Arbuscular mycorrhizal fungi promote plant growth of Leymus chinensis (Trin.) Tzvelev by increasing the metabolomics activity under nitrogen addition

Abstract Nitrogen (N) deposition has been influencing ecological process, for instance N addition can affect plant growth and then alter plant community composition. Arbuscular mycorrhizal fungi (AMF) is one of the important soil microbiota, which play a key role in plant growth, especially under harsh environmental conditions. However, the effects of AMF on plant growth under N addition are still not well understood. To investigate the mechanism how AMF affect plant growth under N addition, a microcosm experiment was conducted with four N addition levels. The results showed that AMF increased aboveground biomass of Leymus chinensis by 21.5% and 4.8% under with and without N addition, respectively. AMF expressively improved the net photosynthetic rate by 44% and 29%, soluble protein by 65% and 40% under with and without N additions, respectively. The chlorophyll a, chlorophyll b, chlorophyll a + b and carotenoids content in leaves treated by AMF were greater than those without AMF treatment. AMF also significantly increased the metabolomics enzymes glutamate dehydrogenase, glutamine oxoglutarate aminotransferase, alanine transaminase and nitrogen reductase activity under N addition. However, the level of glutamine synthetase and soluble carbohydrates increased significantly under N addition in non‐inoculated AMF plants. The result showed that the response of AMF to L. chinensis was stronger than nitrogen deposition, which indicates that AMF could increase plant growth by improving photosynthetic characters and affecting metabolomics enzymes of L. chinensis under N addition.