Effects Of Arbuscular Mycorrhizal Fungi On Salt Tolerance Of Leymus Chinensis Of Songnen Grassland

Soil salinization is one of the important limiting factors of vegetation productivity in Songnen grassland.Leymus chinensis,a dominant species of azonal vegetation in salinized grassland of the Songnen Plain,showed strong ecological adaptability to saline-alkali stress.Arbuscular mycorrhizal fungi can form a close symbiotic relationship with L.chinensis,and thereafter improve the growth of L.chinensis in halophytic environment.Based on the understanding of the ecological functions of arbuscular mycorrhizal fungi that enhance plant tolerance,this study studied the effect of symbiotic relationship between plant and AM fungi on plant salt tolerance,and the effect of soil nutrient on symbiotic relationship between plant and AM fungi and its indirect effects on plant salt tolerance using pot experiment during two growing seasons.Main conclusions were obtained as follows:(1)Salt stress significantly reduced the growth of L.chinensis.Salt stress significantly decreased the aboveground and belowground biomass of L.chinensis and shifted the biomass allocation.However,the effect of salt stress on the belowground biomass was greater than the aboveground biomass.Salt stress decreased the rhizome and fibrous root biomass of L.chinensis,whereas the effect on fibrous root biomass was stronger than that on rhizome.In addition,salt stress reduced the reproduction potential,relative height growth rate and specific leaf area of L.chinensis.(2)AM fungi promoted the growth of L.chinensis,but the positive effect of AM fungi was reduced by salt stress.AM fungi increased the growth of fibrous root,relative height growth rate and the biomass accumulation of L.chinensis.But the effect of AM fungi was not significant under salt stress.The relative height growth rate of L.chinensis was significantly increased by AM fungi before the beginning of salt treatment but it decreased after salt stress.(3)The effect of nitrogen addition on the growth of L.chinensis was influenced by AM fungi.Nitrogen addition could significantly increase the growth of the rhizome,reproduction potential,relative height growth rate and the biomass accumulation of L.chinensis when the presence of AM fungi.But salt stress reduced the interactive effect between AM fungi and nitrogen addition.(4)The root architecture of L.chinensis was affected by salt stress,AM fungi and soil nutrients.Salt stress significantly decreased the root length,surface area and volume of rhizome and fibrous root of L.chinensis.When the L.chinensis grown without salt stress,AM fungi increased surface area and volume of rhizome and fibrous root,nitrogen addition significantly increased the root length,surface area and volume of rhizome.Under salt stress,the effects of AM fungi and nitrogen addition on root architecture were reduced.(5)The symbiotic relationship between AM fungi and L.chinensis was weakened by nitrogen addition.When the L.chinensis grown without salt stress,nitrogen addition increased the percentage of AM fungi colonization,increased the percentage of Glomus mosseae and Glomus etunicatum colonization,decreased percentage of G and mix-inocula colonization.Under salt stress,nitrogen addition decreased the percentage of AM fungi colonization.Based on the above conclusions,we suggest that appropriate nitrogen addition can promote the growth of plants by improving the ecological effect of AM fungi in grassland management,however,in the habitats with certain saline-alkali stress,the effects of nitrogen addition and AM fungi were not obvious.This paper not only clarified the ways that AM fungi participate in and regulate the salt tolerance of L.chinensis and its response to soil nutrient,but also provided the basic experimental data and theoretical basis for the bioremediation of saline-alkaline grassland.It has important practical significance for vegetation restoration and reconstruction of degraded grassland.