Comparative Studies On Reproductive Characteristics Of 13 Dioscroea Species And Primary Trials On Tissue Culture Of The Species

Genus Dioscorea (Dioscoreacea) is a kind of perennial twisted herbal lianas.A number of species in the genus are used as herbs. The study consists of three parts. 1) Morphology and structure of floral organs of 13 Dioscorea species. The evolutionary relationships of 13 species were discussed according to observed morphological and structural characteristics. 2) Differentiation of floral buds, biogenesis and development of microspores and male gametes, as well as embryogenesis. 3) Non-sexual propagation.The followings are the major results.According to observation, most species have cymes or racemes in male individuals. This character may expose more pollens to the females, thus is benefit for reproduction of progenies. Structural research on floral organs of the 13 species shows the varied characters between different species.Anatomy and development of male flower in Dioscorea collettii Hook f.var.hypoglauca were systematically investigated with paraffin embedded sectioning and morphological observation in field. The results showed that the some floral organs seem degenerated developmentally, for example, the staminate connective were forky and thicken, however, the staminodia presented filamentous with a forky or strumose apex. The evolutionary trend of flowers was discussed in this paper.Microsporogensis and the formation of male gametophyte in D.collettii Hook.f.var.hypoglauca (Palibin) Pei et Ting also were studied. The conclusions include: the anther is tetrasporangiate and the development of the pollon sac wall belongs to monocotyledonous type, endothecium does not develop to fibular thickenings. And the tapetum is of the glandular type with two cell nuclei. The cytokinesis of the microspore mother cell in meiosis belongs to simultaneous type. Most of the microspore tetrads are tetrahedral and there are still a few other types, such as isobilateral shape. Mature pollen grain is of the 2-celled type.According to the observations of the megasporogenesis and the formation of female gametophyte in D.collettii Hook.f.var.hypoglauca (Palibin) Pei et Ting, the ovule is bitegminous; the development of the embryo sac conforms to Polygonum type.Tissue culture of D.opposita Thunb.and D.bulbifera througeh was explored with bulbil and young stem above the ground. The results indicate that MS+6-BA2.0mg/L+NAA2.0mg/Lmedicum is perfect for the callus formation of D.opposita Thunb.and D.bulbifera, and the non-sexual clone lineage was established with the plate culture.