Abstract: Effects of exogenous nitric oxide (NO) on root growth and its oxidative damage in rye grass (Lolium perenne L. caddieshack) seedlings under NaCl stress were studied. The results showed that with its concentration at 5~100 μmol·L^-1 sodium nitroprusside(SNP), an NO donor, could significantly alleviate the inhibitory effect of seedlings root Growth under 100 mmol·L^-1 NaCl stress, and 50 μmol·L^-1 SNP was most effective, but inhibited the root growth at 150 μmol·L^-1 or higher. SNP at 50 μmol·L^-1 raised the activities of superoxide dismutase (SOD), catelase (CAT), peroxidase (POD) and ascorbate peroxidase (APX), tonoplast H⁺-ATPase and H⁺-PPase of root- tips of rye grass seedling under 100 mmol·L^-1 NaCl stress, increased the contents of glutathione (GSH), ascorbic acid (ASA) and proline, K⁺/Na⁺ and (Spd+Spm)/Put ratio, and dry matter accumulation, respectively, reduced the contents of O^-₂, H₂O₂ and malondiadehyde (MDA), while the effect wasn’t distinct when treated with 1 mmol·L^-1 NO scavenger(2-phenel-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, PTIO) and 1 mmol·L^-1 NaNO₂ (as control). The above results suggested that NO could attenuate the root growth inhibition and its oxidative damage caused by salt stress through increasing antixoidative and osmotic adjustment capabilities, accelerating the selective uptake of root to K⁺ and the transformation Put into Spd and Spm, and decreasing Na⁺ uptake and enhancing compartmentalization of Na⁺ in vacuole.

Key words: nitric oxide, salt stress, rye grass, root, oxidative damage, polyamine