The Effect of Arbuscular Mycorrhizal Fungi on Photosystem II of the Host Plant Under Salt Stress: A Meta-Analysis

As important components of the photosynthetic apparatus, photosystems I (PS I) and II (PS II) are sensitive to salinity. Salt stress can destroy the PS II reaction center, disrupt electron transport from PS II to PS I, and ultimately lead to a decrease in the photosynthetic capacity of the plant. Arbuscular mycorrhizal fungi (AMF) can enhance the photosynthetic capacity of a host plant under salinity stress. However, this specific effect of AMF is not always predictable. Here, we conducted a meta-analysis including 436 independent observations to compare chlorophyll fluorescence parameters in response to AMF inoculation under salt stress. The results showed that AMF inoculation had a positive total impact on photosynthesis in the host plant. Subgroup analysis showed that annual host plants had better performance in terms of photosynthesis after inoculation. The mitigating effects of AMF on the photosynthetic rate (Pn), actual quantum yield of photochemical energy conversion in PS II (PS II), and electron transfer rate (ETR) in C4 species were higher than those in C3 species. Moreover, the photosynthesis performance of monocotyledon species was better than that of dicotyledon species after AMF inoculation. The woody host plants had higher energy utilization by way of an enhanced electron transfer rate to reduce energy dissipation after AMF inoculation. Finally, the mitigating effect of AMF on plants under moderate salinity was stronger than that under high salinity. Among AMF species, Funneliformis mosseae was found to be the most effective in enhancing the photosynthesis performance of plants. For the analyzed dataset, AMF inoculation alleviated the detrimental effects of salinity on photosystem II of the host plant by improving the utilization of photons and photosynthetic electron transport, and also by reducing the susceptibility of photosystem II to photoinhibition.