Nano-silica modulates salt stress response in lettuce by enhancing growth, antioxidant activity, and mineral uptake

Salt stress is a significant abiotic factor that limits crop growth and yield. Nano-fertilisers, effective even in small quantities, have gained prominence for their ability to enhance plant growth and stress tolerance. This study investigated the effects of silica nanoparticles (SiNPs) at different concentrations (0, 100, 200, and 400 mg/L solution) under varying saline water application levels (0.6, 1.2, 2.4, and 3.6 dS/m) on growth parameters, antioxidant enzyme activity, and nutrient uptake in lettuce. The greenhouse experiment followed a randomised complete block design with three replications. Results demonstrated that SiNPs effectively increased head diameter and plant height by approximately 8% and 14%, respectively, compared to the control. Similarly, dry matter content improved by 22% with SiNP-400. While salinity stress significantly increased electrolyte leakage and lipid peroxidation (as indicated by malondialdehyde (MDA) content), SiNPs reduced MDA levels by 21%, indicating lower oxidative damage. Soil-plant analysis development (SPAD) values improved by 6%, and leaf relative water content increased by 4% with the application of SiNPs. Enzyme activity analysis revealed that salinity stress enhanced superoxide dismutase (SOD) and catalase (CAT) activities, but SiNP-400 reduced SOD and CAT levels by 23% and 50%, respectively, suggesting a decrease in oxidative stress. Furthermore, SiNPs enhanced nutrient uptake, significantly increasing the contents of Mg, Fe, and Zn while reducing Na accumulation. The highest Mg, Zn, and K concentrations were recorded under the SiNP-400 treatment. These findings highlight the potential of silica nanoparticles in mitigating the effects of salt stress and improving plant resilience, highlighting their role in sustainable agriculture.