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    ABSTRACT: One of the critical traits of rice ideotypes with an increased yield potential is the length of the period from sowing to flowering. The objective of this study was to optimize preflowering phenology of irrigated rice (a L.) for hig L.) for high yield potential in different Asian environments. A well-evaluated ecophysiological model for irrigated rice production, ORYZA1, was used in this study. This model was coupled to the 3s-Beta model for preflowering phenology that accounts for critical changes in photothermal responses of rice during ontogeny. Using a random number generator programme, 808 combinations of parameter values of the 3s-Beta model, each equivalent to a hypothetical plant type, were created. The yield potential of these plant types was estimated by ORYZA1 for three locations, representing tropical, subtropical and temperate climatic environments, respectively. For each environment there was an optimal preflowering period (PFP) that produced the highest yield. That PFP was not suitable in the subtropical and tropical environments from a cropping system viewpoint, however. In the subtropical environment, rice yield potential was restricted by the available growing season. In the tropical location, a critical flowering time was found, beyond which yield did not increase much by extending PFP. This critical value can be determined as the practically optimum PFP for the location as it allows a minimum growth duration without sacrificing yield potential. Yield was not sensitive to changes in individual phenological characteristics at the same PFP. As current standard cultivars in the different environments have a PFP that is very close to the optimum, the possibility for further improvement of yield potential by manipulating preflowering phenology is limited.
    Field Crops Research 03/1997; DOI:10.1016/S0378-4290(96)01043-X · 2.61 Impact Factor
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    ABSTRACT: Descriptive and explanatory modelling of biomass production and yield of horticultural crops is reviewed with special reference to the simulation of leaf area, light interception, dry matter (DM) production, DM partitioning and DM content. Most models for prediction of harvest date (timing of production) are descriptive. For DM production many descriptive and explanatory models have been developed. Most explanatory models are photosynthesis-based models. Important components of photosynthesis-based models are leaf area development, light interception, photosynthesis and respiration. Leaf area is predominantly simulated as a function of plant developmental stage or of simulated leaf dry weight. Crop photosynthesis can be calculated as a function of intercepted radiation or more accurately by considering radiation absorption of different leaf layers in combination with a submodel for leaf photosynthesis. In most crop growth models respiration is subdivided into two components: growth and maintenance. There is reasonable consensus concerning the simulation of growth respiration, but the simulation of maintenance respiration is still an area of great uncertainty, which is especially important for large crops grown under winter conditions at relatively high greenhouse temperatures. DM partitioning can be simulated by descriptive allometry, functional equilibrium or sink regulation. The most suitable approach depends on the type of crop studied and the aim of the model. As opposed to most agricultural crops, the DM content of the harvestable product is of great importance to the yield of most horticultural crops. More attention should be paid to the simulation of DM content. It is concluded that the strong features of explanatory crop growth models are the simulation of light interception and gross photosynthesis, while the weak features are the simulation of leaf area development, maintenance respiration, organ abortion, DM content and product quality.
    Scientia Horticulturae 04/1998; DOI:10.1016/S0304-4238(98)00083-1 · 1.50 Impact Factor
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    ABSTRACT: Photosynthetic capacity was measured on detached leaves sampled in a canopy of Solidago altissima L. Non-rectangular hyperbola fitted the light response curve of photosynthesis and significant correlations were observed between leaf nitrogen per unit area and four parameters which characterize the light-response curve. Using regressions of the parameters on leaf nitrogen, a model of leaf photosynthesis was constructed which gave the relationships between leaf nitrogen, photon flux density (PFD) and photosynthesis. Curvilinear relations were obtained between leaf nitrogen and photosynthetic rate on both an instantaneous and a daily basis. Nitrogen use efficiency (NUE, photosynthesis per unit leaf nitrogen) was calculated against leaf nitrogen under varying PFDs. The optimum nitrogen content per unit leaf area that maximizes NUE shifted to higher values with increasing PFD. Field measurements of PFD showed high positive correlations between the distribution of leaf nitrogen in the canopy and relative PFD. The predicted optimum leaf nitrogen content for each level in the canopy, to achieve maximized NUE during a clear day, was close to the actual nitrogen distribution as found through sampling.
    Physiologia Plantarum 04/2006; 70(2):215 - 222. DOI:10.1111/j.1399-3054.1987.tb06134.x · 3.26 Impact Factor

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