Exogenous application of gibberellic acid and ascorbic acid improved tolerance of okra seedlings to NaCl stress

Accumulation of salts in soils has become a serious environmental threat for plant growth and causes considerable loss in yield. Okra Abelmoschus esculentus L. is an important crop and sensitive to saline stress. In the present study, to explore methods for growing okra in salty area, exogenous gibberellic acid (GA3) and ascorbic acid (AsA) were foliage applied on okra seedling under NaCl stress. The results showed that treatment with 100 mM NaCl decreased shoot length, root length, fresh weight, dry weight, contents of chlorophyll pigments and nutrient elements, enhanced levels of electrolyte leakage, H2O2, lipid peroxidation and activities of antioxidant enzymes. Treatments with 0.1 mM GA3 and/or 0.1 mM AsA could alleviated harmful effects of saline stress on okra seedlings by improving growth indicators, increasing contents of chlorophyll and carotenoids, stimulating activities of antioxidant enzymes and decreasing electrolyte leakage, H2O2 content and lipid peroxidation. Moreover, concentrations of K, Ca, Mg and Fe in leaves and roots as well as levels of osmo-protectants (proline and soluble protein) increased in response to treatment with GA3 + AsA in NaCl-stressed okra seedling. Overall, foliar application of GA3 and/or AsA demonstrated benefits to okra seedlings in salty environments. Combined application of GA3 and AsA was more effective than sole use of GA3 or AsA alone.