Abstract: Hydroponic experiments were conducted to study the effects of exogenous nitric oxide (NO) donor sodium nitroprusside (SNP) on the growth and root reactive oxygen species metabolism in ryegrass (Lolium perenne L.) seedlings under 300 μmol·L^-1 LaCl₃ stress. The results showed that under the stress, spraying 50 μmol·L^-1 SNP significantly inhibited the transportation of lanthanum (La) from root to shoot in ryegrass seedlings, alleviated the inhibition effect of La on the seedlings growth, increased the activities of superoxide dismutase and ascorbate peroxidase, significantly decreased peroxidase activity, the contents of reduced glutathione, proline, H₂O₂ and malondialdehyde, and O₂^-· production rate as well as plasma membrane relative permeability in the seedling roots, but had no effect on catalase activity and ascorbic acid content. The results indicated that NO could alleviate the growth inhibition of ryegrass seedlings caused by high concentration La stress via adjusting the root reactive oxygen species metabolism.

Key words: nitric oxide, lanthanum, seedling growth, reactive oxygen species, ryegrass