Antioxidative Response of Quinoa Exposed to Iso-Osmotic, Ionic and Non-Ionic Salt Stress

Antioxidants play an important role in adapting plants to abiotic stress by detoxifying reactive oxygen species (ROS). Involvement of antioxidant enzymes in abiotic stress tolerance of highly stress-tolerant quinoa was studied in a climatic chamber at 6mOsm (milliosmolar) ionic (300mm NaCl) and non-ionic (600mm mannitol) salts combined with increasing levels of potassium K1 and K2 (6, 12mm), respectively. Fifteen days of salt treatment (both ionic and non-ionic) decreased plant growth (shoot and root fresh weight), stomatal conductance and chlorophyll content index. Furthermore, both forms of salt stress increased the activities of superoxide dismutase, catalase, ascorbate peroxidase and peroxidase up to 2.33-, 3.98-, 4.78- and 5.55-folds, respectively, compared to no salt treatment, whereas membrane stability index decreased corresponding to increase in lipid peroxidation (malondialdehyde), with salt treatments compared to non-stressed plants. However, no significant effect of potassium and salt treatments has been noticed on the maximal photochemical efficiency of PSII. The results suggested that enhanced antioxidant enzymes activity under salt stress could be one of the factors responsible for abiotic stress tolerance in quinoa.