Eco-genetic Analysis On The Variation And Differentiation Of Leymus Chinensis Populations In Mid-Eastern Inner Mongolia Steppe

In the thesis, the variation and differentiation of Leymus chinensis in different scales (populations from different locations of Mid-Eastern Inner Mongolia steppe and different habitats within the Xilin River basin) were studied at population level, individual level and molecular level by using morphological, ecological, physiological and molecular biological approaches. The differentiation among the populations and genetic diversity within the populations were interpreted from the standpoint of population biology and molecular genetics, and the relationships of intraspecific variation and differentiation with environmental factors were also analyzed.There existed large differences in quantitative characters and distribution of L. chinensis in different communities. The species composition and dominant species of the communities showed zonal changes with decreased moisture from the east to the west in the region: the better the habitat quality, the more complicated the composition of the L. chinensis communities and the more evident dominance of L. chinensis. Meanwhile, the species composition and dominant species of the communities also showed azonal changes due to the influences of the local environment. Spatial variations were found in some quantitative characteristics among different L. chinensis populations-an important dominant species of the communities. Density and biomass of L. chinensis decreased and its dominance was replaced by tussock grasses with the change of environmental factors, especially the decrease of soil water content, which might be an adaptive response in natural conditions.Significant differences were found in leaf length, leaf width, leaf number per ramet and tiller number per plant among L. chinensis populations, which were not asynchronous, and the coefficient of variation (CV) varied from 4.69% to 30.46%. The CVs of leaf number (4.69%) and the ratio of leaf length/width (6.73%) were relatively small, while the number of asexual reproductive organs (tiller number per plant) and tiller size (dry weight per ramet) varied greatly, with CV 27.91% and 30.46%, respectively. Moreover, the variation and differentiation of L. chinensis were also observed in rhizome traits and biomass allocation pattern.Comparisons of six L. chinensis populations in chlorophyll content, chlorophyll fluorescence characters, photosynthesis and water metabolic characters were as follows: no significant differences existed in chlorophyll content and chlorophyll a/b ratio, and the initial fluorescence (F0), which reflected the chlorophyll content, showed similar results; while the chlorophyll fluorescence parameters, whichreflected chlorophyll function, photosynthesis and water metabolism, varied among the L. chinensis populations to some extent, which implied that there existed some variation in energy metabolic characteristics among them.Different L. chinensis populations showed different capacity of adaptation to osmotic and soil drought stresses. Compared with the other two populations-Yangcaoyangdi population and Gasong Mountain population, the Abaga population had less decrease in LWC and less increase in membrane permeability, maintained higher root activity, had increased root/shoot ratio and less decreased leaf length growth rate under osmotic stress. The Abaga population showed recovery growth in the later stage, while the other two populations decreased continually. The Yangcaoyangdi population and Gasong Mountain population were listed in various orders with different characters under osmotic stress. Responses of defense enzymatic system to osmotic stress varied among different geographic populations of L chinensis. There were significant differences in rhizome dry weight, root dry weight, underground dry weight, aboveground dry weight and root/shoot ratio among three L. chinensis populations under soil drought stress. The three populations tended to accumulate some osmoticly regulatory substances especially free proline. Contents of free proline, soluble sugar and soluble protein increased largely...