Studies On Conservation Biology Of Sinowilsonia Henryi Hemsi.(Sinowilsonia), An Endangered Herb Endemic To China

Sinowilsonia henryi Hemsi., a deciduous tree of the genus Sinowilsonia belonging toHamamelidaceae family, lives in Shaanxi, Shanxi, Henan, Gansu, Hubei and Chongqingprovinces. The species have great scientific, economic and ecologic value, however itswild popuLation is hard to be found. To date, the species is regarded as endangered plantby both central and local government. To reveal the endangered mechanism ofSinowilsonia henryi Hemsi and provide basic research data for its protection, the researchon the biology, genetic diversity of biology and endangered mechanism of Sinowilsoniahenryi Hemsi was done from the view of embryology and popuLation geneticanalysis.wew studied, the resuLts were as follows:1.The feature of anther developmentThe early development of the stamens,the stamen primordia were formed, in its fourcorners, under a layer of epidermal cells division were active and formed archesporial cells.The periclinal division of the archesporial cell had formed the primary parietal cells andprimary sporogenous cells, after2times of split,primary parietal cells form to anther wallcells. Anther had two chambers, when anther wall fully differentiated, the wall wereorderly composed of three layers inside out：the epidermis,the endothelium and thetapetum.2. MicrosporogenesisEach anther had a layer of male archesporial cells, occured in beneath the epidermisof young anthers. The archesporium was divided into primary source cell and primarysporogenous cells by thepericlinal division. The microspore mother cells gave rise toisobilateral tetrads by meiosis, then quickly separated, free from anther wall, becomingmononuclear pollen. As cell graw, vacuoles appeared in the cytoplasm of cells, andgradually merge into a large central vacuole, cytoplasm and nucleus moved to the side.Mature pollen was spherical in shape, and has three apertures.3. Megasporogenesis and female gametophyteIn young ovary, tire seat differentiateed two ovule primordia. The archesporium wasdivided into a parietal cell and a sporogenous cell by periclinal division. The outer parietalcells followed goes several periclinal division and anticlinal division for increasing thenumber bead heart cell layers of the top of the bead. Sporogenous cells then developed intothe embryo sac mother cells, the embryo sac mother cells followed formed a linear tetrad by meiosis, only one cell far away from beads hole continued to develop into the embryosac. Mononuclear embryo sac formed two nuclear after first division, with the formation ofvacuoles, two nuclear sac moved to both ends and formed a two-nucleate embryo sac. Thedevelopment of Sinowilsonia ovule belonged to Polygonum-shaped sac.4.Analysis of Genetic DiversityThrough extracting DAN of Sinowilsonia, rDNA-ITS region was amplified by PCRand sequenced. Genetic analysis was conducted by using Clustal, DnaSP, MEGA, andAlequine software. The results showed that ITS had a total length of817bp, and no gap.The whole ITS had15variable sites,11converting sites,4transversion sites, and thenumber of information sites reached11. The genetic differentiation coefficient of AMOVAanalysis is0.5063, indicating that genetic variation of Sinowilsonia mainly existed amongpopulations, and the genetic diversity at the species level and group level were at lowlevels, the genetic differentiation among populations was significantly difference. Theresults of Mantel test (r=0.51, p=0.01) showed that the genetic distance betweenpopulations correlated with geographical distance, indicating the geographic isolationplayed an important role in the formation of genetic structure of Sinowilsonia population.5.Mechanisms of endanger and endangered species protectionThe endangered reasons of Sinowilsonia came from two aspects of its internal andexternal aspects. Internal factors mainly reflected in two aspects: First, Sinowilsonia hadlower adaptation of environmental changes for its ecological amplitude; Second, it was theslow-growing species, had small group populations, and easily generated genetic drift.External factors mainly reflected in the destruction of their habitats, declining the effectivepopulation of Sinowilsonia, leading to the increase of inbreeding and inbreedingdepression, and ultimately declined its adaptation and viability. Sinowilsonia geneticstructure of populations had been effected by the long-term historical evolution andecology, included changing distribution, habitat fragmentation and population isolation.Therefore, under the small populations and both large populations, this study formulated aconservation-based protection strategy in order to prevent the decline of their geneticdiversity.