Prediction and Measurement of the Decline in the Critical-K, the Maximum-K and Total Cation Plant Concentrations during the Growth of Field Vegetable Crops

The declines in maximum and critical K concentrations in plantdry matter of 16 different vegetable species were predictedfrom emergence to maturity by assuming that both were proportionalto the critical %N calculated in terms of plant dry matter perunit area using previously-described equations. Values of theproportionality constants were obtained from published measurementsmade, at commercial maturity, of crops grown in multi-levelfertilizer experiments. Predictions were tested: (a) againstmeasurements made at intervals during growth in experimentsreceiving a single level of fertilizer; (b) against measurementsmade of the highest K concentrations measured at the seedlingstage in soil-K gradient experiments; and (c) against the resultsof a K-fertilizer-response experiment in which harvests werecarried out at intervals during growth. Results were consistentwith the predictions and, thus, with the view that both criticaland maximum K concentrations are proportional to critical %Nthroughout growth. K concentrations in plant tissue water fluctuatedwidely during the growing season and values, averaged over theentire growing period for each of ten crops, varied by a factorof 3. These values were proportional to the mean cation concentrations(meq l^-1) calculated by assuming that all the ions were in solution.Total cation concentration (meq 100 g^-1) of dry matter was linearlyrelated to critical N concentration. Evidence was also obtainedthat maximum K concentration, critical K concentration and totalcation concentration (meq 100 g^-1) during growth were linearlyrelated to relative growth rate, provided that crop weightswere greater than 2 t ha^-1dry matter. A hypothesis was developedto co-ordinate these findings.Copyright 1998 Annals of BotanyCompany. Vegetable crops, cation, plant potassium, plant nitrogen, critical concentration, relative growth rate, plant weight.     

Mature Tissue and Crop Canopy Respiratory Characteristics of Rye, Triticale and Wheat

Crop dry matter and its chemical composition, together withcanopy and mature tissue respiration rates were measure at equivalentgrowth stages and temperatures for spring and winter rye, triticaleand wheat crops grown under irrigated field conditions. Canopyrespiration was partitioned into growth and maintenance respirationusing information from the chemical composition analysis ofthe crop biomass. Rates of dry matter accumulation early inthe growing season were significantly greater for rye cropsin comparison to triticale and wheat. However, when dry matterwas measured at similar ontogenetic stages, the productivityadvantage of the rye crop was no longer evident. Nevertheless,canopy respiration rates per unit ground area were significantlylower for rye than wheat over all temperatures and growth stages.Intergeneric differences in the respiration rates of matureleaf and stem tissues were consistent with those measured atcanopy scales. Differences in the chemical composition of thebiomass among genera were minimal, and insufficient to accountfor differences in canopy respiration due to synthesis respirationrequirement. Estimates of biomass maintenance requirements appearto be significantly lower for rye than wheat when calculatedat similar temperatures and ontogenetic stages. The maintenancecoefficient (m) depended on stage of development, suggestingthat m will decline earlier chronologically for rye than wheat,which implies that greater carbon retention is another aspectcontributing to the higher early-season crop growth rates ofspring and winter rye. Considering the lower respiration ratesof mature stems relative to leaves, the dependence of m on stem:leafratio was suggested as a useful approach to modelling ontogeneticeffects on maintenance respiration.Copyright 1993, 1999 AcademicPress Rye, triticale, wheat, dry matter, growth and maintenance respiration     

Dry Matter and Water Import Rates in the Tomato Fruit: a Model Incorporating the Changes in Sap Viscosity and Osmotic Potential with Temperature

The change in water import rate in tomato fruit was modelledby incorporating into a previously-published model the changesin sap viscosity and osmotic potential into fruit with temperature.An experimental relationship between water and dry matter importrates was used to compare the model to dry matter import ratesin fruit measured by Walker and Thornley (Annals of Botany 41:977-985, 1997) at different temperatures. The effect of temperatureon the water import rate, calculated from the model, was alsocompared with the effect of temperature on the fruit growthrate measured by Pearce, Grange and Hardwick (Journal of HorticulturalScience 68: 1-11 and 13-23, 1993). The model accounted for alarge part of these temperature effects. It was concluded that resistances in sap transfer pathways inthe tomato fruit could be due to viscosity. These results supported,on the one hand, the hypothesis that the progressive decreaseof water import rate during fruit growth could result partlyfrom the progressive increase in transfer pathway length, and,on the other hand, the hypothesis that the ratio between waterand dry matter import rates could depend on flow conditionsin transfer pathways. The equations of the model could be usedto simulate tomato fruit growth, mass and dry matter contentin relation to fruit size, to nutrient solution salinity andto fruit temperature.Copyright 1995, 1999 Academic Press Dry matter, fruit, growth, model, resistance, sap, temperature, tomato, transfer, viscosity, water     

