The Correlations Analysis Between Endogenous Hormones And Growth,Population Building Of Leymus Chinensis In The Songnen Salinity-alkalinity Grassland

Leymus chinensis is a perennial rhizomatous grass and has high tolerance to adverse environmental stress, which can distribute in a variety of soil types. L. chinensis is one of the main constructive species in Songnen grassland, and which is an excellent pasture with high stress resistance and productivity. The physiological and biochemical processes of L. chinensis have changed significantly because of growing in the adverse environments for a long time. It is important to illuminate the relationship between plant endogenous hormones and plant photosynthesis, population construct and productivity, which can help us to understand the mechanism that salt affect the growth of L. chinensis and provide new theoretical basis for saline grassland revegetation and grassland resources sustainable development.This experiment was conducted in Songnen Grassland Ecological Station of Northeast Normal University in Jilin Province. We selected L. chinensis as experimental material. Five sample plots were set up according to soli salt and plant density, and keep 100 cm distance between each sample plot.Soil physiological parameters(concentrations of K+ and Na+, pH, electricity conductivity), plant leaf photosynthetic parameters(photosynthetic pigment content, gas exchange parameters, soluble sugar and soluble protein content, etc.), hormone content(Auxin, IAA; Gibberellin, GA3; Abscisic acid, ABA), antioxidant enzyme activity(POD, SOD, CAT, organic acid and proline), population characteristics(plant density, height, biomass) were determined in different saline degrees in Songnen grassland. The aim of this research to understand the effects and mechanism that plant endogenous hormones affect L. chinensis population construct by discussing the relationship between plant endogenous hormones and the population characteristics and light contract capabilities of L. chinensis.The result showed that the plants promote growth hormones IAA and GA3 decreased and ABA increased with the increase of soil salt, the concentrations of these three hormones increased with the delay of time and which reached the maximum at growing season in July.Soil salt decreased the synthesis of IAA and GA3, but stimulated the synthesis of ABA in leaf of L. chinensis. Under salt stress condition, GA3 and ABA significantly increased L. chinensis net photosynthetic rate, and IAA suppressed the content of chlorophyll. In a word, endogenous hormones of L. chinensis regulated the chlorophyll content, etc, and decreased photosynthetic capacity and photosynthetic products under salt stress.After analyzing the correlation between the content of IAA, GA3, ABA and content of antioxidant enzyme, cations, we found that L. chinensis changed Change the content and activity of certain substances in vivo when salt stress present, which can alleviate the destroy caused by salt via increasing the activity of antioxidant enzymes, proline concentration, reducing the toxicity of Na+ and changing content of organic acid.In addition, the changes of IAA and GA3 in leaf of L. chinensis significantly affected population density, height, aboveground biomass. The population density and height of L. chinensis decreased with the increase of soil salt concentrations, thereby caused grassland degradation.Our results suggested that plant hormones play a vital role in plant population built up, plant development and metabolism in Songnen meadow ecosystem. The result highlighted that salinization of grassland restoration, L. chinensis breeding and cultivation, construction of artificial grassland.