interactive influence of silicon and salicylic acid on physiological and biochemical responses of cucumber seedlings to salt stress

This study evaluated the interactive effects of silicon (si; 1.5 mm) and salicylic acid (sa; 10 and 15 µm) on cucumber (cucumis sativus l.) seedlings under non-saline and saline (80 mm nacl) conditions using a factorial experimental design. in saline and non-saline condition, significant si × sa interactions were detected for most growth, physiological, and biochemical traits. under non-saline conditions, the si + sa10 interaction increased leaf area, shoot dry mass, and total chlorophyll by 8–17% relative to the control, whereas si + sa15 showed minimal effects. under salinity, interaction effects were markedly amplified: compared with the control, si + sa10 increased leaf area by 40%, shoot dry mass by 57%, total chlorophyll by 44%, carotenoids by 61%, and shoot k⁺ content by 62%, while reducing shoot na⁺ accumulation by 36%. oxidative stress markers were strongly suppressed by the interaction, with reductions of 61% in malondialdehyde, 50% in hydrogen peroxide, and 50% in ion leakage. although antioxidant enzyme activities were not further enhanced by the interaction, si + sa10 significantly increased non-enzymatic antioxidants, including phenolics (58%), flavonoids (30%), and anthocyanins (49%), and substantially elevated shoot si accumulation. in contrast, the si + sa15 interaction produced consistently weaker responses. these findings demonstrate that salt tolerance in cucumber is maximized through a concentration-dependent interaction between silicon and salicylic acid, with low-dose sa synergistically enhancing si-mediated protection primarily via improved ion balance and non-enzymatic antioxidant defense.