Studies on Microsporogenesis and Development of Male Gametophytes in Endangered Species Glyptostrobus pensilis

Glyptostrobus pensilis is an endemic and First Grade critically endangered species in China.To research the reproductive biology of G.pensilis in relation to its influence on the endangered status,microsporogenesis and development of male gametophytes were observed using paraffin wax sections.The results were as follows:The male cone differentiated in mid-October,and the microsporangium wall, which was composed of the epidermis,a middle layer and a tapetum,occurred in early November.The microspore mother cells formed at the beginning of December,and meiosis of the microsporocyte occurred in mid-December.The tetrads were formed as isobilateral and tetrahedron forms in mid-January of the following year,and the microspore tetrads eventually separated and the microspores were released in late January.Pollen matured in mid-February and were shed in the form of two cells over two weeks.After pollen shedding,the pollen tube was produced in March,and the spermatogonia,tube nuclei and sterile nuclei occurred in late March.The pollen tube contacted the top of archegonium,and the spermatogonium then divided into two sperm waiting for insemination in late May.Deformation and abortion were observed in the process of microsporogenesis and the development of male gametophytes,whose percentage was low.There was no influence on normal pollen shedding.Microsporogenesis and development of male gametophytes,which were normal,were not the main factor influencing the endangerment of G.pensilis.