碱性盐胁迫下豆-禾混播植物生长和生理特征对AM真菌接种的响应OA

In order to explore the regulatory effect and mechanism of arbuscular mycorrhizal fungi(AMF)on the growth of legume-grass mixed plants under alkaline salt stress,a greenhouse pot experiment was conducted to explore the changes and relationships of key processes such as biomass,stress resistance physiology,nitrogen fixation and nitrogen fixation transfer of mixed alfalfa(Medicago sativa)and Leymus chinensis under the influence of alkaline salt(Na2CO3)stress and AMF inoculation.The results showed that Na2CO3 stress significantly reduced the aboveground biomass of M.sativa and L.chinensis and the total aboveground biomass of mixed sowing(P<0.05).The aboveground biomass of alfalfa and L.chinensis decreased by 26.5%and 20.0%,respectively,and the total aboveground biomass of the mixed sowing decreased by 24.4%.Under Na2CO3 stress,AMF inoculation alleviated the growth limitation of mixed-sown alfalfa and L.chinensis and increased the total aboveground biomass of the mixed-sown population by 32.0%(P<0.05).Na2CO3 stress decreased the shoot content of alfalfa by 25.94%and 18.83%(P<0.05)under non-inoculated and AMF conditions,respectively.The nitrogen content in the aboveground part of L.chinensis decreased by 14.43%and 7.92%(P<0.05),the symbiotic nitrogen fixation rate of alfalfa nodules decreased by 15.55%and 35.42%(P<0.05),and the symbiotic nitrogen fixation transfer rate of the aboveground part of L.chinensis decreased by 11.4%and 25.6%(P<0.05).The contents of proline,soluble sugar,and malondialdehyde;the activity of antioxidant enzymes;and the photosynthetic rate and phosphorus content of mixed plants were significantly decreased and increased by Na2CO3 stress and AMF inoculation,respectively.Changes in the photosynthetic rate and phosphorus absorption were primarily correlated with the growth and nitrogen utilization characteristics of the mixed plants.The results showed that Na2CO3 stress significantly inhibited the growth of alfalfa and L.chinensis.Due to the greater damage to photosynthesis and phosphorus absorption,the damage to alfalfa under Na2CO3 stress was significantly higher than that of L.chinensis.AMF inoculation effectively alleviated the growth inhibition of mixed plants under Na2CO3 stress;however,there were no interspecific differences in the regulation of AMF on the growth of alfalfa and L.chinensis.Na2CO3 stress increases the dependence of mixed-population plants,especially alfalfa,on soil nitrogen by limiting nodule nitrogen fixation and nitrogen fixation transfer in alfalfa.AMF inoculation can effectively increase the contribution of symbiotic legume nitrogen fixation to forage production,particularly important for improving the sustainability of nitrogen use in mixed grasslands under saline-alkali stress.