Effect of nitric oxide on antioxidative responses under salinity conditions in Zygophyllum fabago L. (Zygophyllaceae)

In recent years, the involvement of nitric oxide (NO) in numerous physiological processes, particularly the mitigation of stress-induced negative effects on plants, has been clarified. Under salinity conditions, plants are subjected to a secondary oxidative stress. The present work was designed to examine the exogenous application of nitric oxide (NO), in the form of its donor sodium nitroprusside (SNP), in mitigating the deleterious effects of salinity on Zygoph-yllum fabago L. plants. SNP (200 µM) was applied to plants growing medium under saline (200 and 400 mM NaCl) and non-saline conditions. Growth, oxidative stress markers [cell membrane stability index (MSI) and H2O2 conc-entration], antioxidant enzymes activities [peroxidase (POX, EC 1.11.1.7) and catalase (CAT, EC 1.11.1.6)], as well as the contents of some antioxidant compounds (flavonoids and carotenoids) were determined. Salinity lowered the shoot and root dry weights, while it enhanced peroxidase and catalase activities. High salinity increased H2O2; however, it de-creased the carotenoids content of leaves. Exogenous NO enhanced the growth, MSI, flavonoids and carotenoids co-ntents of salinized plants. In salinity plus SNP treated plants, H2O2 concentration and the activities of the examined en-zymes were reduced. Data suggest that a cooperative process is performed by the antioxidant systems in Syrian bean ca-per in order to cope with salinity. Also, the application of exogenous NO was found to be useful in the mitigation of salinity-induced oxidative stress in plants.