Thiourea-induced redox balance and ion dynamics in salt-stressed barley (Hordeum vulgare L.)

Thiourea (TU) plays an important role in mitigating the negative effects of salinity on plants by altering various biological mechanisms in plants. In this experiment, two barley varieties (Jau-17 and Pearl-21) were sprayed with TU (10 and 30 mM) under salt stress (120 mM). Various physiological and biochemical attributes were studied. The results showed that salinity reduced all growth parameters, photosynthetic attributes, organic osmolytes, K+ and Ca2+ contents, and increased antioxidants in both barley varieties. The salt-induced decrease in Na+ content led to a decrease in K+ and Ca2+ ratios. The foliar application of TU exhibited greater enhancement of growth parameters in cv. Pearl-21, except for root length, where Jau-17 exhibited greater growth. This application resulted in a reduction in the Na+/K+ ratio and an increase in the concentrations of photosynthetic pigments, organic osmolytes, antioxidants, potassium, and calcium. Among the cultivars, Pearl-21 (relatively salt-tolerant) displayed superior antioxidant activity compared to Jau-17 (relatively salt-sensitive). Overall, both barley varieties exhibited divergent responses across different parameters under both saline and non-saline conditions. Overall, the exogenous application of TU at a concentration of 30 mM was particularly more effective than the other levels used in mitigating oxidative stress and promoting salinity tolerance in both cultivars of barley.