Thiourea and arginine synergistically preserve redox homeostasis and ionic balance for alleviating salinity stress in wheat

Plant growth regulators are cost-effective and efficient methods for enhancing plant defenses under stress conditions. This study investigates the ability of two plant growth-regulating substances, thiourea (TU) and arginine (Arg), to mitigate salinity stress in wheat. The results show that both TU and Arg, particularly when used together, modify plant growth under salinity stress. Their application significantly increases the activities of antioxidant enzymes while decreasing the levels of reactive oxygen species (ROS), malondialdehyde (MDA), and relative electrolyte leakage (REL) in wheat seedlings. Additionally, these treatments significantly reduce the concentrations of Na⁺ and Ca²⁺ and the Na⁺/K⁺ ratio, while significantly increasing K⁺ levels, thereby preserving ionic osmotic balance. Importantly, TU and Arg markedly enhance the chlorophyll content, net photosynthetic rate, and gas exchange rate in wheat seedlings under salinity stress. The use of TU and Arg, either individually or in combination, results in a 9.03-47.45% increase in dry matter accumulation, with the maximum increase observed when both are used together. Overall, this study highlights that maintaining redox homeostasis and ionic balance are crucial for enhancing plant tolerance to salinity stress. Furthermore, TU and Arg are recommended as potential plant growth regulators to boost wheat productivity under such conditions, especially when applied together.