The Physiological And Morphological Responses Of Leymus Chinensis To Saline–alkali Stress

In this study, we choose Leymus chinensis as the study object, to investigate the response mechanism of L. chinensis to salt-alkaline stress at population ecology and physiological-ecology levels. We systematically studied the growth law of rhizome, and the growth outward and habitat-colonizing-strategy of L. chinensis under salt-alkaline stress through field observation and artificial simulation of L. chinensis in Western Jilin Province. The changes of endogenous physical characteristics, morphological characteristics, and the density of clonal components under the stress were analyzed. The main results were summarized as follows:1. The morphology response of L. chinensis rhizome under saline-alkali stress.The module changes of L. chinensis underground part in different saline-alkali gradients were consistently varied during the growing season. Rhizome density and branching angle were negatively correlated with saline-alkali stress. The rhizome internodes and spacers increased with the increase of stress. With increasing saline-alkali stress, specific root length, per unit length of rhizome biomass, root-shoot ratio, increased to varied extent, showing that L. chinensis rhizomes is adapted to high saline-alkali concentrations in the soil environment with a self-regulating, enhanced survivability, and strong saline-alkali tolerance.2. The ecological and physiological response of L. Chinensis rhizome under saline-alkali stress.Rhizome biomass, rhizome density, branching angle, root density, and root biomass were minimum under the strongly saline-alkali stress. Rhizome internode length and specific root length gradually increased with the increase of stress. Root-shoot ratio and per unit length of rhizome biomass under different saline-alkali stress were not significant among groups. The content of Na~+, K~+, K~+/ Na~+, malondialdehyde(MDA), proline and organic acids(OAs) were significant differences under different levels of saline-alkali stress, and the presence of different organic acids. The activity of antioxidant enzymes increased with the increase of saline-alkali stress. With the increase of saline-alkali stress, the allocation of rhizome biomass increased, branching angle decreased, which were beneficial to the rhizome escaped from the original saline-alkali habitat.3. The colonization of L. chinensis in different saline-alkali bare patches.There was a significantly reduction in the plastic module of rhizome density, node density, leaf density and tiller density with the increase of saline–alkaline stress. But bud density increased with the increase of saline–alkaline stress. Morphological plasticity changed rhizome diameter and branch angle increased significantly, but rhizome internode length and spacer were reduced markedly; leaf and rhizome biomasses were significantly reduced, but root-shoot ratio was maximum in the heavy saline-alkali soil. There was a linear increase in the content of Na~+, K~+; the content of chlorophyll was decreased, while proline, MDA, organic acids(OAs), activity of antioxidant enzymes, and soluble protein along with soluble sugar were increased with the increase of saline–alkaline stress. Under the saline–alkaline stress, K~+, OAs, soluble protein and total soluble sugar gathered in the leaf, were higher than those in the rhizome, however, the proline, MDA, and protective enzyme gathered in the leaf were lower than those observed in the rhizome.4. The diffusion mehanism of L. chinensis under different levels of saline–alkali stress. ~+In saline-alkali habitat, there was an increase in the content of Na~+, betaine, OAs, and soluble protein in leaf were higher than those in rhizome, There was a contrary tendency of the content of proline, MDA, protective enzyme and soluble sugar, all of which were increased with the increase of saline–alkali stress. The module density showed a wavy variation along with the increase of saline–alkali stress. Under the saline–alkali stress, rhizome biomass, leaf biomass and root–shoot ratio decreased followed by an increase. While the change of the root biomass showed a contrary tendency, and the specific root length increased gradually. There was a significant correlation among root–shoot ratio, specific root length, and the physiological modules.