To investigate the physiological regulation mechanisms of plant growth-promoting bacteria on the drought， cold， and saline-alkali stress tolerance of perennial ryegrass （Lolium perenne L.）， this study used Bacillus paralicheniformis （NCBI ID： PRJNA1402526） as the test strain. A pot inoculation experiment was conducted under three abiotic stress conditions-drought， cold， and saline-alkali stress—to analyze the effects of rhizosphere inoculation on the growth indices， physiological characteristics， and root morphology of perennial ryegrass. The results showed that inoculation with B. paralicheniformis significantly alleviated the growth inhibition caused by abiotic stresses. Compared to the non-inoculated control， the inoculated plants exhibited significantly increased plant height， above-ground and below-ground biomass， along with markedly reduced leaf relative conductivity and malondialdehyde content. Additionally， the activities of superoxide dismutase， peroxidase， and catalase， as well as the contents of proline and soluble sugars， were significantly enhanced （P<0.05）. Moreover， root system architecture was notably improved. In conclusion， inoculation with B. paralicheniformis can significantly enhance the resistance of perennial ryegrass to drought， cold， and saline-alkali stresses by synergistically strengthening its antioxidant defense capacity， osmoregulatory function， and root morphological configuration.

Bacillus paralicheniformis  /  Perennial ryegrass  /  Abiotic stress  /  Antioxidant enzymes  /  Osmotic regulation  /  Root morphology