Grain Growth Dynamics in Winter Wheat Crops

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Abstract
A procedure for analysing the dynamics of grain growth is developed and applied to data from winter wheat crops. The algorithm estimates growth rate in relation to local data and preserves a shape through the whole growth curve by optimization subject to physiologically-justified constraints: that grain growth rate decreases monotonically, and that there is a discontinuity to zero rate at physiological maturity. It is assumed that effects of temperature can be allowed for by expressing growth in relation to thermal time, accumulated temperature above a base temperature. Conditions are derived under which an optimal base temperature for grain growth rate exists under these physiological constraints. When applied to data from crops with different sowing dates and nitrogen treatments in different years, weak optimal base temperatures of 2.0 and 7.5 °C were obtained for growth rate and duration, respectively. Initial growth rates were similar for all crops, but there were considerable variations in rate later in grain growth. These variations were, in part, related to the overall crop growth rate divided by the number of grains.

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