关键词: 白桦, 雌花, 胚胎发育

Abstract: The development of female flower of Betula platyhylla and the processes of maturity of female organ should be undergoing approximately one month. Anatomic observation suggests as follows. In late April, primitive pistil began to undergo cell division and cell differentiation after dormancy. Ovary and stigma was growing at that time. Floral bloom and pollination happened respectively in the end of April and the beginning of May. After that and nucellus tissue ovules grew and differentiated integument from ovule in the middle May. Betula platyhylla has single integument, crassinucellate ovules which were anatropous. In the late of May, megasporocyte came into being and turn into embryo sac that has seven cells and eight nucleus in a week or so. Fertilization process finished in the end of May. Betula platyhylla embryo became mature after the process of zygote, proembryo, globular embryo, heart stage embryo and torpedo stage embryo. Meanwhile fertilized polar nucleus went into mitosis in Nuclear type. Endosperm increased and grew walls until heart stage embryo formed.

Key words: Betulla platyphylla, female flower, development of embryo