カキ‘西村早生’の胚嚢の発育に関する研究

Abstract

Japanese persimmon cv. ‘Nishimurawase’ is a pollination variant non-astringent(PVNA) type, and de-astringency has not been achieved along with decreased capability of seed formation.This decreased capability has been researched from the point of view of male gamete sterility, germination percentage and germination rate of pollen, previously. In this paper, the development of embryosac from the mother cell to complete formation was investigated in order to understand the relationship between capability of seed formatiom and female sterility. Embryosac mother cells and tetrasporangii were formed 18 and 12 days before bloom. The embryosac reached maturity 4 days before bloom. There were 3 phases in the development: the first phase, characterized by extension and no enlargement, extended from embryosac mother cell to tetrasporangium, the second phase, characterized by rapid enlargement, extended to the nuclear division of embryosac cells, and the third phase, characterized by rapid extension, extended to completion of the embryosac. Embryosac abortion and degeneration were observed, at rates reaching 22.5%, after the tetrasporangium or embryosac cell formation phases. There might be only six fertile embryosacs in a ‘Nishimurawase’ fruit judging from the percentage of embryosc abortions and degenerations.