Effects of earthworm (Eisenia fetida) and arbuscular mycorrhizal fungi improving plant hormones and antioxidant enzymes under simulated acid rain stress

Abstract

Acid rain is considered one of the three most serious environmental disasters worldwide, disrupting the normal physiological metabolism of plants and inhibiting their growth. Earthworms alleviate plant stress by regulating soil physical, chemical and biological characteristics, and mycorrhizal fungi can promote plant nutrient absorption and improve plant resistance via symbiosis with plants. We used Illumina high-throughput sequencing to conduct a relevant redundancy analysis (RDA) of soil microbial community structure and plant growth factors, and we constructed a structural equation model (SEM) 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. The results showed that earthworms promoted the decomposition of soil organic matter; promoted the growth of the root system; and increased the hormone levels of gibberellin A3 (GA3), abscisic acid (ABA) and indole-3-acetic acid (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 and alleviated the simulated acid rain stress of the aboveground part of the maize. This funding is crucial to understanding above- and belowground feedback in plant–soil systems under abiotic stress.