Relationship Between Grain Growth and Postanthesis Leaf Area Duration in Dwarf, Semidwarf and Tall Isogenic Lines of Wheat

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Abstract
Experiments were carried out during 1992 and 1993 growing seasons using in the former year 2 (an early and late) sowing dates. Plants of three isogenic lines (standard height, semidwarf and dwarf) of wheat were grown under field conditions with no restrictions on water or nutrient availability with the objective of determining whether differences in rate of grain growth and in final grain weight were related To differences in leaf area duration postanthesis (LAD). A logistic and an optimization model were used to estimate the components of final grain weight and their performances were compared. The optimization model appeared more appropriate than the logistic to estimate final grain weight and their components (i.e. rate of grain growth and duration of grain filling).The dwarf line presented the lowest average grain weight followed by the semidwarf and standard height lines, respectively. However, changes in grain weight due to the action of Rht alleles were independent of the I, AD, suggesting that reductions in grain weight due to delayed sowing date could be associated with a direct effect of temperature on grain development.Changes in final grain weight were associated with changes in rate of grain growth, but nor with duration of the grain filling period, demonstrating that rate of grain growth was the main factor responsible for final grain weight.