A Dynamic Growth Model of Vegetative Soya Bean Plants: Model Structure and Behaviour under Varying Root Temperature and Nitrogen Concentration

A differential equation model of vegetative growth of the soyabean plant (Glycine max (L.) Merrill cv. ‘Ransom’)was developed to account for plant growth in a phytotron systemunder variation of root temperature and nitrogen concentrationin nutrient solution. The model was tested by comparing modeloutputs with data from four different experiments. Model predictionsagreed fairly well with measured plant performance over a widerange of root temperatures and over a range of nitrogen concentrationsin nutrient solution between 0.5 and 10.0 mmol in the phytotron environment. Sensitivity analyses revealedthat the model was most sensitive to changes in parameters relatingto carbohydrate concentration in the plant and nitrogen uptakerate. Key words: Glycine max (L.) Merrill, dry matter, nitrogen uptake, partitioning, photosynthesis, respiration, sensitivity analysis     

基于辐热积法模拟烤烟叶面积与烟叶干物质产量

烟叶叶面积增长与干物质累积是烤烟产量形成的主要部分,对品质的形成也有影响。本研究根据气温和光照对烤烟叶片生长和干物质累积的影响,基于辐热积理论建立了适用于不同烟区的烤烟叶面积模型和干物质累积模型,分别使用独立的试验数据建模及对模型进行检验,再通过多年次烟叶干重试验数据对模型进行检验。结果表明,与传统的预测方法相比,用辐热积模型获得的叶面积模拟值与实测值间1:1线的决定系数（R2）和RMSE值为0.9634和0.1653 m2/株,预测精度比SLA法和GDD法分别提高了93%和82%。模型对叶干重模拟的RMSE值为27.1 g/m2,用历年玉溪试验数据检验的RE值为24.5%,说明模型的拟合度和可靠性较好。本研究所建立的模型能够利用气温、日照等常规气象观测数据,动态预测烤烟叶面积增长和干物质累积,且模型参数少,符合度好,实用性强,可以为烤烟生产中的产量预测提供理论依据和决策支持。     

Growth Response of a Chrysanthemum Crop to the Environment. III, Effects of Radiation and Temperature on Dry Matter Partitioning and Photosynthesis

Vegetative crops of chrysanthemum were grown for 5 or 6 weekperiods in daylit assimilation chambers. Crop responses to differentradiation levels and temperatures were analysed into effectson dry matter partitioning, specific leaf area, leaf photosynthesisand canopy light interception. The percentage of newly formed dry matter partitioned to theleaves was almost constant, although with increasing radiationor decreasing temperature, a greater percentage of dry matterwas partitioned to stem tissue at the expense of root tissue.There was a positive correlation between the percentage of drymatter in shoot material and the overall carbon: dry matterratio. Canopy photosynthesis was analysed assuming identical behaviourfor all leaves in the crop. Leaf photochemical efficiency wasonly slightly affected by crop environment. The rate of grossphotosynthesis per unit leaf area at light saturation, P_A (max),increased with increasing radiation integral, but the same parameterexpressed per unit leaf dry matter, P_w (max) was almost unaffectedby growth radiation. In contrast, P_A (max) was hardly affectedby temperature but P_w (max) increased with increasing growthtemperature. This was because specific leaf area decreased withdecreasing temperature and increased with decreasing radiation.There was a positive correlation between canopy respirationintegral and photosynthesis integral, and despite a four-foldchange in crop mass during the experiments, the maintenancecomponent of canopy respiration remained small and constant. Canopy extinction coefficient showed no consistent variationwith radiation integral but was negatively correlated with temperature.This decrease in the efficiency of the canopy at interceptingradiation exactly cancelled the increase in specific carbonassimilation rate that occurred with increasing growth temperature,giving a growth rate depending solely on the incident lightlevel. Chrysanthemum, dry matter partitioning, photosynthesis, specific leaf area     

