Enhancement in Okra (Abelmoschus esculentus) Growth Performance Under Salt Stress Using Exogeneous Application of L- tryptophan

Salinity is one of the major stress factors that has a substantial impact on agricultural resilience and concerns global food safety. L-tryptophan being an essential regulator with specialized activities in plant functioning, as well as an increase in tolerance to various abiotic stressors. A hydroponic experiment was carried out to determine the effective role of L-tryptophan in okra seedlings in saline environment in terms of growth, physiological, ionic, and antioxidant properties. Salinity was imposed in growth medium with two levels of NaCl (Control and 80 mM NaCl) whereas one level of L-tryptophan (50 µM L-1) administered externally in both combined and single forms. MDA and H2O2 contents increase while plant dry matter, chlorophyll content, relative water contents, membrane stability index, K+/Na+ ratio decreases due to salt stress. Salt toxicity was reduced when L-tryptophan was added as illustrated by increased relative water contents, membrane stability index, K+/Na+ ratio, as well as suppression of MDA and H2O2 generation. Our findings suggested that L-tryptophan increased salinity tolerance in okra, which could be a cause of viable sustainable production from salt-affected soils.