| The salt-alkalization of soil has become the main ecological problem of grassland in Songnen Plain in the west of Jilin Province, which has become an inhibition for the livestock industry. Leymus chinensis is a kind of perennial grass with rhizomes, which is the dominant specie in plant community on local grassland, and has a strong tolerance to alkali-saline soil. The growth of A. chinense is relevant to health of grassland, and the growth is influenced by alkali-saline stress. Therefore, a research in the effects of alkali-saline stress on the growth of rhizome of A. chinense has a significant meaning, both in theories and practicality. It is advantageous to clarify the regulation and relation between soil salt-alkalization and the growth of rhizome of A. chinense theoretically, and also provide the theoretical basis for recovering the ecosystem of A. chinense grassland.By means of two years'successive research in the wild, in this paper, we discussed the regulations of rhizome diameter, branch angle, module density, section distance, root biomass, alkali spots invasion in different gradient of alkali-saline stress. In order to compare the change in above targets in alkali-saline stress, and study the mechanism of A chinense for responding to alkali-saline stress, which will provide foundation for recovering the ecosystem of grassland salt-alkalization. The results are showed as follows:(1) The density of old rhizomes was promoted under proper alkali-saline stress intensity (A2), as the stress intensity became higher and higher (A3-A5). the inhibition to the density of old rhizomes became much stronger accordingly. In 2009.A2>Al>A3>A4>A5; In 2010.A1>A2>A3>A4>A5.However. due to the low density, the new ones didn't show significant regulations.(2) The density of rhizome modules was promoted under proper alkali-saline stress intensity (A2). as the stress intensity became higher and higher (A3-A5). the inhibition to the density of modules became much stronger accordingly. In 2009,A2> A1>A3>A4>A5; in 2010,A1>A2> A3>A4>A5.Though the regulation for density of tillers was not obvious.we still thought it was consistent with regulation.(3) The effect of alkali-saline stress on branch angles was not obvious, and didn't have significant regulations. The rhizome diameter under the strongest stress (A5) was obviously smaller than others. The distribution of frequency of diameter didn't show significant difference among different gradients. In 2009, it concentrated in 0.9mm-1.5mm;In 2010,0.8mm-1.29mm.While the effect of alkali-saline stress on section distance and section density had a similar regulation to that on density of modules, that is to say, the section distance was promoted under proper stress intensity, however, under heavy stress, it was inhibited.(4) The sensitivity of aboveground modules to response to alkali-saline stress was different from that of underground modules. Heavy stress obviously affected the density of the underground modules than that of the aboveground. For density of old rhizomes, the maximum was 3.25 times as much as the minimum; for density of leaves,1.54 times in 2009. In 2010,2.41 times for rhizomes,1.07 times for leaves.(5) The effect of alkali-saline stress on root biomass was also similar to the above. The value of biomass was higher under proper stress intensity, while lower under heavy stress intensity. In 2009 A2>A1>A3>A4>A5, in 2010 Al>A2>A3 >A4>A5.(6) In the research for alkali spot invasion, there was no invasion under A1.Branch angles, diameter and tiller density approached the maximum under the gradient A1/3. A0. A1/2 respectively. However, the regulation of above targets were not similar under other gradients.The other values we studied didn't show significant regulations under different gradient of alkali-saline stress, except for the density of the leaves, which displayed an increase as the alkali-saline stress intensity became higher.
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