growth rate and thus maintained a steadyproportion of total sward dry weight. It is proposed that earlyin the development of the crop, leaf area production is thelimiting factor for growth, and that in this respect cloveris adversely affected by low temperature relative to grass.Later, as the LAI of the crop builds up, and the canopy becomesfully light intercepting, net canopy photosynthesis plays amore dominant role and here the higher photosynthetic rate perunit leaf area of the clover is crucial. Trifolium repens, white clover, Lolium perenne, perennial ryegrass, low temperature, nitrogen, photosynthesis     

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

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

The Effects of Temperature on Leaf Growth in Cyperus longus, a Temperate C4 Species

Plants of the C₄ sedge Cyperus longus L. were grown at 10, 20and 30 °C. An asymptotic growth curve, the Richards function,was fitted to growth data for successive leaves. The mean rateof leaf appearance was a linear function of temperature with0.014 leaves appearing per day for every 1 °C increase intemperature. The instantaneous relative rate of leaf extensionshowed a marked ontogenetic drift which was most rapid at 30°C and slowest at 10 °C. The mean absolute extensionrate for foliage had a temperature coefficient of 0.16 cm d^–1° C^–1 in the range from 10 to 30 °C. The durationof leaf growth was independent of leaf number at 10 and 20 °Cbut increased linearly with leaf number at 30 °C. The smalldifferences in relative growth rate at the three temperaturesresulted in large differences in foliage area produced at theend of a 30 d growth period. The final foliage areas at 20 and10 °C were 51 and 9% respectively of that at 30 °C. Cyperus longus, temperature, leaf growth, Richards function, growth analysis     

Temperature Response of Vernalization in Wheat: A Developmental Analysis

The vernalization response of wheat ( Triticum aestivum L.)was reinterpreted from a developmental perspective, using currentconcepts of the developmental regulation of wheat morphologyand phenology. At temperatures above 0 °C, the effects ofthe process of vernalization per se in wheat are confoundedby the effects of concurrent vegetative development. These effectsare manifested by differences in the number of leaves initiatedby the shoot apex prior to floral initiation, which in turnaffects the subsequent rate of development to ear emergenceand anthesis. Leaf primordia development during vernalizationand total leaf number at flowering were used to develop criteriato define both the progress and the point of saturation of thevernalization response. These criteria were then used to reinterpretthe results of Chujo ( Proceedings of the Crop Science Societyof Japan 35 : 177–186, 1966), and derive the temperatureresponse of vernalization per se for plants grown under saturatinglong day conditions. The rate of vernalization increased linearlywith temperature between 1 and 11 °C, such that the timetaken to saturate the vernalization response decreased from70 d at 1 °C to 40 d at 11 °C. The rate declined againat temperatures above 11 °C, and 18 °C was apparentlyineffective for vernalization. Total leaf number at saturation,however, increased consistently with temperature, as a resultof the balance between the concurrent processes of leaf primordiuminitiation and vernalization. Total leaf number at saturationincreased from 6 at 1 °C to 13.3 at 15 °C, which inturn influenced the time taken to reach ear emergence. The advantagesof using this developmental interpretation of vernalizationas the basis for a mechanistic model of the vernalization responsein wheat are discussed. Triticum aestivum L.; wheat; vernalization; rate; temperature; primordia; leaf number; flowering     

The Effect of Air Humidity on Photosynthesis of Ryegrass and White Clover at Three Temperatures

Increasing leaf-air vapour pressure deficit (VPD) decreasedthe stomatal conductance and the photosynthetic rate of leavesof ryegrass (Lolium perenne L.) and white clover (Trifolhimrepens L.) at light saturation and at lower irradiance. In ryegrassboth conductance and photosynthesis, and in clover photosynthesis,decreased less with increasing VPD in low irradiance than theydid at an irradiance which saturated photosynthesis. In ryegrass,relative to their values at 10 mb, photosynthesis and conductancedecreased less with increasing VPD at 25 °C than at 20 or16·5 °C. In white clover, relative conductance (butnot photosynthesis) was less reduced at 25 than at 16·5°C Measurements of VPD of air in the leaf canopy of a field-growncrop are combined with the observed responses of photosynthesisto VPD and temperature in a model. This shows that high VPDis likely to depress photosynthesis significantly and that,during a typical day, the rate of light saturated photosynthesismay remain fairly steady, because the depression of photosynthesisdue to rising VPD is offset by the stimulation due to risingtemperature Perennial ryegrass, Lolium perenne L., White clover, Trifolhim repens L., photosynthesis, leaf conductance, water vapour pressure deficit, temperature     

Modelling Optimal Temperature Acclimation of the Photosynthetic Apparatus in C3Plants with Respect to Nitrogen Use

