Abstract
Bleeding sap rate was monitored to evaluate physiological activity of whole root systems in field-grown rice plants on the condition that bleeding sap rate will be determined by the combination of the total root length and its physiological activity. Bleeding sap rate of rice plants increased to reach the maximum at the heading stage mainly because of increase in root length, and thereafter rapidly decreased during the grain-filling period due to no new root formation. Examination on bleeding sap rate in relation to yield showed the importance of slower senescence of root system to get higher yield. Analysis on nitrogen in bleeding sap can be examined on the condition that nitrogen uptake will be determined by the combination of nitrogen concentration and bleeding sap rate. Such considerations will be helpful to increase yield through improving root system activity.
