Silicon enhances salinity tolerance in tomato (Solanum lycopersicum L.) through physiological, biochemical, and ionic regulation

Abstract Background Soil salinization poses a significant threat to agricultural production, necessitating innovative agronomic strategies to mitigate its impact. Salinity stress is a critical abiotic factor that hampers tomato growth by causing ionic imbalances, oxidative damage, and disruptions in physiological systems. This study investigated the effect of sodium silicate (Na₂SiO₃) in reducing salt stress in tomato plants exposed to 75 and 150 mM NaCl. Results The results indicated that salinity substantially decreased plant growth, the content of photosynthetic pigments, and the uptake of essential mineral nutrients. Concurrently, it heightened oxidative stress markers such as malondialdehyde (MDA), electrolyte leakage, hydrogen peroxide (H₂O₂), and hydroxyl radicals (•OH). Treatment with Na₂SiO₃, particularly at a concentration of 2 mM, significantly improved growth performance and photosynthetic pigment content. Silicon treatments enhanced the antioxidant defense mechanisms by increasing the activity of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR), and peroxidase (POX). Additionally, levels of ascorbate (AsA) and glutathione (GSH) were raised, leading to reduced oxidative damage and stabilized cellular membranes. The application of silicon also improved ionic homeostasis by decreasing sodium ion (Na⁺) concentration while enhancing the absorption of nitrogen (N), phosphorus (P), potassium (K⁺), and silicon. Conclusions In conclusion, the study demonstrated that silicon effectively alleviates salt stress in tomato plants by improving redox balance, enhancing antioxidant capacity, and regulating ion transport. The most effective concentration of Na₂SiO₃ was found to be 2 mM. The exogenous application of sodium silicate, especially at this concentration, helps to mitigate salinity-induced impairments in tomato plants by enhancing physiological performance, antioxidant defense, and ionic balance. This suggests its potential use as a sustainable agricultural strategy under salt-affected conditions.