银杏雄配子体发生发育过程中的细胞分裂

Cell Divisions During Microsporogenesis and Development of the Male Gametophyte in Ginkgo biloba 

银杏（ＧｉｎｋｇｏｂｉｌｏｂａＬ．）小孢子母细胞减数分裂中，拟核经过规律性的变化后，初步建立了由近极面到远极面间的轴向极性，因而，雄配子体萌发时的３次分裂都是典型的极性平周分裂；这些极性平周分裂很可能是对原有极性的进一步加强；在结构上，各子细胞间的细胞壁缺少胞间连丝，因而，这些细胞壁可能起着使子细胞孤立化的作用，从而完成雄配子体中各细胞间的精细分化。生殖细胞的分裂很可能是斜背式环形分裂（ａｎｔｉｃｌｉｎａｌｒｉｎｇｌｉｋｅｄｉｖｉｓｉｏｎ），这种分裂可能是对最初极性方向的重大调整。结果，精原细胞的分裂方向为垂周分裂，产生两个背靠背排列的精子。

During meiosis of the microsporocyte of Ginkgo biloba L., the nucleoids, after going through a series of regular dynamic changes, had primarily established an axial polarity from the proximal face to the distal face of the cell. In the consequent germination, the microspore went through three consecutive polar periclinal mitotic divisions, which may be considered as further intensifying the primary polarity. In terms of structural change, lacking of plasmodesmas in the walls between the daughter cells, may set forth in isolating all the daughter cells in which fine differentiation took place. The anticlinal ring like division observed in the generative cell might play an important role in polarity regulation in the male gametophyte, eventually leading to the anticlinal division in the spermatogenous cell to produce two back_to_back positioned spermatozoids.