| Leymus chinensis is the dominant forage grass in Songnen plain of China. It has a very powerful ability of asexual reproduction, and it is a typical clonal plant. In the same time, it also has a certain extent saline-alkali endurance. On the genet,ramet population and individual physiology levels, the clonal growth plasticity of Leymus chinensis under saline-alkali stress condition was studied in this paper after field researching and disposal in laboratorial spot. In the same time, the effects of different diversion(gray-green type and yellow-green type) and fertilization,auxin(NAA,6-BT,GA )supply,cutting to the clonal plasticity of Leymus chinensis were also studied. After field sampling and researching, we found that both the spacer length and the branching angle of Leymus chinensis increased while the saline-alkali stress degree of the habitats' soil increased. That is: when the conditions of soil were better, the clonal architecture showed more "phalanx" habit, while when the conditions of soil were worse, the clonal architecture showed more "guerilla" habit. The changes of clonal plasticity of Leymus chinensis was the result of adapting environment with high stress: In Songnen plain, saline-alkali soil is the main restrictive factor to the growth of plants, and in the habitat with high degree of saline-alkali soil, the guerilla architecture can let the ramets of Leymus chinensi span and got away from the bad habitat, accordingly avoid the harm of high saline-alkali intensity to the growth. In the same time, the guerilla architecture also can let Leymus chinensi occupy more area and acquire more resource. With the increase of the saline-alkali degree of soil, the inter node length tended to descend. Making further analyse to the frequency distribution of inter node length, we found that the proportion of shot inter node was increased with the increase of the saline-alkali degree of soil. The plasticity of the inter node length of Leymus chinensi was also an effective mode of using resource. The population characteristics such as ramet density,ramet height and biomass et al. represented a low-high-low tendency, that is Leymus chinensis grew better in the habitat with the lighter degree of saline-alkali soil. In such habitat, the saline-alkali soil and the interlaced rhizome of Leymus chinensi can restrain the inbreak and growth of the other weeds. Besides the effect of saline-alkali stress, the effect of different concomitant plant to the clonal growth of Leymus chinensis was different. The accumulate of praline is protective response of adapting adversity. The proline content of Leymus chinensis increased while the saline-alkali degree of the habitats' soil increased. That is, when the intensity of saline-alkali stress was higher, the praline content in the Leymus chinensis was higher.With comparisons of the clonal growth of Leymus chinensis between different growth periods, we found that the clonal architecture of Leymus chinensis in after-fruit period showed more "phalanx" habit with the conditions of soil of the habitats becoming better. The ramet population characteristics of Leymus chinensis (especially the figure of adventitious buds) in after-fruit period were all higher than those in growth period. It showed that the sexual reproduction restrained the clonal growth and asexual reproduction of Leymus chinensis. With artificial controlling in laboratorial spot, influences of fertilization ,auxin(NAA,6-BT,GA) supply,different diversion and cutting on the clonal plasticity of Leymus chinensis were investigated. Under the same degree of saline-alkali stress, the clonal architectures of gray-green type showed more "guerilla" habit than which of yellow-green type, and the growth rate of gray-green type was also higher than that of yellow-green type. But the praline content of gray-green type was less than yellow-green type. The clonal plasticity to saline-alkali stress of gray-green type adapted the saline-alkali habitat better, and this was the causation t...
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