Preliminary Study on the Megagametophyte and Embryological Development of Isoetes sinensis

Isoetes sinensis Palmer belongs to Isoetaceae,it's an herbaceous fern-ally and an old endemic species from middle and downside of the Yangtze River. It is extremely sensitive to environmental pollution,and falls under national level protection of extreme endangered wild plants. The gametophytes of Isoetes sinensis were cultivated artificially. We observed the development process of megagametophytes and embryos based on different developmental stages,using paraffin section. Results show that the megaspore germinated when fostered for 15-20 days. The megagametophytes were spherical and belonged to intramural development type. Between 8 to 20 archegonia formed in each megagametophyte. The development of mature archegonia had many possibilities. Only neck canal cells and ventral canal cells degenerated,and eggs had the chance to fertilize. The zygote first proceeded to transverse division,and then developed into dozens of spherical embryo cells when fostered for about 50 days. After 80 days the megagametophyte cells become atrophied,the structure of the first leaf,ligule and first root were more obvious,and the second leaf also appeared. This paper discusses preliminary research on the reproductive biology mechanism of endangered Isoetes sinensis Palmer.