Journal of Plant Process and Function

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Salt stress is one of the most important abiotic stresses which severly affects agriculture in the world. One of the strategies to deal with this stress is to investigate the mechanisms of tolerance in halophyte plants and to use them for crop improvement. The halophyte plant “Aleuropus littoralis” can tolerate salinity levels up to 600 mM. In this study, in order to investigate the mechanism of the antioxidant response of this plant to salinity stress, one-month seedlings were irrigated with Hoagland solution containing 0, 200 and 400 mM NaCl to induce salt stress. After 72 hours, root, stem and leaf tissues were sampled and the response of each tissue to salinity stress was evaluated. The results were compared using Duncan's multiple range test (p<0.05) after ANOVA. With increasing level of stress, protein content in all three tissues increased significantly. The amount of H₂O₂ in stem and root decreased with increasing salt concentration, but increased at 200 mM salt concentration. Based on the results, the general pattern of change in the activity of antioxidant enzymes was different in response to salt stress. The activity of superoxide dismutase in all studied tissues increased significantly with increasing stress level, so that the highest activity of the enzyme was observed in stem tissue and at 400 mM salt concentration (3.7 times more than the control). However, the changes in the activity of catalase and guaiacol peroxidase showed a decreasing trend or no significant change, so that the catalase activity in the leaf and at 400 mM salt concentration was almost half of the control and in the root more than half of the control. Finally, with increasing levels of stress, significant increase in ascorbate peroxidase activity was observed in all treatments, except in root tissue and 200 mM salt concentration. In general, according to the results, it can be stated that the balance between the antioxidant defense indices leads to the maintenance of destructive molecules such as H₂O₂ at a minimal level and plays an effective role in salinity stress tolerance in the A. littoralis.

Keywords: Ascorbate peroxidase, Hydrogen peroxidase, Superoxide dismutase, Catalase, Guaiacol peroxidase

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