Effects of jasmonic acid pretreatment on perennial ryegrass seed germination under heat stress

Using perennial ryegrass varieties ‘Mathilde’ and ‘Esquire’ as test materials, we evaluated the effects of different temperatures (20, 25, 30, and 33 ℃) and jasmonic acid concentrations (5, 10, 20, 40, 60, 80, and 100 μmol·L^–1) on the seed germination of perennial ryegrass. To a certain degree, the results demonstrated that high temperature stress affected the germination characteristics of perennial ryegrass seeds. The germination rate, germination potential, and germination index of perennial ryegrass seeds decreased significantly with increasing temperature, especially affecting root and seedling length. Notably, the germination characteristics of ‘Mathilde’ were better than ‘Esquire.’ Under high temperature stress, the germination ability of perennial ryegrass seeds was significantly improved by soaking seeds in jasmonic acid concentrations between 40 and 60 μmol·L^–1. Meanwhile, the superoxide dismutase (SOD) activity of the seedling significantly increased while the malonic dialdehyde (MDA) content decreased. Treatment with an appropriate concentration of jasmonic acid could efficiently improve the germination ability and activity of perennial ryegrass seeds under heat stress.