Abstract
We made successive experiments on sodium uptake by two rice varieties, which were cultured on the different soils (grey lowland soils and wet andosols). 1) The strong negative correlation was observed between the amount of absorbed sodium not only at the final stage but also at the early growing stage of rice plants and the weight of abortive grain yield in spite of he different kinds of soils and rice varieties. 2) We considered that the depression of potassium uptake was caused by the low temperature of the irrigated water, and the nutriophysiological character of rice seedlings brought on the uptake of sodium in the early growing stage. 3) The substitute sodium absorbed during 35-45 days before the heading time for potassium brought about the decrease of abortive grain yield and the increase of percentage of ripened grains. 4) The absorbed sodium had the negative correlation for the weight of abortive grain and rice screenings, but it was positive for the percentage of ripened grains. In contrast to sodium, the absorbed potassium showed the negative correlation for these factors consisting yield. 5) Based on the above results, sodium and potassium are antagonistic to each other when they are absorbed into the rice plants, but we supposed they act independently of each other in the rice plant. 6) The amount of absorbed sodium was closely related to the limiting factor for the increase of brown rice yield.