Analysis of Dry Matter Partitioning in Dactylis glomerata during Vegetative Growth Using a Carbon Budget Model

The dry matter partitioning in vegetative plants of Dactylisglomerata was studied from experiments performed in controlledenvironments. Plants were grown hydroponically in growth chambers,at two constant temperatures (17 and 25 °C). In both experimentsthe root fraction decreased regularly with time, an effect thatwas more accentuated in the higher temperature regime. In orderto explain the change in dry matter partitioning, the experimentalshoot and root growth were analysed using a carbon budget modelwhich includes shoot and root maintenance requirements. Themodel predicts a relationship between the root specific growthrate and the product of shoot specific growth rate and shootto root dry weight ratio. In the range of experimental accuracy,this relationship was found to be linear at both temperatures,which should indicate that the partitioning coefficients andthe root maintenance coefficient remained constant during vegetativegrowth. The effect of temperature on the value of these coefficientscan be specified from a linear regression analysis. Between17 and 25 °C, the root maintenance coefficient increasedby about a factor of two, whereas the partitioning coefficientsdid not vary significantly. On the basis of these results, itwas shown that the decrease in root fraction during vegetativegrowth should be mainly attributed to the decrease in net specificactivity of shoots.Copyright 1994, 1999 Academic Press Dactylis glomerata L., vegetative growth, model, partitioning, root:shoot ratio, shoot specific activity, maintenance requirements     

Dry Matter Production in a Tomato Crop: Measurements and Simulation

Simulation of dry matter production by the explanatory glasshousecrop growth model SUKAM (Gijzen, 1992, Simulation Monographs),based on SUCROS87 (Spitters, Van Keulen and Van Kraalingen,1989, Simulation and systems management in crop protection),was validated for tomato. In the model, assimilation rates arecalculated separately for shaded and sunlit leaf area at differentcumulative leaf area in the canopy, taking into account thedifferent interception of direct and diffuse components of light.Daily crop gross assimilation rate (P_gd) is computed by integrationof these rates over total crop leaf area and over the day. Leafphotochemical efficiency and potential gross assimilation rateat saturating light depend on temperature and CO₂ concentrationand are approximated as being identical in the whole canopy.Crop growth results from P_gd minus maintenance respiration rate(R_m; dependent on temperature and crop dry weight), multipliedby the conversion efficiency (carbohydrates to structural drymatter; C_f). Growth experiments (periodic destructive harvest) with differentplanting dates and plant densities and two data-sets from commerciallygrown crops, were used for model validation. Hourly averagesfor global radiation outside the glasshouse, glasshouse temperatureand CO₂ concentration, together with measured leaf area index,dry matter distribution (for calculation of C_f) and organ dryweights (for calculation of R_m) were the inputs to the model. Dry matter production (both level and dynamic behaviour) wassimulated reasonably well for most experiments, but final drymatter production was under-estimated by about 27% for the commerciallygrown crops. At low irradiance and with large crop dry weight,growth rate was under-estimated, probably as a result of over-estimationof R_m. This could almost completely explain the large under-estimationfor the commercially grown crops, which had large dry weight.Final dry matter production was over-estimated by 7-11% if dailyaverages instead of hourly input of climatic data were used. It is concluded that SUKAM is a reliable model for simulatingdry matter production in a tomato crop, except for those situationswhere R_m has a large influence on crop growth rate (low irradianceand large crop dry weight). An improved estimate of R_m wouldtake into account the influence of metabolic activity. A preliminaryattempt to relate maintenance costs to relative growth rate(a measure for metabolic activity), showed promising results.Copyright1995, 1999 Academic Press Crop growth, dry matter production, glasshouse, maintenance respiration, metabolic activity, model, relative growth rate, respiration, simulation, tomato, model validation     

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     

Potential Dry Matter and Water Import Rates in the Tomato Fruit in Relationship to Fruit Size

