Co-application of potassium and thiourea for mitigating salinity stress in wheat seedlings

Salt stress disrupts ionic homeostasis and induces oxidative damage, leading to reduced plant growth and development. Determining the lethal dose of NaCl is essential for developing effective mitigation strategies. Potassium and other antioxidant regulatory compounds often prove insufficient in addressing salt-induced toxicity, especially in wheat. This laboratory experiment aimed to determine NaCl concentration that reduces plant growth by 50% and to evaluate the effectiveness of different mitigation approaches involving potassium and thiourea supplementation at 0 mM, 10 mM, and 15 mM under the identified NaCl condition. The experiment followed a factorial arrangement with three biological replications. Results showed that NaCl at 198 mM decreased germination and plant growth by 50%. The combined application of potassium and thiourea at 15 mM significantly improved ionic homeostasis, leading to a 14% increase in overall ion balance. This was achieved by reducing sodium ions concentration by 28.55% and increasing potassium ion concentration by 23.92%. Furthermore, the interactive application enhances various growth parameters, including shoot and root length (by 14.20-32.82%), and shoot/root fresh and dry weight (by 18.56/8.89% to 26.60/25.52%, respectively). These improvements were attributed to enhanced physiological processes, including a 10.23% increase in net photosynthetic rate, a 30.20% increase in stomatal conductance, a 6.70% increase in transpiration rate, an 8.12% increase in internal carbon dioxide concentrations and a 10.13% improvement in relative water content. Additionally, oxidative markers, such as hydrogen peroxide and malonaldeahyde, were reduced by 8.43% and 26.20%, respectively. This reduction was associated with increased antioxidant enzyme activity, including a 13.69% increase in superoxide dismutase, an 8.91% increase in catalase, a 20.18% increase in peroxidase, and a 13.11% increase in ascorbate peroxidase. The decrease in oxidative stress contributed to an 8.48% improvement in membrane stability and a 17.06% enhancement in relative water content. Principle component analysis confirmed the efficacy of the K15 + TU15 treatment in improving wheat salt tolerance. The simultaneous application of K and TU at 15 mM effectively mitigated salt-induced toxicity by enhancing ionic homeostasis and reducing oxidative stress through increased antioxidant enzyme activity in wheat.