Relation between bleeding rate of rice and yield component in the south-western part of Japan

It is essential to clarify the relation between root activity and yield component to improve rice ripening in the southwestern part of Japan. Therefore, bleeding rates of rice plants (cv. Hinohikari) grown under four different fertilizer application levels were investigated during growth period. The result showed that their root systems developed differently depending on fertilizer levels. The differences among the functions of the root systems were also observed. The maximum value of bleeding rate was shown at about 10days before heading for all fertilizer levels. There was a significant correlation between the bleeding rate at meiotic division stage and the number of spikelets per panicle. A highly positive correlation was also found between the bleeding rate and the percentage of ripened grain. These conclude that maintaining of root functions after heading stage is important to improve the percentage of ripened grain as well as to increase the yield of rice.