Conservation Biology And Landscape Application Of Trigonobalanus Doichangensis (A.Camus) Forman, A Rare And Endangered Plant In China

For probing into the endangering mechanism and planning the conservation strategies of Trigonobalanus doichangensis, the 2nd priority species of the national key protected plants of China, the ecology, reproductive biology/ecology, genetic diversity and cytology of the species have been detailed studied for the first time in this dissertation. Meanwhile, the habits, ornamental characters, propagation and cultivation, and application in landscape architecture of T. doichangensis for Ex-Situ conservation, have also been disserted.1. Investigations revealed that T. doichangensis is still existing in its natural habitats in Yunnan of China and north Thailand. However, the habitats are extremely fragmented and the populations are isolated each other. The vegetation destruction caused by the agricultural land expansion and cuttings of the species for fuel-wood are forming its endangering habitats. The alien species Ageratina adenophora, Chromolaena odorata and Tithonia diversifolia have already invaded into communities in shrubbery layer, and they are inhibiting the species regeneration.2. Based on the field observation and data analyses, the threat category of T. doichangensis in China is proposed as EN[B1a,B1b(i,ii,iii)] according to IUCN Red List Categories and Criteria:Version 3.1.3. Although T. doichangensis did not show any abnormal phenomena in anther wall development, microspore genesis and male gamete of formation. However, both percentages of the well developed nuts (containing embryos) and nut (commonly called seed) germination was less than 10%. And also only 40% of the fresh pollen was fertile and the germination needed 8h after culturing under darkness. Certainly, the species exists the reproductive barrier4. Karyotypes of all the 4 T. doichangensis populations were 2n=14 = 10m+2sm+2st+2bs. Compared with chromosome numbers of T. verticilata it can be confirmed that the base chromosome number of genus Trigonobalanus is x =7. And also some B chromosomes at the prophase were observed. Although the karyotype variation both within and among the populations of the species was limited, but the discovery of B chromosomes may imply that the lower fertility of T. doichangensis would be partly attributed to the formation and accumulation of the B chromosomes.