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Salt stress significantly impairs plant growth and productivity. This study evaluated the effects of foliar-applied chitosan on salt stress mitigation in Brassica napus L. under NaCl treatments (0, 50, 100, 150 mM). Plants were treated with chitosan (0, 5, and 10 mg/L), and their physiological, biochemical, and molecular responses were analyzed. Chitosan at 10 mg/L significantly improved biomass production, root development, and photosynthetic efficiency, increasing total chlorophyll content by up to 35% under severe salinity (150 mM NaCl). It enhanced ion homeostasis by reducing sodium (Na+) accumulation (up to 19%) and increasing potassium (K+) uptake (up to 27%), mitigating ion toxicity. Chitosan at 10 mg/L also improved membrane stability and osmotic adjustment by elevating phenolics (47%), flavonoids (40%), and anthocyanins (60%), particularly under 100 and 150 mM NaCl. Antioxidant defense mechanisms were strengthened, with 10 mg/L chitosan increasing superoxide dismutase (SOD) activity by 15%, ascorbate peroxidase (APX) by 35%, and catalase (CAT) by 168%, leading to a 30% reduction in hydrogen peroxide (H2O2) content, primarily under high salinity (100–150 mM NaCl). Additionally, chitosan upregulated the expression of stress-related genes, including SOD (55%), APX (26%), and phenylalanine ammonia-lyase (PAL) (45%), reinforcing the oxidative defense system. These findings highlight chitosan’s role in salt tolerance via ion regulation, osmolyte synthesis, and antioxidant modulation, with 10 mg/L being the most effective concentration. Chitosan represents a promising biostimulant for enhancing crop resilience in saline environments. Future research should optimize formulations for large-scale applications and assess long-term effects on soil and plant health.
Soostani et al. (Wed,) studied this question.