The Ecological Adaptation Mechanism Of Saussurea Stella Maxim.

Saussurea stella is mainly distributed in alpine pasture and meadow of Qinghai -Tibet Plateau. It's likely that alpine environments and herbivores have played an important role in their ecological adaptation mechanism. This study mainly includes undermentioned subjects:Integrated research of growth habit and life history shows the biennial, specific rosette shape attribute to adaptation to the harsh alpine conditions, but also response to the grazing of herbivores. It's dwarfish shape and underground meristem avoid most nutritive organs being eaten and trampled, moreover are profitable to the seedling's overwintering and resistance of ultraviolet radiation.The statistical analyses of individual feature, population dynamic and seed germinating capacity shows S. stella has close relationship with herbivores. The selective pressure imposed by herbivores is a crucial factor for its special biological traits. It also can be seen that the grazing of herbivores can significantly increase the fitness of S.stella by virtue of undermining the interspecific competition. That means grazings of herbivores are beneficial to the survival and expanding of population of S.stella in alpine pasture ecological system.The pollination biology, physiological characteristic and ecological significance of red leaves were extensively investigated. The results indicate that the conspicuous red coloration of leaves during propagative phase is possibly not due to abiotic stress factors and have not find any significant physiological function. The red wild type and green mutant have no difference in the pollination preference and seed germinating capacity which indicate red coloration is not attractive to pollinators (bumblebees).The dominating flavonoid component derived from alpine strong ultraviolet radiation, in addition flavonoid is also important compound which can protect the inflorescence not to be grazed. Flavonoid make S.stella is unpalatable and the dominant herbivorous cattle and yaks behaved obvious rejective reaction to S.stella individuals holding on man's hand. The signal of low palatability is transmitted to herbivores by conspicuous red leaves. Red coloration is profitable for herbivores to...