Earthworm and Arbuscular Mycorrhizal Fungi Improve Plant Hormones and Antioxidant Enzymes to Alleviate Simulated Acid Rain Stress

Abstract Aims Acid rain is considered one of the three most serious environmental disasters worldwide, disrupting the normal physiological metabolism of plants and inhibiting their growth. As important parts of soil biota community, both earthworms and arbuscular mycorrhizal fungi can promote the growth of plants under adverse conditions. However, whether them can improve the stress tolerance of plants under simulated acid rain stress remains to be explored.Methods Illumina high-throughput sequencing was used to conduct a relevant redundancy analysis (RDA) of soil microbial community structure and plant growth factors, and a structural equation model (SEM) was constructed for maize biomass and a biological index to study the mechanisms by which earthworms and mycorrhizal fungi affect maize stress resistance under simulated acid rain stress. Results Earthworms promoted the absorption of soil organic matter by maize; promoted the growth of the root system; and increased the hormone levels of GA3, ABA and IAA; ultimately improving the stress resistance of maize. Mycorrhizal fungi increased the relative abundance of plant growth-promoting rhizosphere bacteria, increased the levels of plant hormones and antioxidant enzymes, and improved the stress resistance of maize. Earthworms promoted infection by mycorrhizal fungi, and the interaction between earthworms and mycorrhizal fungi increased the root IAA content and the Shannon index of rhizosphere bacteria.Conclusions Both earthworms and mycorrhizal fungi can improve the stress resistance of maize through underground regulation. They interacted in increasing the root IAA content and the Shannon index of rhizosphere bacteria and alleviated the simulated acid rain stress of the aboveground part of the maize.