Foliage applied proline induces salt tolerance in chili genotypes by regulating photosynthetic attributes, ionic homeostasis, and antioxidant defense mechanisms

Globally, soil salinity is a serious threat to horticultural crop productivity. Chili (Capsicum annumL.) is a major spice horticultural crop. Its growth and production is severely affected by salt stress. To address this problem, a sand culture experiment was conducted in which two contrasting chili genotypes 'Plahi' (salt tolerant) and 'A-120' (salt sensitive) were grown under salt stress (50 mM NaCl) with foliar application of proline (0.8 mM). Proline application enhanced salt tolerance in both genotypes by osmoregulation of sodium and potassium. It enhanced chili growth and fruit yield by improving plant water relations and gas exchange attributes under salt stress. Antioxidants were increased with proline application under salt stress. There was also a significant positive correlation found among glycinebetaine and proline contents. In conclusion, protein-treated chili plants performed better than untreated plants as evidenced by normal function of photosynthetic machinery and antioxidant mechanisms under salt stress.