水稲冷害の実際的研究 : 第21報 障害型不稔籾の穂上分布について

抄録

With rice plants differing in the variety, cultural condition and growth year as materials, the authors investigated the distribution of sterile grains in a panicle caused by the low temperature in the developmental stage of young panicles and also cleared the relation between the frequency of occurrence of distribution types classified into six groups as shown in Table 1 and the sterile damage degree or the heading stage of the panicles investigated. 1. The sterility percentage of primary rachis-branches was found to be higher, in general, than that of secondary rachis-branches except for cases where damages were much smaller. 2. The frequency of occurrence of each distribution type was found closely related to the degree of sterile damage of the whole field as well as to the heading stage of panicles investigated: the distribution types in which sterile grains appeared more in the upper part of a panicle than in the middle and lower ones, namely, type I and II, were higher in the frequency in the case of heavier damage mainly due to earlier heading, while the types in which sterile grains appeared more in the lower part of a panicle, namely, type V and VI, were higher in the frequency in the case of smaller damage mainly due to later heading. 3. The cause of above phenomena is not known yet. It is presumed however from the past studies that they have a relationship, both direct and indirect, to two factors, namely, the developmental process of young panicles occurring in the period of an abnormal fall of the temperature and the difference in the order of differentiation and development among spikelets in a panicle.