栽培時期を異にする水稲の生育経過に関する研究 : I 水稲地上部の生育経過と稲体成分の推移について

抄録

In order to know the agronomical capability of rice plants in different season cultivation, such as early, usual and late, we investigated their growing progress and changes of chemical composition of them. 1) Rice plants cultivated early were lower in plant height, but more in number of tillers, that resulted more panicles per unit area as well as higher yield than those of the usual season cultivation. And the amount of growth and the yield was the least in late season cultivation (Fig. 1). 2) The increase of top-dry-weight in early cultivation was very small at the beginning but became larger at the end of growth period rather than that in usual cultivation. Dry weight of culm and leaves normally reached maximum around the time of heading and gradually decreased after-wards. Such decrease of dry weight was more conspicuous in the early cultivated rice-plants than in the other cases (Fig. 2). 3) Starch and total sugars percentage were determined in unit dry weight of sheath and internode. The figures were higher in early season rice plants than those in the other cultivation, especially during the earlier part of growth (Fig. 3). Therefore, in the early cultivation we must pay attention to lessen unavailable tillers and to make ears larger. Adversely in the late cultivation it is necessary to promote growth, and accelerate heading and ripening to get higher fertility.