The photoprotective role of arbuscular mycorrhizal fungi (AMF) in cucumber seedlings under cold stress

The influence of symbiosis with arbuscular mycorrhizal fungi (AMF; Glomeromycota), Rhizophagus irregularis, on cucumber growth, the function of photosynthesis and biochemical stress markers was studied under cold stress. Cold stress reduced the photochemical quenching parameters, including the maximum photochemistry efficiency of photosystem II (Fv/Fm), the quantum yield of linear electron flux (ΦPSII), the efficiency of excitation capture by open PSII center (Fv'/Fm') and the coefficient of photochemical quenching (qP), but it elevated the nonphotochemical quenching (NPQ). AMF alleviated the damage of cold stress by decreasing the content of chlorophyll and H₂O₂ in plant leaves and reducing the root dry weight, net photosynthetic rate (Pn) and qP parameters. The NPQ parameters increased by cold stress, were also alleviated by AMF. Content of chlorophyll was increased in inoculation plants under cold stress, which also help the photosynthesis in inoculated plants. These results indicate that AMF can alleviate the growth inhibition caused by cold stress in a complex way, especially to protect photosynthesis system II and promote photosynthesis.