Abstract
The objectives of this study are to investigate the bleeding rate of rice plants grow in a warmer region in south-west part of Japan during the growth period, and the relation between root activity and ripening were investigated. The bleeding rate of the rice plants (var. Hinohikari) grown under four different fertilizer application levels, were measured during the growth period in 3 years. The bleeding rate increased during the plant growth and reached a maximum value at 7 days before heading and decreased until the milk ripe stage. These results indicated that root activity of rice plants began to decrease before heading. The bleeding rate varied with the year and fertilizer application level, particularly with the year. The bleeding rate at the ripening stage did not significantly correlate to the yield of winnowed paddy, and increase in the dry matter and spike dry weight. However, the bleeding rate at 14 days after heading was significantly correlated with the percentage of ripened grain and the thousand grain weight. Thus, the bleeding rate could be used as an effective index in study on the effect of the activity of whole root system on ripening. The high root activity at milk ripe stage resulted in good ripening.
