Silicon: A Crucial Element for Enhancing Heavy Metals Tolerance in Plants

The contamination of heavy metals (HMs) in agricultural soils is a serious concern for food safety and the environment globally. Excessive accumulation of HMs adversely affects seed germination and impairs physiological processes in plants; indirect effects mainly result from the production of reactive oxygen species (ROS) in vital plant tissues, leading to compromised human health via the food chain. Despite several approaches for mitigating the toxicity of HMs, silicon (Si) has emerged as a promising prospect for HM stress tolerance in plants. This review paper emphasizes the current knowledge on the role of Si in regulating the availability and uptake of HMs, with particular emphasis on plant and soil-related mechanisms. Si reduces HM bioavailability through adsorption, co-precipitation and immobilization in soil. However, Si restricts HM uptake in plants by regulating metal transporter-related genes, chelation, enhancing antioxidant defence, and physiological modifications. Moreover, the recent advances in Si nanoparticles (Si-NPs) further enhance their potential for strengthening the plant defence responses and improving HM immobilization, although their long-term environmental effects and field applicability remain insufficiently understood. Prospects should consider and focus on elucidating Si-HM interactions at the rhizosphere and molecular levels and establishing their environmental and food safety implications. This review provided a brief key step involved in the reduction of HM toxicity and detoxification of HMs through Si application. Overall, Si represents a promising and multifaceted approach for mitigating HM toxicity and improving crop resilience in contaminated agricultural systems.