早魃が大豆の生育に与える影響特に開花に関して (予報)

抄録

In this experiment, it was tested how the flowering of soybean plants was influenced by the different contents of soil moisture, which were artificially kept 30% (A plot) and 70% (C plot) during the whole course of the growth and 30% during the flowering period (B plot). A local variety named Akazaya was used for this purpose. The results obtained were as follows : (1) The vegetative growth of plants grown under the drought conditions (A & B plots) was rather reduced in comparison to that of plants grown under normal (C plot) ; the decrement of numbers of both nodes and branches which bore flowers was striking in A plot. (2) Total number of flowers was therefore decreased by the treatments (A & B plots) : while it was found that the ratio of flowers in main stem to those in branches was always the same (1 : 3); notwithstanding those treatments. (3) The reduction of numbers of flowers in lower nodes was remarkable under the severest drought condition (A plot). Then the flowering in such a plant was found in nearly a rhomb shape In contrast to A plot, the shape was a triangle in normal plants (C plot). And in B plot, it took a middle shape between A and c . In short the reduction of flowers caused by the drought was due to that in lower nodes. (4) Days from the germination to the beginning of blooming were undistinguishable among three plots. But, under the constant drought condition (A plot), the blooming date seemed to be significantly postponed in both upper and lower nodes. (5) The duration of flowering period was reduced by the treatments ; especially the reduction occured evidently in upper and lower nodes of plants grown under the constant drought condition (A plot). (6) Concerning all stems examined, the influences of the treatments were almost unrecognizable in both sixth and seventh nodes. Because all flowers borne on these nodes were nearly the same in number in all plots.