Alleviation of cold stress impacts on grapes by the chitosan-salicylic acid nanocomposite (CS-SA NCs) application

Low temperature is a major abiotic stressor that limits the distribution of various fruit tree species worldwide. In this study, the effects of chitosan-salicylic acid nanocomposite (CS-SA NCs) treatment were evaluated on antioxidant enzyme activity, the antioxidant pool, and membrane stability indices in the grapevine cultivar 'Flame seedless' under cold stress conditions. Prolonged exposure to cold, compared to the control, led to a reduction in maximum fluorescence (Fm), variable fluorescence (Fv), the ratio of photochemical to non-photochemical use of light energy in photosystem II (Fv/F0), and the ratio of variable fluorescence to maximum fluorescence (Fv/Fm). Levels of chlorophylls, carotenoids, total soluble protein content, antioxidant enzyme activity, ascorbate, and glutathione activity significantly decreased with increasing cold stress duration. Electrolyte leakage, malondialdehyde, and hydrogen peroxide content increased by 75%, 60%, and 80%, respectively, after 16 hours of cold stress compared to the control. Nanocomposite treatment significantly enhanced antioxidant activity and stabilized membranes under cold stress by reducing electrolyte leakage and malondialdehyde release. Overall, CS-SA NCs act as a biological stimulant and can be effectively used to improve the physiological and biochemical responses of grapevines under cold stress. Further research is needed to gain a comparative understanding of various physiological responses, which will help guide the application of this nanocomposite in extension services and field production systems.