Silicon elevated cadmium tolerance in wheat (Triticum aestivum L.) by endorsing nutrients uptake and antioxidative defense mechanisms in the leaves

Numerous abiotic stressors including heavy metal stresses, specifically cadmium (Cd) stress in agricultural bio-system hinder the plant adequate growth. The present study was aimed to reveal the protective role of silicon (Si) application with two levels and to recognize the optimum level of Si for wheat plants grown hydroponically under three different levels of Cd toxicities. In methodology, we used nine treatments with three levels of Si (0, 1, and 3 mmol L⁻¹; Na₂SiO₃) against three levels of Cd (0, 50, 200 μmol L⁻¹; CdCl₂) with three biological replicates. The results of our study demonstrated that Si incorporation with the advantage of 3 mmol L⁻¹ in cultured media with Cd50 and Cd200 demolished the toxic effects of Cd on the leaves of wheat plants by increasing plant dry biomass by 88% and 262%, leaf area by 48% and 57%, total chlorophyll contents by 120% and 74%, catalase (CAT) activity by 92% and 110%, superoxide dismutase (SOD) activity by 62% and 78%, peroxidase (POD) activity by 66% and 40%, ascorbic acid (AsA) contents by 33% and 34%, glutathione (GHS) contents by 39% and 30% and reduced MDA contents by 56% and 50%, H₂O₂ contents by 61% and 66%, and EL contents by 56% and 47% as parallel to Cd corresponding levels. In addition, Si incorporation with the advantage of 3 mmol L⁻¹ significantly increased relative water contents (RWC) to maintain the cell turgor pressure and protect the plant from wilting and cells flaccid and enhanced membrane stability index (MSI) to protect the plant from logging under damaging effects of Cd toxicities. Based on the present findings, Si can be considered a quasi-essential element that enhanced wheat tolerance against Cd toxicity by limiting uptake, accumulation, and translocation of Cd and through regulating antioxidative defense mechanisms.