Comparative efficacy of natural and synthetic silicon fertilizers in enhancing yield and mitigating heavy metals (Cd and Pb) toxicity by modulating antioxidant activity in wheat (Triticum aestivum L.)

Heavy metals contamination, particularly cadmium (Cd) and lead (Pb), poses a major threat to wheat productivity and human health. The comparative efficacy of natural and synthetic sources of Si fertilization to alleviate heavy metals stress in wheat remains largely unexplored. A pot study comprising thirteen treatments was designed under a completely randomized design (CRD) to assess the synthetic (Ca silicate) and natural (treated burnt rice husk) Si fertilizers in promoting the wheat growth and mitigating the adverse effects of heavy metals-induced toxicity. Five surface-sterilized seeds of wheat cv. Faisalabad-2008 were sown in pots under controlled conditions (25 °C temperature, 75% relative humidity and 16/8 h light/dark period) from sowing to maturity (170 days). Application of both Si sources considerably enhanced all the agronomic, physiological, and biochemical characteristics of wheat by reducing the adverse impact of heavy metals stress. However, in comparison, the synthetic Si (Ca silicate) fertilization proved superior, resulting in the greatest improvements in plant height (11.60%) and grain yield (12.84%), while marked reduction in Cd (15.53%) and Pb (10.02%) contents in shoot under heavy metals stress. Si application increased superoxide dismutase (SOD) and peroxidase (POD) activities and reduced the electrolyte leakage (EL) and malondialdehyde (MDA), demonstrating effective mitigation of the oxidative stress. The correlation analysis proved that the positive changes in agronomic characteristics caused by Si fertilization were highly correlated with lower heavy metals uptake and increased antioxidant activities. Collectively, both Si fertilizer sources significantly reduced the Cd and Pb toxicity, however, in comparison; the synthetic Si fertilizer was more effective in enhancing the wheat productivity under Cd or Pb stress than natural Si fertilizer.