抄録
These experiments were carried out to throw light upon a phenomenon of the increased sterility by top-dressing of excessive nitrogen at meiotic stage (hereinafter referred to as nitrogen treatment) in rice plants from the view of functions and structural characteristics of pollens as well as proline metabolism in anthers. It was found that the nitrogen treatment increased the sterility in both superior spikelets (spikelets of the 4th, 5th and 6th position on primary branches) and inferior ones (spikelets of the 2nd and 3rd position on secondary branches) to three times as much as control. On and after trinuclear period (III period), the content of proline in anthers was decreased conspicuously with nitrogen treatment, especially in the anthers of inferior spikelets in which the sterility reached about 40 percent. Morphological observations on the development of tapetum after nitrogen treatment indicated that there were no distinctive differences in behaviors of tapetum between control and treated anthers. In the late III period of pollen development, there were a lot of pollens without deformation of the vegetative nucleus and with a higher staining ability of the nucleoli by aceto-carmine in the treated anthers. These pollens were evidently smaller in diameter than the control. This supressed development was a consequence of the reduced growth rate of pollens in III period. Additionally, the nitrogen treatment also reduced the pollen germination. These results lead to the conclusion that the increased sterility of spikelets by nitrogen treatment belongs to the male sterility which may be caused by a disturbance of the developmental pattern of pollen at III period, when being under the control of two sperm nuclei.
