Sodium Chloride-Induced Changes in Mineral Nutrients and Proline Accumulation in Indica Rice Cultivars Differing in Salt Tolerance

The effect of increasing sodium chloride (NaCl; 0 to 300 mM) stress was investigated on plant growth, mineral nutrients, and proline accumulation in two indica rice cultivars differing in salt tolerance. The shoots and roots of 'Karjat-3' (salt sensitive cv.) showed greater reduction in fresh weight, dry weight, and water content under increasing salinity stress when compared to 'Panvel-3' (salt tolerant cv.). The magnitude of chloride (Cl) accumulation with increasing salinity varied between cultivars, with lesser accumulation in 'Panvel-3', whereas, calcium (Ca) content was more in 'Panvel-3' than 'Karjat-3' at all salinity levels. Increase in shoot-sodium (Na) did not show notable variation between cultivars under salinity stress; however, Na accumulation was notably lower in roots of 'Panvel-3' than 'Karjat-3'. Under increasing salinity stress, 'Panvel-3' maintained significantly lower sodium/potassium, sodium/calcium and sodium/nitrogen ratios than 'Karjat-3', both in shoots and roots, with more differential response in roots. Regardless of treatment, proline concentration was considerably higher in 'Panvel-3' than in 'Karjat-3'. The salt tolerance of cv. 'Panvel-3' was positively correlated with better growth, higher proline accumulation and enhanced uptakes of beneficial minerals such as potassium (K) and Ca.