Abstract
In order to determine the cause of pollen abortion in male-sterile Satsuma orange, certain morphological and cyto-histological studies with anthers were undertaken as compared with the male-fertile Buntan and Natsudaidai. Cyto-histological observations on Satsuma orange treated with temperature and IAA were also carried out.
1. In the early stage of anther development, meiosis and microspore formation were quite similar in fertile and sterile species of Citrus.
2. Tapetum in fertile species started to degenerate soon after the liberation of microspores from the wall of tetrads and almost completely degenerated during the disappearance of vacuoles from the cytoplasm of microspore.
3. Tapetum in sterile Satsuma orange occassionally showed an extraordinary development of large vacuole at the vacuole appearing stage and completely disintegrated at the vacuole enlarging stage of microspore. However, tapetum which remained cellular without large vacuoles persisted unusually long and degenerated at the vacuole enlarging stage of microspore. So it may be suggested that the tapetum in sterile Satsuma orange can not play normal nutritive role and supplies less nutrients to the developing pollens.
4. Abnormal behavior of tapetum in Satsuma orange could be recovered partially and the pollen fertility could be increased by temperature (at 20°C minimum temperature) and IAA treatments (500 ppm) to those plants growing under unfavorable temperature condition.
