Studies On Gametophyte Development And Oogenesis In The Fern Stenoloma Chusanum And Hicriopteris Glauca

Gametophyte development and the studies on oogenesis are important aspects in sexual reproduction of the fern. Archegonium is the reproductive organ which can produce the egg cell. The archegonia formed firstly in the bryophytes and degenerated in the ferns,the gymnosperms, and disappear in the angiosperms, which indicated that the archegonia and their oogenesis are related with the phylogeny of the plants. And ferns are a transitional group, which lie between the lower plants and higher plant taxa.Their gametophytes and sporophytes are independent survival, which are unique in the higher plants. Thus, the ferns are excellent materials to study the gametophyte development and gametogenesis of the higher plant. The series of studies in our laboratory demonstrated that the core leptosporangiopsida had obvious egg envelope and fertilization pore. But Osmunda japonica which is the base group of leptosporangiopsida has no egg envelope and fertilization pore structure. Therefore,the evolution of egg envelope and fertilization pore in ferns of different evolutionary status are unknown. Stenoloma chusanum which has special evolutionary status is between core leptosporangiopsida and Polypods, Hicriopteris glauca which has special evolutionary status is between O. japonica and core leptosporangiopsida. So,the studies of oogenesis in S. Chusanum and H. glaucamay have important scientific significance in revealing the formation of the egg envelope and fertilization pore. The present studies have the significance in clarify the cytology mechanism of oogenesis and reveal the evolution of sexual reproduction in fern.The major contents and results of this study are as follows:1. The development of gametophyte of S. Chusanum and H. glaucamay undergoes the stages of the spore germination, filament, plate and prothallus.antheridia and archegonia of S. Chusanum and H. glaucamay are produced under theapical notch of the prothallum; S. Chusanum in the gametophyte development have no hair porduced, but on the mature prothallus of H. Glaucamay produce hair on the edge of its mature prothallus.2. The oogenesis process of S. Chusanum and H. glaucamay undergoes stages of initial cell, primary cell, central cell and egg cell development, among which the egg development is the key stage in oogenesis. These studies showed that the two species share some similar charateristics other core leptosporangiopsida.3. The ultrastructural observations showed that the development characteristics of oogenesis in S. Chusanum and H. Glaucamay are similar with the advanced ferns.They all have pore region, fertilization pore and extra egg membrane. But the egg membrane in S. Chusanum is simpler than in H. Glaucamay. The egg membrane of S.Chusanum’s has only one layer of vesicle containing the osmiophilic materials, but H.Glaucamay’s egg membrane has three or four layers.4. In the process of egg’s development in S. Chusanum, the nucleus is no nuclear evaginations formed. But the nucleus produces numerous nuclear evaginations in the develoment of the egg in H. Glauca, and the numerous nuclear evaginations will be continuously move out of the nucleus and into the cytoplasm.5. During oogenisis of S. Chusanum, there are more plastids in the egg cytoplasm, its starch grains is abundant. During oogenisis of H. Glaucamay, there are less plastids in the cytoplasm, the starch grains is not obvious, but the lamella structure is obvious.Our study fristly clarify the particular process of the development of archegonium and oogenesis in S. Chusanum and H. Glaucamay. It reveals that S.Chusanum is between core leptosporangiopsida and Polypods, and H. Glaucamay belongs to the development ferns. It can provides abundant data to reveal the mechanism of the fertilization and sexual reproduction of S. Chusanum and H.Glaucamay. And it can also lay a foundation for evolution of sexual reproduction of ferns.