Effects of Arbuscular Mycorrhizal Fungi on the Growth and Physiological Performance of Sophora davidii Seedling Under Low-Phosphorus Stress

Sophora davidii is a multipurpose, nitrogen-fixing shrub species. Phosphorus deficiency in the acidic soil of Southwest China has seriously affected its survival and growth, especially in the seedling stage. Evidence suggests that arbuscular mycorrhizal fungi (AMF) may improve the stress tolerance of plants. However, there is limited information on the systematic effects of AMF on phosphorus deficiency in S. davidii seedlings. We investigated the effects of three phosphorus levels (0.5, 0.25, 0 mmol/L) and two mycorrhizal inoculation (with Funneliformis mosseae and without Funneliformis mosseae) treatments on the growth and physiological performance of S. davidii using factorial design. The results showed that low-phosphorus stress significantly limited the growth of S. davidii seedlings and negatively affected their physiological properties. However, inoculation with F. mosseae significantly improved the plant height and shoot dry weight, promoted root growth, increased chlorophyll contents and osmoregulation substance contents, increased protective enzyme activity, and significantly reducing the accumulation of malondialdehyde, alleviated oxidative stress induced by low-phosphorus stress, improved the IAA and GA(3) contents, and alleviated the negative effects of low-phosphorus stress. AMF-induced enhancement of aboveground growth and plant physiological characteristics is dependent on the P level and its impact on roots is regardless of phosphorus status. AMF inoculation significantly promoted the absorption of nitrogen and phosphorus in the roots (0.25- and 0-mmol/L treatments), thereby maintaining a higher biomass and relieving stress in S. davidii seedlings under low-phosphorus conditions. Our results demonstrated that AMF inoculation is useful for the promotion and cultivation of S. davidii in the karst area of Southwest China under low-phosphorus stress conditions.