Preliminary Study On Seed Biology Of Orchid In Hainan

Orchidaceae is one of the largest families of angiosperms which has tremendous ornamental and economic value. Excessive collection by human and orchids' demanding habitats, additional its complex breeding system, many orchids nearly extinct, particularly the tropic orchids. All wild orchids in the world were catalogued in the'Convention on International Trade in Endangered Species of Wild Fauna and Flora'(CITES). As the traditional reproduction of orchid needs long period, and the reproductive rate is low. It can not satisfy market demand. However, orchid fruit have large number of seeds; study on their biological characteristics will be an important way to protect orchid germplasm resources.The seeds of wild orchid were investigated, including morphological analysis, activity assay and cryopreservation test, the conclusions are as belows:1. Seeds morphologyWe study 15 kinds of orchid seeds morphology in Hainan, including 4 terrestrial and 11 epiphytic types.The seed or embryo size, testa color, and seed shape were vary among genera and species. These data can be used as the parameter for the taxonomy of Orchidaceae.2. Orchid seed viability testEstablish one method for orchid seed viability test taken Doritis pulcherrima as material. Pretreatment by 2ml of 5%(w/v) Ca(C10)2 solution (containing 0.8% Tween 80) 30 min, then soaked by distilled water 24 h, at last 1%TTC(w/v) treated 24 h in dark under 30℃condition. Staining rate is similar to germination rate. This method is suitable for orchid seed viability test.3. Cryopreservation of orchid seedIn this paper, we cryopreserve the seeds of Dendrobium chrysant Hum and Doritis pulcherrima L by rapid cooling or vitrification with PVS2 (plant vitrification solution 2) pretreatment. The optimal period is 45 min and 60 min respectively. There is no ultra-low temperature tolerance for 30 d of the Doritis pulcherrima L seeds, and 30% survival rate for 45 d seeds. The survival rate increase with the age of embryo. Vitrification is better than rapid cooling.4. Establishment breeding system of Doritis pulcherrima L.Doritis pulcherrima L is raceme. This study used four way of pollination: self-pollination, different flowers selfing-pollination of the same inflorescence, geitonogamy and cross-pollination. Doritis pulcherrima L is mixed mating system; all the pollination methods show a certain affinity. Cross-pollination is the best pollination method with more than 90% fruit set and highest embryo rate. The germination capacity is high after 90 d pollination. Germination rate increases with embryo age.