Some Considerations upon the Reason of Increase of Panicles in Number, in Early Season Cultivation of Paddy Rice

1) We had already observed the fact that the early season rice culture gave higher yield than the usual, and ascribed the reason mainly to the larger number of panicles per unit area in the former, after analysing the relation of yielding factors. 2) Rice plant grown in early season had more available tillers on the main stem, as the lower nodes bear tillers, thus enlarging the tillering zone on the stems (Fig. 1). This was true with different growing-types. 3) At both stages, when the number of available tillers was determined and when the number of tillers came to the maximum, each stalk of early season rice plant was smaller in size, but the content was quite different, the total sugars and starch percentage and the quantity per one stalk being higher than usual (Fig. 5). We supposed such fact might be attributable to the higher productivity of early season rice. 4) The result of investigation showed tolerable correlation (-) between plant height and the number of stalks per unit area among the date from many different districts in Japan (Fig. 4). The growth form ……Shorter stalks and more tillers……was generally observed in early season cultivation as well as cooler-region cultivation (Fig. 2). We have also ascertained the same phenomenon in early season, comparing between the out-door growth (lower temp.) and the glass-house growth (higher temp.) of rice plants (Fig. 3). 5) The conclusion was that the lower temperature must be favourable for tillering, rather than higher in natural circumstances, and might be beneficical for increasing the number of panicles of rice plant, thus resulting the higher yield.