Comparative Study On The Reproductive Development Of Isoetes Yunguiensis And I.Taiwanensis

Isoetes is the relict genus of Isoetacea. There are about 200 species around the word. They're the small herbal quasi ferns in the independent evolution of the classification system. It's has high research value in systematic. Isoetaceae is the group of worldwide distribution. But its origin and evolution route are still explored continually. At present, the proportion and quantity of Isoetes in China are in the condition of quickly reduce. Because of the destroy of environment and heredity.Many scholar who work on the Isoetes devoted themselves to explore the case of endangered. For further study the life history base on the anatomy, it's particularly important to the process and the way of reproduction. As a breakthrough point in this paper, we selected Isoetes yunguiensis and I.taiwanensis. To use hydroponic and soil cultivation methods on the gametophyte and sporophore. And for the observation of nutritive organ and the process of reproduction in especial to utilize TEM and SEM. The main results are as follows:The megagametophyte of I.yunguiensis and I.taiwanensis are intramural development type. Archegoniums are born in the megagametophyte. The composition and density in neck canal cell and ventral canal cell are similarity. No difference except for diameter size. The megagametophyte is divided into function area and nutrition area. The function area could develop into archegoniums. The main role of nutrition area is to provide nutrients for megagametophyte and archegoniums development. The nutrition area cells are made a difference morphology in the different development period of megagametophyte. The material inside or outside of microgametophyte and sperm cells are different. There are reticular, powder and filaments matter in I.yunguiensis. But there is only reticular matter in I.taiwanensis. These matter are related to the sperm cells development and the process of sperm into archegonium.Embryo development is similar in I.yunguiensis and I.taiwanensis. There are big nucleus in the edge of first root primordium cells and nucleolus is obvious. The cortical cells of the first leaf primordium are neat and have plastid. There are space between embryonic stem cells. And the content of cytoplasm is less. Sporangium asexual reproduction produces spores. Sorus changes during the development determines the future type of sporangium. Cells are similar in the early stage of sporangium development. The differentiation of fertile and infertility cells appear in the middle of development. Ligule have secretion function. Ligule is born in the base venter of sporophyll. The ligule cells in the embryo contain a lot of endoplasmic reticulum and golgi apparatus and other organelles. The nucleus is big and activity strongly.Sporophore of I.yunguiensis and I.taiwanensis are composed of three part. The first was highly shortening corm with secondary development which had protostele. And the xylem which had tracheid was surrounded by the phloem. The second was sporophyll growth from the top of corm. Mature sporophyll had diaphragm and four lacuna. The third was rhizoid growth from the bottom of corm.These two species of Isoetes were similar both in morphology anatomy and reproduction development but sill had distinguish characteristic. To comparative analyze and discuss the difference. Preliminarily revealed the reproductive mechanism and endangered factors of Isoetes from the perspective of genetics and ecology. Expect to explore further the genetic relationship of Isoetes. To accumulate the value resources about origin and evolution route and provide the feasibility technical support for the breeding and protection of plant.