INFLUENCE OF EMBRYO-SAC DEVELOPMENT AND F ERTILIZATION PROCESSES ON SEED FORMATION OF JAPANESE PERSIMMON (DIOSPYROS-KAKI L F) CV FUYU

Embryo-sac development and fertilization processes of Japanese persimm on (Diospyros kaki L. f.) cv. Fuyu were histologically investigated to clarify the cause of variations in seed formation among the trees. 1. The embryo-sac was formed after meiotic division of the embryo mother cell about 2 weeks before anthesis. One nucleus in the embryo-sac div ided into 8 nuclei and the embryo-sac was completed after the antipoda l cell disappeared. 2. Abnormal embryo-sac formation was observed : a) presence of a nucellus but lacking an embryo-sac, b) multiplied embry o-sacs, c) aborted embryo-sacs, and d) embryo-sacs with more or less t han normal 8 nuclei. 3. Pollen tubes reached the micropyles 24 or more hours after pollination, but their numbers were few. 4. Most fertiliz ation of eggs occurred 3 days after anthesis. Without zygote formation embryo-sacs began to degenerate in about 7 days, followed by-the inne r walls of the nucellus fusing together. 5. On vigorous shoots. meioti c division of the embryo-sac mother cell began earlier and the develop ment of the embryo-sacs was faster than on less vigorous shoots. Howev er, there were no differences in the percentage of abnormal embryo-sac s at anthesis and seed numbers per fruit on shoots of different length s. 6. The percentage of abnormal embryo-sacs was low in the tree which produced many seeds per fruit and, conversely, it was high in the tre e which produced a few seeds per fruit. We conclude that the variation s in seed formation among the trees probably resulted from their diffe rence in the frequency of abnormal embryo-sacs.