作 者 ：Chen Zu-keng, Li Ying and Wang Fu-xiong Wang Fu-hsiung
Keywords:Spermatogenous cell, Sperm, Egg, Fertilization, Cephalotaxus fortunei, C.oliveri,
Abstract:The structure of spermatogenous cell of Cephalotaxus is unique among the gymnosperms. While towards the mature stage, its nucleus is close to one side of the spermatogenous cell, and on the other side there is abundant and prominent . cytoplasm, which contain a group of the aggregate cytoplasms of radial arrangement similar to blepharoplast of spermatogenous cell of Ginkgo. But, there are two opposite blepharoplasts at either side of the nucleus in Ginkgo, and while there is only one blephareplast at one side in Cephalotaxus. This is one feature of the sexual process in Cephalotaxus. When the pollen tubes approach the top of the archegonia, the division of the spermatogenous cell takes place and there are two almost similar sperm cells both in size and morphology. It is interesting to note that the cytoplasm of the sperm cell contains certain granules of nucleolus-like structure, which appears to be a rare phenomenon among the gymnosperms. This is another feature of the sexual process in Cephalotaxus. These two features are the important characters of Cephalotaxaceae. The egg morphology of Cephalotaxus is also unique among the conifers, its outline looks like a carrot. The upper part of the egg is rather wide and is about 85 to 108 μm in width. On the other hand, the opposite end is gradually becoming narrow and about 910 to 1100 μm in total length. So the ratio of the length and width in the egg of Cephalotaxus is about 10:1. The structure of the egg in Celhalotaxus fortunei and C. oliveri have the following common feature: 1. When their eggs mature the cytoplasm of the egg at lower part of the nucleus possesses deep- staining and fine granules of 2 to 3 groups of aggregate cytoplasm. 2. During maturation of the egg, some of the granules of nucleolus-like structure are scattered in the cytoplasm. As fer- tilization takes place the number of these granules reaches the peak. This condition has been encountered in the egg of Amentotaxus argotaenia. Therefore we could conclude that they are closely related between Cephloraxaceae and Taxaceae. The fertilization of Cephalotaxus fortunei occured on May 10 to 24 (1983), and that of C. oliveri took place on May 28 to June 13 (1983). The fertilization of the genus belong to the type of undergoing mitosis prior to complete fuse of both male and female nuclei. This type of fertilization has been found only in Pinaceae and Cephalotaxaceae. After fertilization the structure of fertilized egg becomes prominent in polar organization. In other words, the cytop- lasm at upper part of the fertilized egg becomes highly vacuolated and that at lower portion, conversely, is rich in abundant proteinous vacuoles and certain granules of nucleolus-like structure dispersed in the cytoplasm. Because the division and differentiation of the proembryo are proceeding at the base of the archegonium, the large inclusions and the nucleolus-like granules may be involved in the nourishing and development of the proembryo.
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