Abstract
The present studies were conducted to clarify the effects of high temperature (50°C)treatment to unhulled rice seeds for seven days on the germinability and initial growth of seedlings. The author used 26 new and old cultivars which possessed different degrees of germinability in Hokkaido. The results obtained were summarized as follows: 1. A highly significant correlation existed between the germination coefficients of treated seeds and that of untreated seeds, and the order of the germinability in the cultivars was not affected. 2. Though the heat treatment decreased the germination coefficients by 8% in the mean value of the cultivars, the values of germination coefficient varied depending on individual cultivars. Namely, the coefficients of thirteen cultivars increased, while the others decreased in various degrees. 3. The rate of fluctuation in the germinability caused by the treatment was expressed as a following formula: [numerical formula] The negative and strong correlation was recognized between germination coefficients in the treated and the rate of fluctuation. The treatment improved the degree of germinability in the cultivars of the low germinability. 4. The initial growth of seedlings expressed with plant height and number of roots was inhibited by the treatment in most of cultivars. The correlation between germination coefficients and initial growth of seedlings in the treated group was lessened by the treatment. 5. From the mentioned above, the heat treatment was effective to increase germination coefficients of the promising cultivars possessing a weak degree of germinability.
