Effect of arbuscular mycorrhizal fungi on alfalfa seedling growth at different soil pH

The present study was performed in a greenhouse to test the effects of arbuscular mycorrhizal fungi (AMF) on the growth of Medicago sativa (alfalfa) in the seedling stage under different soil pH. The plants were inoculated with Claroideoglomus etunicatum, Rhizophagus intraradices along with the mixture of two AMF fungi at three different soil pH values (6.48, 5.0, and 3.0). The results showed that with the reduction of soil pH, the plant height, leaf number, chlorophyll content, net photosynthetic rate, phosphorus absorption, and biomass of alfalfa were significantly reduced, whereas malondialdehyde (MDA) concentration was significantly increased. The presence of AMF alleviated the damage caused by acid stress on the plants. Compared to NM treatment, inoculation with AMF promoted plant growth, phosphorus absorption, and photosynthesis. Moreover, alfalfa colonized by AMF had a higher value of superoxide dismutase (SOD) enzyme activity and biomass, and a lower MDA concentration. The mixture of C. etunicatum and R. intraradices had the most significant positive effects on plant growth. The plant height, leaf number, chlorophyll content, net photosynthetic rate, total phosphorus content, and biomass of alfalfa were increased by 195.53%, 332.57%, 89.65%, 167.42%, 915.01%, and 97.7% (P < 0.05), respectively. In addition, the activity of SOD increased by 137.11% (P < 0.05) and the concentration of malondialdehyde (MDA) decreased by 47.15% (P < 0.05).