The tomato fruit was compared to a sphere with a radius R. Radialgrowth rates in the fruit (F_IW and F_ID) due to water importor to dry matter import, respectively, which are also the waterimport rate or dry matter import rate per unit surface areaof fruit, were calculated from two sets of published results.This data referred to fruits which swelled in such a way thatthe availability of assimilates had little effect on growth.Two varieties differentiated the two series of results and inone series, three trials were differentiated by the salinityof the nutrient solution. In all trials, it was found that F_IW and F_ID decreased whenR increased. Two phases were observed for F_IW: after a firstphase, F_IW decreased more quickly and almost linearly when Rincreased. F_ID was constant or decreased with respect to R.Except at the beginning of growth at the greatest salinity,there were clearly linear regressions between F_IW and F_ID suchas F_ID = aF_IW-b; where b was lower with higher salinity. Thechanges of the concentration of imported dry matter (F_ID/F_IWwere examined in terms of R and F_IW/R. The mechanisms controllingthe changes in F_IW and F_ID were discussed. The results suggestedfruit radius was an important parameter of these mechanisms.Thus, water import rate and dry matter import rate could eachbe considered to be the product of two factors: fruit surfacearea, which is directly dependent on fruit radius, and waterimport rate or dry matter import rate per unit of fruit surfacearea.Copyright 1993, 1999 Academic Press Dry matter, fruit growth, logistic model, sink size, tomato, water transfer     

A Coordination Model of Whole-plant Carbon Allocation in Relation to Water Stress

Although water is an important determinant of the allocationof material between roots and shoots during growth, and oftenparallels the effects of nitrogen, few models have explicitlyconsidered allocation in relation to water supply. We use coordinationtheory to develop a simple exponential model that considersallocation of dry matter between shoots and roots during growthin relation to carbon and watersupplies, and accounts for theeffects of water stress on growth. We compare coordinationvs.optimization(global and local) versions of the exponential model by examiningsimilarities and differences in model behaviour obtained underconstant and variable environmental conditions, and with drasticallychanging conditions (mild, moderate and severe water stress).The greatest differences between coordination and optimizationexist in the drastically changing conditions. In a second versionof the model, we remove the restriction of exponential growthand show how coordination principles can be extended to a morecomplicated structure. The non-exponential model is used toanalyse experimental data on the effects of different pot sizes(and hence water availability) on root restriction and plantgrowth as reported by Thomas and Strain (Plant Physiology96:627–634, 1991). With further refinements, the coordinationmodel has potential as a tool to model plant growth in relationto water supply under various environmental conditions. Optimization; functional balance; root: shoot ratio; root restriction     

The Vegetative Growth of Helianthus annuus and Phaseolus vulgaris as Affected by Seasonal Factors in Freetown, Sierra Leone

Sand-culture experiments were carried out in full daylight atsuccessive weekly intervals between March and December 1969,to investigate the effects of seasonal changes in climatic factorson the growth of Helianthus annuus and Phaseolus vulgaris inFreetown. Values for a number of growth parameters were calculatedfrom the dry weights of the leaves, stems, and roots, and fromthe leaf areas. Simultaneously the diurnal changes in climaticfactors were recorded. Multiple regressions linking light, temperature, and relativehumidity with some of the growth parameters were calculated.The total variance accounted for in the regressions of relativegrowth-rate, net assimilation rate, and leaf weight ratio onlight, temperature, and relative humidity ranged from 51 to60 per cent in P. vulgaris. In H. annuus relative humidity wasless important; the percentage proportion of total varianceaccounted for in the regression of leaf weight ratio (and leafarea ratio in both species) on light and temperature was notsignificant. The results showed that H. annuus grew faster than P. vulgaris,but the latter's growth was depressed less by the dull weatherof the rainy season. The relative growth-rates of both specieswere positively dependent on light and temperature while theirnet assimilation rates were negatively dependent on relativehumidity, and their leaf area ratios negatively dependent onlight. All parameters used except leaf area ratio and leaf areato leaf weight ratio showed seasonal variations correspondingto dry and rainy seasons. The initial and final values of leafarea ratio and weight ratios were always different but did notvary in the same direction in both species. The results are discussed in relation to similar work done elsewhere.     

