Reproductive Biology Of Cypripedium Japonicum

C. japonicum Thunb, a perennial herb of orchidaceae, with unique flower shape, brilliantflower color, unique ornamental value and medicinal value. Due to over-harvesting and theenvironment changes,a large number of wild populations of C. japonicum reducing, somegenetic resources has been lost, in endangered, has been listed as national endangered plants.Consequently, it is essential to excute studies on Reproductive biology of C. japonicum fordiscussing its extinct mechanism.We conducted a field of investigation, out crossing index, emasculation, bagging andartificial pollination, studied the flowering character, pollen viability, stigma receptivity,breeding System of C. japonicum in natural populations. And we also observed surface ofpollen and stigma using electron microscope. The capsules of C. japonicum in differentdevelopment stages were collected and the growth dynamic of the fruits was studied. Seedviability was examined within TTC (2,3,5-triphenyl tetrazolium chloride) test solution andmicroexamination was made to observe embryo development by paraffin embedding andscanning electron microscope at each collection stage. The results were as follows：1. Breeding strategy of C. japonicumC. japonicum has two reproductive modes： generative propagation and vegetativepropagation. The generative propagation needs effectual pollinating agent and form the seedsby fertilization which grow up to tree seedling eventually. The multiply of C. japonicummainly adopts vegetative propagation which form buds on the rhizome. From June to July ofthe first year, the buds emerge on the rhizome. With the development of buds,they outcrop inOctober to November and lay dormant in winter. In the next year, they start to grow in Marchto April.2. The blossom biology of C. japonicumThe population comes into bloom from April to June and the flowering span amongpopulations is23days. The life span of one single flower was approximately12-16days. The stigma receptivity would be existed until the flower season was over and pollen viability washigh in the whole florescence. The stigma exceeded stamen in position and the relative positionbetween the stamen and style was always unchanged in the whole flowering process.The total value of OCI is4. Seed set propagation coefficient of C. japonicum is low underfield conditions which turned out to be only5%. Based on the results of emasculation, baggingand artificial pollination studies, C. japonicum is self-compatible and can't self-pollinateautokineticly nor has a syngamy. The breeding system is pollinators depended.3. The growth of embryo of C. japonicumThe elapsed time between pollination and maturation of the ovule in C. japonicum isabout35days. The ovules are weakly developed before pollination, cell proliferation isinitiated along the placental ridges of ovary. The placental ridges continue to prolong andbranch to form finger like ovule primordia by about10days after pollination. The innerintegument appears near the tip of primordia, and the outer integument is initiated later. Thearchesporial cell developes to form the megasporocyte and gives rise to the mature embryo saceventually.The embryogeny conforms to the caryophyllad type. The first zygote division wasunequal, producing a basal cell and a terminal cell. Terminal cell gave rise to the embryoproper and it did not participate in the formation of suspensor. The derivatives of the basal cellgave rise to the suspensor. Suspensor consisted of a single cell that was highly vacuolated. Nofurther divisions or enlargement of the suspensor could be seen through the early globular stage.The single-celled suspensor degenerated at the advanced stage of the embryo development.After fertilization, the inner tegument of this spcies remains during the whole process of seeddevelopment and a layer of impermeable endothelium is formed.Mature seed consists of endopleura, episperm and globular embryo. Air cavity existsbetween the endopleura and episperm. Viability of seeds was high, the percentage of viableseeds was56%, so it is not responsible for the low germination percentage. Tight seed coat, theabsence of micropyle in mature seed and smaller embryo proper may be related to the lowgermination. 4. Fruit growth dynamics of C. japonicumThere are three carpels in the ovary of C. japonicum and are divided into six valves: threeare fertile and three are sterile. The increase in the fruit diameter results mainly from theincreased volume of mesocarp cells and not from the number of cell layers. The fruit growthcurve was gentle, and the entire development period may be divided into4stages: first fastgrowth period, first slow growth period, second fast growth period and second slow growthperiod before morphological maturity.