Improving drought and salinity tolerance in barley by application of salicylic acid and potassium nitrate

Abstract Growth and physiological activities of barley ( Hordeum vulgare L. cv. Gustoe) grown in soil cultures were evaluated to recognize the ameliorative role of salicylic acid (SA) and KNO 3 against the negative effects of salt and water deficit stresses. Barley plants were subjected to three levels of NaCl (50, 100 and 150 mM), three levels of water stress (80%, 70% and 50% of the soil water content (SWC) and the combination of 150 mM NaCl + 50 μM SA, 150 mM NaCl + 10 mM KNO 3 , 50% SWC + 50 μM SA and 50% SWC + 10 mM KNO 3 for two weeks. Salt and water deficit stresses reduced the shoot growth, leaf photosynthetic pigments, K + contents and provoked oxidative stress in leaves confirmed by considerable changes in soluble carbohydrate, proline, malondialdehyde (MDA), total phenolic compounds, antioxidant activity and Na + contents. Leaf soluble protein of salt and water deficit treated plants was unaffected. The Na + /K + ratio increased with increasing salt and water deficit treated plants. Application of 50 μM SA or 10 mM KNO 3 to150 mM NaCl and/or 50% SWC treated plants improved these attributes under salt and water stresses. Soluble carbohydrates in stressed plants may have a significant role in osmotic adjustment. It can be concluded that the addition of SA or KNO 3 can ameliorate the oxidative stress in barley stressed plants. This ameliorative effect might be maintained through low MDA contents and decreased Na + /K + ratio in leaves. This study also provided evidence for the ability of barley cultivation in salt and water deficit soils due to its capacity for osmotic adjustment.