Effect of Exogenous Chitosan on Physiological Characteristics, Photosynthetic Parameters, and Antioxidant Systems of Maize Seedlings Under Salt Stress

Salt stress has detrimental effects on crops. Chitosan (CTS), a biocompatible, nontoxic, and biodegradable copolymer, plays a multifaceted role in regulating plant stress adaptation. The root application of CTS demonstrates more efficient activation of antioxidant activity, thereby enhancing stress tolerance in plants compared to other methods. This study aimed to evaluate the role of root-applied CTS on the photosynthetic system and antioxidant defense mechanisms of maize seedlings under salt stress. A hydroponic experiment was conducted with the root application of six concentrations (0, 25, 50, 100, 200, 400 mg·L^− 1) of CTS under salt stress conditions (150 mM). The results revealed that CTS significantly improved biomass accumulation, tolerance index, root development, photosynthetic parameters, pigment contents, ascorbate (AsA) and glutathione (GSH) contents, antioxidant enzyme activities, and soluble protein content, while decreasing sodium (Na) absorption and malondialdehyde (MDA) levels in maize seedlings under salt stress. Partial least squares (PLS) analysis highlighted the pivotal roles of photosynthetic parameters and pigment contents in maize tolerance to salt stress. Furthermore, 100 mg·L^− 1 CTS demonstrated the most effective reduction in salt-induced oxidative damage, with a reduction of 39.48% in the leaf and 40.22% in the root, leading to significant increases in biomass accumulation (61.59% in the shoot and 39.61% in the root) and tolerance indexes (61.57% in the shoot and 39.59% in the root). Based on these results, it can be concluded that root application of CTS, particularly at 100 mg·L^− 1, can effectively alleviate the negative effects of salt stress on maize seedlings. This suggests that CTS can be an effective tool for enhancing stress tolerance in maize seedlings, potentially improving crop resilience in saline environments. Future research should focus on the long-term effects of CTS application in field conditions to determine the sustainability and practical applicability of CTS in various agricultural settings.