Physiological evidence that Funneliformis mosseae combined with chitosan regulates the photosynthetic efficiency and endogenous hormones of Glycine max to promote plant growth

Abstract Soybean ( Glycine max (L.) Merr.) production is often constrained by soil degradation and environmental stress. To explore green and growth‐promoting pathways, this study systematically investigated the combined effects of inoculating arbuscular mycorrhizal fungi ( Funneliformis mosseae , FM) and exogenous chitosan (CTS) on G. max growth, physiology, and photosynthetic efficiency. Results showed that the FM and CTS combined treatment (FM + CTS) promoted the aboveground fresh weight and yield in G. max , increasing by 65.04% and 12.67%, respectively, compared to the control group (CK). It also elevated the levels of endogenous hormones (CTK, IAA, SLs) in the leaves and enhanced the activity of antioxidant enzymes (CAT, SOD, POD). In terms of photosynthetic performance, the FM + CTS treatment group showed increases in net photosynthetic rate (Pn), transpiration rate (Tr), and stomatal conductance (GH 2 O) by 43.39%, 120.61%, and 112.93%, respectively, compared to CK. Additionally, it improved the maximum photochemical efficiency of PSII (Fv/Fm) and the electron transport rate (ETR). The fitting of light response and CO 2 response curves showed that under FM + CTS treatment, the maximum net photosynthetic rate (Pnmax), maximum Rubisco carboxylation rate (Vcmax), and maximum electron transport rate (Jmax) all reached the highest levels. In summary, FM and CTS promoted G. max growth and development by regulating endogenous hormones, enhancing antioxidant defence capabilities, and optimizing the process of photosynthetic carbon assimilation. This provides systematic physiological evidence for elucidating the mechanisms of FM and CTS actions and lays a theoretical and practical foundation for developing a green G. max production technology system based on the combination of microbial and biostimulant treatments.