Growth of Lettuce, Onion, and Red Beet. 1. Growth Analysis, Light Interception, and Radiation Use Efficiency

A field experiment was carried out to analyse the growth oflettuce, onion and red beet in terms of: (a) canopy architecture,radiation interception and absorption; (b) efficiency of conversionof absorbed radiation into biomass; and (c) dry matter partitioning.Growth analysis, total solar radiation interception, PAR interceptionand absorption by the crop canopy, ground cover, maintenancerespiration of onion bulbs and red beet storage roots were measured.Models for different leaf angle distribution and ground coverwere used to simulate light transmission by the crop canopy. The three crops are shown to have contrasting growth patternsfrom both a morphological and a physiological point of view.Lettuce showed very high light interception and growth afterthe early growth stages but, throughout the growth cycle, thisleafy crop showed the lowest radiation use efficiency due tothe respirational cost of the high leaf area. Onion showed alower early relative growth rate than lettuce and red beet.This was due partly to the low light interception per unit leafarea in the later stages of growth and partly to the low initialradiation use efficiency compared with the other two crops.On the other hand, thanks to more uniform distribution of theradiation inside the canopy, to the earlier termination of leafdevelopment and to the very low level of bulb respiration, onionshowed high radiation use efficiency and was able to producea large amount of dry matter. Red beet leaf posture and canopystructure resulted in high light interception and absorption.Its radiation use efficiency was lower than that of onion, partlyperhaps because of the more adverse distribution of the interceptedradiation fluxes within the canopy and partly because of thehigh respiration cost of a continuous dry-matter allocationto the leaves. However, this crop can accumulate a very largeamount of dry matter as leaf blade development and storage rootgrowth can both continue almost indefinitely, providing continuouslyavailable sinks. Ground cover gave a good estimate of the PAR interception onlyat low values of light interception but, in general, it underestimatedPAR interception in all three crops. Ratios between attenuationcoefficients established by considering PAR or total solar radiationand LAI or ground cover were calculated. Lettuce,Lactuca sativa L. var.crispa ; onion,Allium cepa L.; red beet; Beta vulgaris L. var.conditiva ; growth analysis; light interception and absorption; canopy architecture; ground cover; radiation use efficiency; maintenance respiration rate; dry matter distribution     

Effects of Low Temperature on Growth and Nutrient Accumulation in Rye (Secale cereale) and Wheat (Triticum aestivum)

Rye (Secale cereale cv. Rheidol) and wheat (Triticum aestivumcv. Mardler) were grown at shoot/root temperatures of 20/20°C (warm grown, WG plants), 8/8 °C (cold grown, CG plants)and 20/8 °C (differential grown, DG plants). Plants fromcontrasting growth temperature regimes were standardized andcompared using a developmental timescale based on accumulatedthermal time (°C d) at the shoot meristem. Accumulationof dry matter, nitrogen and potassium were exponential overthe time period studied (150–550 °C d). In rye, therates of plant dry matter and f. wt accumulation were linearlyrelated to the temperature of the shoot meristem. However, inwheat, although the rates of plant dry matter and f. wt accumulationwere temperature dependent, the linear relationship with shootmeristem temperature was weaker than in rye. The shoot/rootratio of rye was stable irrespective of growth temperature treatment,but the shoot/root ratio of wheat varied with growth temperaturetreatment. The shoot/root ratio of DG wheat was 50% greaterthan WG wheat. In both cereals, nutrient concentrations anddry matter content tended to be greater in organs exposed directlyto low temperatures. The mean specific absorption rates of nutrientswere calculated for the whole period studied for each species/temperaturecombination and were positively correlated with both plant shoot/rootratio and relative growth rate. The data suggest that nutrientuptake rates were influenced primarily by plant demand, withno indication of specific nutrient limitations at low temperatures. Nutrient accumulation, relative growth rate (RGR), rye, Secale cereale cv. Rheidol, temperature, thermal time, Triticum aestivum cv. Mardler, wheat     

Seasonal Periodicity in Germination of Seeds of Chenopodium album L.

