Characteristics of Grain Development in Wheat Compared with Rice

Abstract

The grain growth patterns per area and within each inflorescence (panicle or spike) were examined in rice and wheat. Panicle weight increased significantly, and the stem plus leaf weight decreased significantly 5 to 20 days after flowering in rice. Spike weight increased significantly 10 to 30 days after flowering and the stem plus leaf weight decreased significantly 20 to 30 days after flowering in wheat. The grain weight at 20 days after flowering (early grain weight), the grain weight at maturity (mature grain weight), and the difference between them (late grain weight) were measured according to the position within each inflorescence. In rice, the superior grains showed a considerably heavier early grain weight and a slightly lighter late grain weight, resulting in a slightly heavier mature grain weight, compared with the inferior grains. In wheat, the superior grains showed heavier early and late grain weights, resulting in heavier mature grain weight. In rice, in spite of the increase in the panicle weight and preferential enlargement of superior grains during the early ripening period, the variation in mature grain weight within a panicle became small since the enlargement of superior grains was restricted by the husk. In wheat, the increase in the spike weight and the preferential enlargement of superior grains during the late ripening period resulted in the large variation in mature grain weight within a spike.