Thiourea Priming Improves Salt Tolerance in Cotton (Gossypium hirsutum) by Modulating Gas Exchange, Antioxidant Defense System and Osmoprotection

Excessive salt is one of the many factors contaminating agricultural environments and reducing productivity. In the recent past, several strategies have been investigated to overcome yield losses due to salt stress. However, the effects of thiourea on the morphology, physiology, and yield of cotton plants, have not yet been clearly understood. Therefore, the experiment was done to estimate the effects of 10 and 20 mM thiourea application as pre-sowing seed treatment on the growth and antioxidative activities of two cotton varieties (FH-114 and FH-118) grown under normal (0 mM) and NaCl stress (150 mM). Salt stress significantly reduced the overall shoot length (47%), chlorophyll a and b (42%, 37%), CO2 assimilation rate (17%), stomatal conductance (29%), sub-stomatal CO2 concentration (30%) and seed weight (29%). On the other hand, salinity enhanced the superoxide dismutase (16%), peroxidase (34%), ascorbic acid (47%), glycine betaine (41%), H2O2 (24%) and malondialdehyde (33%). The 10 mM application of thiourea considerably enhanced plant growth and physiology under salt stress conditions but was more effective in improving the CO2 assimilation rate (37%), catalase (13%), superoxide dismutase (28%), ascorbic acid (33%), glycine betaine (67%), Ca2+ (57%) and K+ (64%) contents as compared to 20 mM thiourea. On the other side, the 20 mM application of thiourea was more effective in enhancing shoot length (45%), chlorophyll a and b (33%, 39%), stomatal conductance (42%), sub-stomatal CO2 concentration (41%), total soluble proteins (41%), peroxidase (46%), seed weight (40%), number of bolls (43%) and weight bolls (31%). This research offers significant insights into strategies for mitigating the adverse effects of salt stress on cotton, a crop of critical economic importance. Importantly, the differential effects of 10 mM and 20 mM thiourea application offer practical guidance for optimizing seed priming techniques to enhance stress resilience. Thus, this study contributes valuable knowledge toward sustainable cotton production under saline environments, offering a potential, low-cost agronomic solution to address soil salinization challenges and ensure crop productivity.