Silicon nanoparticles mitigate photochemical and oxidative imbalances induced by magnesium deficiency in bell pepper plants

Magnesium (Mg) deficiency is common in agricultural systems and causes biological disturbances that limit bell pepper ( Capsicum annuum L.) production; however, studies elucidating these damages and, especially, sustainable strategies to mitigate this stress remain scarce. This study investigated whether the application of silicon nanoparticles (nSiO 2 ) can alleviate the physiological and biochemical impairments induced by Mg deficiency and optimize plant performance under adequate nutrition. Plants were grown in nutrient solution under two Mg levels (deficient: 0 mmol L⁻¹; sufficient: 1.6 mmol L⁻¹), combined with the absence (0 mmol L⁻¹ Si) or presence of nSiO 2 (2.0 mmol L⁻¹ Si). Mg deficiency drastically reduced nutrient concentration and accumulation, increased cellular electrolyte leakage, and promoted chlorophyll and pheophytin degradation, thereby decreasing the maximum quantum efficiency of photosystem II (F v /F m ), growth, and biomass accumulation. nSiO 2 supply mitigated these negative effects by reducing cellular electrolyte leakage, increasing phenolic compounds and ascorbic acid contents, and improving photochemical efficiency, even without restoring Mg levels. Under Mg sufficiency, nSiO 2 acted as a biostimulant, enhancing pigment accumulation, antioxidant capacity, and dry biomass. Multivariate analysis revealed that nSiO 2 modulated the patterns of Mg-deficient plants, making them resemble those observed under adequate nutrition. These findings demonstrate that nSiO 2 functions both as a stress-mitigating agent and as a metabolic enhancer, preserving photochemical and redox stability in Mg-deficient plants and promoting performance under optimal nutritional conditions. This study provides the first comprehensive assessment of the impacts of nSiO 2 on bell pepper cultivation under both limiting and non-limiting Mg conditions, supporting the expanded use of this beneficial element to strengthen sustainable production of this species.