A new hypothesis for temperature acclimation by the photosyntheticapparatus is presented. An optimization model is developed toexamined effects of changes in the organization of photosyntheticcomponents on leaf photosynthesis under various growth temperatureswhere the photosynthetic apparatus is not damaged. In this model,photosynthetic rate is limited either by the capacity of ribulosebisphosphate carboxylase (RuBPCase) to consume ribulose bisphosphate(RuBP), or by the capacity of RuBP regeneration. For temperaturedependence of the RuBPCase activity, data fromSpinacia oleraceaL.,which have a temperature optimum of 30 °C, are used. Fortemperature dependence of the capacity of RuBP regeneration,two contrasting curves that have temperature optima of 30 °C(Eucalyptus paucifloraSieb. ex Spreng) and 40 °C (LarreadivaricataCav.) are applied. The temperature dependence of eachprocess is fixed for respective species, but the rate of eachprocess varies with changes in the amounts of components. Thecost of proteins, in terms of nitrogen, required to carry outeach process is calculated when nitrogen is partitioned differentlyamong photosynthetic components. The optimal nitrogen partitioningthat maximizes daily photosynthesis at a given temperature isobtained. The predicted temperature optimum of the photosyntheticrate inLarrea divaricataexhibits large shifts with changes intarget temperature, while shifts are negligible inEucalyptuspauciflora. It is suggested that the shift in temperature optimumof photosynthetic rate is large when the temperature dependencesof the capacities of RuBPCase and RuBP regeneration differ fromeach other.Copyright 1997 Annals of Botany Company Optimization model; nitrogen use efficiency; photosynthetic acclimation; temperature dependence     

Leaf Extension in Zea mays: II. LEAF EXTENSION IN RESPONSE TO INDEPENDENT VARIATION OF THE TEMPERATURE OF THE APICAL MERISTEM, OF THE AIR AROUND THE LEAVES, AND OF THE ROOT-ZONE

The temperatures of the roots, the apical meristem, and theshoots of Zea mays plants were varied independently of eachother and the rates of leaf extension were measured. When thetemperature of the apical meristem and region of cell expansionat the base of the leaf was kept at 25 °C, changes of leafextension in response to changes of root and shoot temperatureswere less pronounced. When the temperature of the meristematicregion was changed by increments of 5 or 10 °C from 0 to40 °C, and the root and shoot temperatures were kept at25 °C, rapid changes in leaf extension occurred. It was concluded that the rates of leaf extension were controlledat root-zone temperatures of 5 to 35 °C by heating or coolingof the meristematic region. Changes in rates of leaf extensionin response to changes in air temperature were attributed todirect effects on the temperature of the meristematic regionand on the physiology of the leaf.     

Effect of Temperature on Growth of Crotalaria juncea L. and Crotalaria sericea Retz.

Growth performances of Crotalaria juncea L. and C. sericea Retz.have been compared at two controlled temperatures, 16–20°C, and 28–32 °C, with respect to increase ind. wt and leaf area, relative growth rate, leaf area ratio,specific leaf area, leaf weight ratio, net assimilation rate,the ratio of mean relative growth rate to mean relative rateof leaf area increase () and shoot/root ratios. Both the speciesgrew better at the higher temperature; however the relativegrowth rate was more affected by temperature in C. sericea thanin C. juncea. Further, it was observed to be more dependenton net assimilation rate than on the leaf area ratio. Crotalaria juncea L., Crotalaria sericea Retz., relative growth rate, leaf area ratio, specific leaf area, leaf weight ratio, leaf area increase, net assimilation rate, shoot/root ratio     

Primary Growth and Re-growth of the Tropical Tallgrass Hybrid Pennisetum at Different Temperatures

Dry weight of plant fractions, leaf area, leaf number and tillernumber were recorded throughout primary growth and two subsequentre-growths of hybrid Pennisetum (Pennisetum americanum x P.purpureum) at five temperature regimes from 15/10 °C to33/28 °C (day/night) in summer and winter. Seedling mortality occurred at 15/10 °C, whereas at allhigher temperatures seedlings survived and plants re-grew aftercutting at a height of 10 cm. Shoot weights increased with temperatureup to 33/28 °C when compared at a common chronological agebut showed no differences at a common developmental age. Thetemperature response was associated with increased top/rootratio and rate of leaf appearance; mean individual leaf areaand NAR did not increase beyond 27/22 °C. Shoot weight incrementsin primary growth were the same in winter and summer when expressedper unit of radiation, although leaf area per unit weight wassensitive to changes in radiation associated with differencesin daylength. The rate of shoot weight accumulation in regrowthwas greater than in primary growth because of rapid tilleringfollowing defoliation and an enhanced rate of leaf appearanceper tiller. Pennisetum hybrid, tallgrass, growth, regrowth temperature response     

An Analysis of the Effects of Temperature and Light Integral on the Vegetative Growth of Pansy cv. Universal Violet (Violaxwittrockiana Gams.)

Pansies (Viola xwittrockiana Gams.) cv. Universal Violet weresown on five dates between Jul. and Dec. 1992 and placed insix temperature-controlled glasshouse compartments set to providemean temperatures between 6.5 and 30 °C. Shoot dry weightand leaf number were recorded. A model was constructed, to analysethe effects of light and temperature on dry matter accumulation,which assumed that relative growth rate (RGR) declined linearlywith thermal time accumulated from sowing, reflecting ontogeneticdrift. Furthermore, it assumed that RGR was a semi-ellipsoidfunction of temperature, rising to an optimum of 25.3 °Cand declining thereafter, and a positive linear function oflight integral. When fitted to data collected in this studythe model accounted for 94% of the variance in RGR. Independentvalidation using data from four further crops grown in glasshousecompartments at four different set point temperatures showedthat the model could also be used to predict plant dry weightaccurately (r ²=0.98). The rate of mainstem leaf productionwas also linearly related to both light integral and temperature. Pansy; Viola xwittrockiana ; temperature; light integral; dry weight; relative growth rate; leaf number