一、明确被子植物生殖细胞的形成过程1.卵细胞和极核的形成过程雌蕊的大孢子母细胞经过1次减数分裂形成4个大孢子,其中3个退化消失,剩余的1个大孢子发育成单核胚囊,再经过3次有丝分裂形成8个细胞核的胚囊,即1个卵细胞、2个极核、3个助细胞和2个反足细胞。所以卵细胞和极核是同源的,其中的染色体数都是体细胞的一半,且基因组成也一样。其形成过程可表示为: 1. The formation process of germ cells in angiosperms 1. The process of formation of oocytes and polar nuclei The megaspore mother cells of the pistil are subjected to 1 meiosis to form 4 megaspores, of which 3 are degenerated and the remaining 1 megaspore develops. Into the mononuclear embryo sac, after three mitotic divisions, 8 nuclei of embryonic sac were formed, ie, one oocyte, two polar nuclei, three synergids, and two antipodal cells. So the egg cell and the polar nucleus are homologous, and the chromosome number is half of the somatic cell, and the genetic composition is the same. The formation process can be expressed as: