A Dynamic Equation for Plant Interaction and Application to Yield-density-time Relations

On p. 527 the legend for Table 2 should read: TABLE 2. Measured and simulated dry matter production (g m^–2)of Wimmera ryegrass. Data from Donald (1951) and sentence 7 in the text should read: Measured yields (averaged over four replicates and convertedto g m^–2), simulated yields and estimated parameters aregiven in Table 3. On p. 528 the legends for Tables 4 and 5 should read: TABLE 4. Measured and simulated dry matter production (g m^–2)of maize. Data from Tetio-Kagho and Gardner (1988) TABLE 5. Measured and simulated dry matter production (g m^–2)of lucerne. Data from Jarvis (1962), averages of four replicates,planted at two different dates in two successive years and sentence 1 should read: The maximum biomass production (A) of 113 g m^–2 of f.wt.corresponds with 6.3 g m^–2 of dry matter.     

Growth and Assimilate Conversion of Cotton Bolls (Gossypium hirsutum L.). 2. Influence of Temperature on Boll Maturation Period and Assimilate Conversion

A negative exponential relationship between temperature andboll maturation period (BMP), is hypothesized from publisheddata. A crucial experiment was undertaken to test this hypothesis.Six groups of cotton plants were placed under different temperatureregimes, half of these groups having a daily temperature amplitudeof 4 °C, the remainder of 10 °C. The resulting BMP valuesshowed good agreement with the hypothesis and a Q₁₀ of 2.46–2.56was calculated. Since the Q₁₀ for maintenance respiration isabout 2.2, the conversion efficiency of cotton bolls shouldincrease slightly with increasing temperature. However, themeasured increase of conversion efficiency with temperaturecannot be explained from reduced maintenance respiration aloneand this suggests a shift in boll composition as well. Bollswith a short BMP are produced at a lower cost per unit of maturedry matter than those having a long BMP.     

Growth and Assimilate Conversion of Cotton Bolls (Gossypium hirsutum L.) 1. Growth of Fruits: and Substrate Demand

A generalized growth pattern of cotton bolls and their componentsis derived from data available in the literature. This patternis used to calculate substrate requirements for dry matter accumulationand results in an estimated consumption of 138.5 g of (CH₂O)and 15.4 g of amino acids per 100 g of mature boll dry matteromitting maintenance respiration. For maintenance respirationat 12 h day and 12 h night temperature of 30 and 20 °C respectivelyand a boll maturation period of 50 days, 26.9 g CH₂O per 100g of mature bolls is found. The rate is considerably higherin the earlier phases of boll development when primarily ‘structuralgrowth’ occurs compared with later phases when ‘storagegrowth’ prevails.     

The Need for Simple Dynamic Equations to Describe Plant Competition

A dynamic single-equation model for plant interaction is comparedwith the competition mechanism implicit in larger simulationmodels. When light is the limiting factor, both mechanisms canbe written in the same mathematical form containing a ‘drivingforce’ and a restriction factor. In the single-equationmodel the driving force is derived directly from the RGR ofa competition-free plant. In more comprehensive models, detailedinformation on the growth of plant organs has to be generatedby submodels. When factors other than light are limiting growth, the representationof competition in crop simulation models is complex; the single-equationmodel has the same form irrespective of which factor is limitinggrowth. It is argued that simple dynamic models should be developedfor complex processes. Plant competition, dynamic model     

Leaf Growth in Cotton (Gossypium hirsutum L.) 1. Growth in Area of Main-stem and Sympodial Leaves

A model is presented for growth of individual and successivemain-stem leaves of cotton, based on a series of indoor experimentsand data sets from the literature. Three variable parametersare used to describe individual leaf growth: relative growthrate of meristematic tissue (R¹), relative rate of approachof final area (R₂) and a ‘position parameter’ (t_0.5)which governs the transition from meristematic to extensiongrowth. Final area of a leaf does not occur in the model asa deterministic quantity but it is a result of the processesduring growth. The model generates successive mainstem leavesand sympodial leaves as an integrated system. Assimilate shortagesoccurring in the plant operate on R₁ leading to the characteristicchange of final leaf area along the mainstem. Gossypium hirsutumL., cotton, leaf growth, relative growth rate, meristematic tissue, extension growth, mathematical model     

A Dynamic Equation for Plant Interaction and Application to Yield-density-time Relations

A model for plant interaction is developed based on a definitionof space in terms of actual and potential amount of growth factorsabsorbed per unit of time. The resulting equation is a second-orderdifferential equation which is solved by dynamic simulation.Five data sets on yield-density relations are used to demonstratethe model's excellent predictive power. Competition model, plant interaction, yield-density relations, Richards function, subterranean clover (Trifolium subterraneum L.), Wimmera ryegrass (Lolium loliaceum Hand-Mazz.), lettuce (Lactuca sativa L.), maize (Zea mays L.), lucerne (Medicago sativa L     

Leaf Growth in Cotton (Gossypium hirsutum L.) 2. The Influence of Temperature, Light, Water Stress and Root Restriction on the Growth and Initiation of Leaves

The rate parameters R₁, R₂, I/LI and I/t_0.5, which characterizethe growth in area of successive main-stem leaves, probablyall have the same temperature response. Temperature thereforeonly operates on the time scale. Water stress reduces both therelative growth rate and the advance of developmental age, thelatter however to a lesser extent than the former. The effectof root restriction is explained as resulting from mineral shortage. Gossypium hirsutum L., cotton, leaf growth, leaf initiation, relative growth rate, temperature, light, water stress, root restriction