【作者】 马宇飞；

【导师】 李俊清；

【作者基本信息】 北京林业大学 ， 生态学， 2004， 硕士

【摘要】 珙桐是我国特有的珍稀濒危植物，探讨珙桐的濒危原因可以更加有效的保护这一物种。而从种群生态学和胚胎学两方面是从宏观和微观的角度探讨濒危原因。 通过对七姊妹山珙桐种群结构的调查，发现珙桐的径级结构呈倒金字塔型，都以大树的数量为多而缺乏幼苗。根据静态生命表，得出珙桐种群幼树死亡率高，后期生长稳定。种群存活曲线趋向于Deevey-Ⅱ和Deevey-Ⅲ之间，高径级种群趋向于稳定，低径级种群反之，幼年个体补充不足。珙桐的更新，种子资源从数量上看并不缺乏，但真正有生活力的种子的数量并不多。无性繁殖是珙桐维持种群延续的重要手段。 通过对珙桐在湖北五峰后河的空间分布格局的研究，珙桐的种群偏离随机分布显著，由x~2检验和测定的各集聚强度指数也一致反映出琪桐种群的分布格局服从负二项分布，属集聚分布类型，水分和土壤因子是影响其生长进而影响其分布格局的主导因子，这种分布虽然增强了种群抵御不良环境的能力，但不利于琪桐扩散，对珙桐濒危有一定的影响。 大多数的濒危植物都存在有性生殖障碍，通过对珙桐的大小孢子及雌雄配子体形成的研究，发现在这一过程没有异常。其中，小孢子母细胞减数分裂为同时型，成熟花粉为2胞花粉，胚珠为厚珠心，成熟胚囊具八核。 通过对珙桐濒危机制的探讨，有针对性的提出了珙桐保护的建议，认为就地保护和适度认为干扰是关键，同时要突破繁育难关，进行一定的迁地保护，并加大宣传力度，使人们认识到保护珙桐的重要性。更多还原

【Abstract】 Davidia involucrate Baill is one of the rare and endangered plants in China. To discuss the endangering mechanism of Davidia involucrate Baill is helpful to protect it. The paper studies the reason of endangering mechanism of Davidia involucrate from population ecology and embryology.Through the investigation on population structure of Davidia involucrate in Mt.Qizimei Nature Reserve of Hubei Province, it’s discovered that the size structure belongs to the shape of the reverse pyramid, and according to the life table ,it’s concluded that the death rate of young tree is high and the survival curve has the trend to be the type between Deevey II and III,the population was stable in large size class and variable in small size class. The population was lack of seedling and the regeneration of Davidia involucrate was the combination of sexual reproduction and asexual reproduction.The spatial distribution pattern of Davidia involucrate was studied in Houhe Nature Reserve, Hubei province, and the result shows that the population of Davidia involucrate has a pattern of clump. Damp and soil were the major factors determining the distribution pattern of Davidia involucrate population. In one hand, this kind of distribution enhanced the ability to withstand the adverse environment condition, in another hand, this kind of distribution had no benefit to extend the population and had some effect on the endangered state of Davidia involucrate.Most of the endangered plant has the difficulty in sexual reproduction. Through the study on the megasporogenesis, microsporogenesis and development of gametophytes in Davidia involucrate, we found that there is no abnormal phenomenon in the process. The meiosis of microspore mother cell belongs to simultaneous type and the mature pollen is two -celled, and ovule is crassinucellate. Mature egg apparatus has eight nucleuses.In the end, some suggestion on the protection of Davidia involucrate was proposed and in-situ conservation and proper disturbance is considered to be important, at the same time, ex-situ protection and the study on reproduction must be carried out and propagandizing the importance to protect Davidia involucrate is necessary.更多还原