(5(1-2):17-30)Studies on the Development of Embryosac and Pollen Grain in Tetraploid Rice

1．本研究係觀察四元體稻之胚囊，與花粉粒之發生以及考察胚囊與花粉粒發生之異常對植物不稔性之關係等。 2．四元體稻胚囊發生之異常均於一核期以後開始，共後隨時期之進行，異常之頻度亦漸增加。 3．成熱期之胚囊有各種異常型，而共異常程度順著者概發生於初期，輕微者概發生於後期。 4．成熟期之異常胚囊比率在本研究所用之同源四元體稻內約爲2/5，較不稔率爲低。 5．花粉粒之退化均發生於比較後期，卽於第二收縮期以後，始能看相清楚，其正常花粉率較結實率爲高。 1. The present paper dea1s with the development of embryosac and pollen grain in tetraploid rice which was observed in order to gain information on the cause of sterility of tetraploid rice. 2. Deterioration was found to become visible at one nucleus stage (after the collapse of outer three cells of an embryosac tetrad) and seemed to increase with the progress of stage. 3 At the time of maturation. different types of irregularities were found ranging from such that the embryosac cavity was filled by nucellar cells to nearly normal ones. The higher the degree of change. the earlier the stage of beginning of deterioration. 4 At the time of heading, abnormal embryosacs were found in about 2/5 of those observed. This ratio is much lower than the percentage of steri'e seed. Since the assortment of chromosomes seems to be numerically normal in a greater part of cells, the sterility in tetraploid plaits may be due maigldy to some physical disturbances. 5. In the course of microsporogenesis, degeneration of pollen grain was found to increase after the second contraction stage. Good pollen percentage was higher than the percentage of fertile seed