Exogenous nitric oxide protects against salt-induced oxidative stress in the leaves from two genotypes of tomato (Lycopersicom esculentum Mill.)

Nitric oxide (NO) has emerged as a key molecule involved in many physiological events in plants. To characterize roles of NO in tolerance of tomato (Lycopersicom esculentum Mill.) to salt stress, the protective effects of NO against salt-induced oxidative stress in the leaves of tomato cultivar Hufan1480 (salt-tolerant) and Hufan2496 (salt-sensitive) were evaluated. Under salt stress, Hufan1480 showed higher biomass accumulation, and less oxidative damage when compared with the Hufan2496. Application of exogenous sodium nitroprusside, a NO donor, dramatically alleviated growth suppression induced by salt stress in two tomato ecotypes, reflected by decreased malondialdehyde and O2·− production. Furthermore, the antioxidant enzymes superoxide dismutase, guaiacol peroxidase, catalase and ascorbate peroxidase, the antioxidant metabolites ascorbate and reduced glutathione, and the osmosis molecules proline and soluble sugar were increased in both ecotypes in the presence of NO under salt stress. Therefore, the protective effect of NO against salt-induced oxidative damages in tomato seedlings is most likely mediated through stimulation of antioxidant system.