Relation between the Tolerance to the Sterility Type of Cool Injury and the Amount of Bleednig Water in Rice Plants

Abstract

Studies were conducted to clarify the relationship between the root activity and the tolerance to the sterility type of cool injury in rice, Oryza sativa L. Several varieties were selected on the basis of variations in their tolerance to the steril;ty type of cool injury. The amount of bleeding water from the stem was measured under different temperature conditions in the late vegetative growth stage. It was found that the amount of blcedlng water per stem section area varied with the temperature conditions ; the higher the temperature, the larger the amount was. It was also found that the amount of bleeding water per stem section area under the 10w temperature condition was highly correlated with the degree of tolerance to the sterility type of cool injury of the varieties. Furthermore, to measure the amount of bleeding water more easily, the shoot of a main stem was cut at the hight of 10cm above the ground, and the roots were washed off with running water. The main stem arranged in this way was fixed in a test tube by a piece of cotton. By measuring the amount of water lost in the test tube which was almost equivalent to the amount of bleeding water under the low temperature condition, it was found that the amount of water lost per dry matter weight of treated roots was closely related to the degree of tolerance to the sterility type of cool injury of the varieties. These results suggest that the degree of tolerance to the sterility type of cool injury of the varieties can be tested by measuring the amount of bleeding water in the late vegetative growth stage.