Mechanisms of silicon-mediated alleviation of heavy metal toxicity in plants: A review

• Heavy metal toxicity in plants needs to address worldwide on priorities.
• Si has been considered to alleviate heavy metal toxicity in plants and soils.
• Si reduced the bioavailability of heavy metals in soil and uptake in plants.
• This review discussed all mechanisms induced by Si in plants against heavy metal toxicity.
• We reviewed most experiments that utilized the Si under metal toxicity in plants.

In present era, heavy metal pollution is rapidly increasing which present many environmental problems. These heavy metals are mainly accumulated in soil and are transferred to food chain through plants grown on these soils. Silicon (Si) is the second most abundant element in the soil. It has been widely reported that Si can stimulate plant growth and alleviate various biotic and abiotic stresses, including heavy metal stress. Research to date has explored a number of mechanisms through which Si can alleviate heavy metal toxicity in plants at both plant and soil levels. Here we reviewed the mechanisms through which Si can alleviate heavy metal toxicity in plants. The key mechanisms evoked include reducing active heavy metal ions in growth media, reduced metal uptake and root-to-shoot translocation, chelation and stimulation of antioxidant systems in plants, complexation and co-precipitation of toxic metals with Si in different plant parts, compartmentation and structural alterations in plants and regulation of the expression of metal transport genes. However, these mechanisms might be associated with plant species, genotypes, metal elements, growth conditions, duration of the stress imposed and so on. Further research orientation is also discussed.