Seeds of Chenopodium album L. were buried under field and controlledconditions. The germination capacity of these seeds was testedover a range of conditions at regular intervals. Seed buriedin the field only showed small seasonal changes in germinationcapacity when tested at constant temperatures in incubators.However, when germination was tested at field temperatures,seasonal changes in germination were more obvious. Nitrate andlight always promoted germination. There was a strong positiveinteraction between the effects of the two factors. When nitrateand light were combined, exhumed seeds germinated over a muchlonger period of the year than in water with or without light.Desiccation only stimulated under particular conditions, forexample, when germination was tested in nitrate in darkness.A regression model was developed with the data from the germinationtests in incubators. The model describes the changes in dormancyand germination and estimates germination at field temperaturesaccurately throughout the year. Despite the absence of clearseasonal changes in the temperatures suitable for germination(computed with the model), germination in the field showed seasonalperiodicity, because the field temperature and the germination-temperaturerange only overlapped from spring to late summer.Copyright 1993,1999 Academic Press Chenopodium album, lamb's quarters, dormancy pattern, germination, regression model, temperature, light, nitrate, desiccation     

A Simulation Model for Dry Matter Partitioning in Cucumber

A dynamic model is developed for the simulation of the dailydry matter distribution between the generative and vegetativeplant parts and the distribution among individual fruits ingreenhouse cucumber. The model is based on the hypothesis thatdry matter partitioning is regulated by the sink strengths ofthe plant organs. The sink strength of an organ is defined hereas its potential growth rate, i.e. the growth rate at non-limitingassimilate supply. The sink strength of each individual fruitis described as a function of its temperature sum after anthesisand the actual temperature, that of the vegetative plant partsas a function of actual temperature only. The formation rateof non-aborting fruits is essentially a function of the source/sinkratio. Model results agreed well with the measured fluctuating distributionof dry matter between fruits and vegetative parts. The measuredeffects of three intensities of fruit removal were also simulatedsatisfactorily. When simulating the partitioning among individualfruits the final fruit size was simulated quite well. However,the growth rate of young fruits was usually overestimated andthat of old fruits underestimated, because of dominance amongfruits. This phenomenon could be accounted for by incorporatingpriority functions into the model. Finally, a sensitivity analysisof the model was performed to investigate the effects of someclimatic factors, manipulations of the number of fruits on aplant and model parameters on dry matter distribution. Strategiesto manipulate the dry matter distribution are discussed.Copyright1994, 1999 Academic Press Cucumber, Cucumis sativus (L.), dry matter distribution, fruit growth, partitioning, simulation model, source-sink     

Differential Inhibition of Shootvs.Root Growth at Low Temperature and its Relationship with Carbohydrate Accumulation in Different Wheat Cultivars

Shoot and root growth rate, carbohydrate accumulation (includingfructan), reducing sugar content and dry matter percentage weremeasured in six wheat cultivars, ranging from winter to springtypes, grown at either 5 or 25 °C. At 5 °C (comparedwith 25 °C), the relative growth rate (RGR) of shoots wassimilarly reduced in all cultivars, but the RGR of shoots wasmore affected in winter wheats. This difference resulted insmaller root:shoot ratios than in spring wheats, which alsodeveloped more first-order lateral roots. A direct relationshipbetween carbohydrate accumulation at low temperatures and reductionin root growth was established. These results suggest that differentialshootvs.root growth inhibition at low temperature may play akey role in carbohydrate accumulation at chilling temperatures.This differential response might lead to improvements in survivalat temperatures below 0 °C, regrowth during spring, andwater and nutrient absorption at low temperatures.Copyright1997 Annals of Botany Company Wheat; Triticum aestivum; low temperatures; root growth; root: shoot ratio; sugar accumulation     

Evaluation of a Dynamic Simulation Model for Tomato Crop Growth and Development

A dynamic simulation model for tomato crop growth and development,TOMSIM, is evaluated. Potential crop growth and daily crop grossassimilation rate (P_gc,d) is computed by integration of leafassimilation rates over total crop leaf area throughout theday. Crop growth results fromP_gc,dminus maintenance respirationrate (R_m), multiplied by the conversion efficiency. Dry matterdistribution is simulated, based on the sink strength of theplant organs, which is quantified by their potential growthrate. Within the plant, individual fruit trusses and vegetativeunits (three leaves and stem internodes between two trusses)are distinguished. Sink strength of a truss or a vegetativeunit is described as a function of its developmental stage.In this paper, emphasis is on the interactions between the twosubmodels of, respectively, dry matter production and dry matterdistribution. Sensitivity analysis showed that global radiation,CO₂concentration, specific leaf area (SLA) and the developmentalstage of a vegetative unit at leaf pruning had a large influenceon crop growth rate, whereas temperature, number of fruits pertruss, sink strength of a vegetative unit and plant densitywere less important. Leaf area index (LAI) was very sensitiveto SLA and the developmental stage of a vegetative unit at leafpruning. Temperature did not influence the simulated R_m, asincreased respiration rate per unit of biomass at higher temperatureswas compensated by a decrease in biomass. The model was validatedfor four glasshouse experiments with plant density and fruitpruning treatments, and on data from two commercially growncrops. In general, measured and simulated crop growth ratesfrom 1 month after planting onwards agreed reasonably well,average overestimation being 12%. However, crop growth ratesin the first month after planting were overestimated by 52%on average. Final crop dry mass was overestimated by 0–31%,due to inaccurate simulation of LAI, resulting partly from inaccurateSLA prediction, which is especially important at low plant densityand in a young crop.Copyright 1999 Annals of Botany Company Crop growth, dry matter production, glasshouse, leaf area,Lycopersicon esculentum, partitioning, simulation model, tomato, TOMSIM.     

