Differentiation of the male nucleus receptor apparatus on the female nucleus of the gymnosperms.

本文对苏铁和银杏两种裸子植物雄性核感受器的发育和分化进行了研究。在受精过程中，该器官起着接受雄性核的特殊受体的作用，也是配子束核融合的场所。它是核膜的凹陷，核膜上有许多细小的模糊折叠。在苏铁的卵核中，该器首先在其外侧分化，即核向细胞中心迁移的方向。最后位于卵核的前部，与颈卵器的颈细胞相对。精子和卵细胞融合后，雄核在卵子细胞质中向雌核迁移，并容纳在雌核的凹陷中。在两种生殖细胞融合后雄核向雌核迁移的过程中，银杏生殖器发生分化。这两种植物雌核的行为差异可能受卵细胞大小不同的影响；苏铁的雌核非常大，直径超过2毫米，宽1-1.5毫米，直径约350微米。因此，卵母细胞胞质内的核迁移距离在前者明显较长，而在后者较短。根据卵细胞大小和配子核融合方式的比较，松科植物中可能形成相同结构的卵细胞。

In this study the developmetnt and differentiation of the male nucleus receptor apparatus were investigated in two gymnosperms, Cycas revoluta and Ginkgo biloba. The apparatus functions as a specialized receptor for the acceptance of the male nucleus and as a site of fusion of the gametangial nuclei during fertilization. It is a depression of the nuclear envelope which is frilled with many fine fuzzy foldings of the nuclear membrane. In the egg nucleus of Cycas the apparatus firstly differentiate at its lateral side with regard to the direction of nuclear migrrtion towards the cell center. Finally it locates at the anterior region of egg nucleus facing the neck cells of the archegonium. After fusion of the sperm and egg cells the male nucleus migrates towards the female nucleus in the egg cytoplasm and is accomodated into depression of the female nucleus. The apparatus of G.biloba differentiates during the migration of male nucleus toward the female nucleus after fusion of both reproductive cells. The difference of behavior of the apparatus in these two plants is probably effected by different sizes of egg cells ; the female nucleus of Cycas is tremendously large, measuring more than 2 mm logn and 1-1.5 mm wide, while it measures approximately 350 mum in diameter. Therefore, distance of the nuclear migration in the egg cytoplasm is conspicuously long in the former and shot in the latter. According to comparison of cell size of egg cells and fusion manner of gametangial nuclei formation of the identical structure is expected in plants of the family Pineaceae.