A Comparison of the Growth of the C4 Grass Spartina anglica with the C3 Grass Lolium perenne at Different Temperatures

Dunn, R., Thomas, S. M., Keys, A. J. and Long, S. P. 1987. Acomparison of the growth of the C₄ grass Spartina anglica withthe C₃ grass Lolium perenne at different temperatures.—J.exp. Bot. 38: 433–441. S. anglica is one of the few C₄ species which occurs naturallyin cool temperate zones. It is known to attain photosyntheticrates which equal or exceed those of C₃ grasses over the temperaturerange typical of the spring and summer in cool temperate climates.This study examines whether S. anglica can also attain comparablegrowth rates at these temperatures. Seedlings of S. anglicaand L. perenne cv. S23 were grown in controlled environmentsat 10,15,20 and 25 °C. Quantitative growth analysis wasconducted by taking frequent harvests to determine the progressionsof leaf area and plant weight of individual plants with time.Quadratic regressions were found to describe these progressionswell. Instantaneous derived growth parameters were calculatedfrom the fitted regressions. Both absolute and relative growthrates of S. anglica were significantly lower than for L. perenne,this being largely attributable to a lower ratio of leaf areaproduction per unit of plant dry weight. Although the amountof dry matter invested into leaves was similar, the leaf areaper unit of leaf dry weight was lower in S. anglica. In comparisonto L. perenne, the rate of dry matter accumulation per unitof leaf area (ULR) was higher in S. anglica at 25 °C andinitially equal at 10 °C. Prolonged exposure to 10 °Csteadily reduced ULR in S. anglica which approached zero at80 d. Although growth in S. anglica is reduced more by low temperaturethan it is in L. perenne, by comparison to other C₄ speciesthe assimilatory capacity of S. anglica is more tolerant oflow temperature exposure. Key words: C4 photosynthesis, temperature, quantitative growth analysis     

The Effect of Temperature on Growth, Oil Yield and Oil Quality of Japanese Mint

Field studies of factors affecting yield and composition ofJapanese mint oil are confounded by interacting environmentalagencies. The effect of temperature, separated from other influences,was examined on Japanese mint (Mentha arvensis L. var. piperascensHolmes) in the naturally lit controlled environment Phytotron,Canberra, Australia. The So Wo I variety of Japanese mint wasgrown under 12 treatments consisting of four day and three nighttemperatures. Maximum leaf, stem and root dry matter was producedunder 30 °C day temperatures, regardless of night temperature,but maximum stolon growth occurred at 20 °C temperatures.Generally, oil yield could be estimated by determining dry matterof above ground parts, but number of oil glands on the leavesdid not provide a reliable indication of oil yield. Differenttemperature treatments did not appear to affect greatly thepercentage of menthol, an important component of the oil. Underfield conditions, maximum yield of Japanese mint oil has beenfound to occur during flowering. This close relationship betweenoil yield and flowering did not occur under extremes of temperature.Although 30 °C was found to be the optimum day temperaturefor oil yield in this experiment where only one harvest wasmade, it is possible that where multiple harvests are conducted,a lower optimum temperature might be found, since the highertemperature was detrimental to dry matter reserves in the stolons. Mentha arvensis L. var. piperascens Holmes, Japanese mint, temperature, controlled environment, menthol, methone, essential oil, flowering