Influence of Silicon on Translocation, Compartmentation and Uptake of Lead in Leafy Vegetables

Abstract

Lead (Pb) has phytotoxic and toxic effects on plants and animals. Leafy vegetables accumulate this element resulting in enrichment along the food chain. Silicon has beneficial effects in enhancing plants’ tolerance to biotic and abiotic stresses including heavy metals such as Pb. The study was carried out under greenhouse and field conditions aiming at determining the effects of silicon on transfer, mobility, and uptake of lead by leafy vegetables (spinach, kale, and amaranths). The greenhouse experiment was carried out as a split-plot arranged in Completely Randomized Design (CRD). The vegetable species were allocated to the main plots whereas the treatments (Pb, Pb+Si, Si, and Control) were assigned to the subplots. The field experiment was sited in polluted soils, and treatment included control and Si, applied to spinach, kale, and amaranths. Data was collected on Pb concentrations in roots, stems, and leaves, transfer factor, mobility index, and uptake of lead by leafy vegetables. Lead concentration was highest in roots, intermediate in stems, and least in leaves. Silicon application reduced concentration, transfer factor, mobility, and uptake of lead by 20, 40, 15, and 24%, respectively. The lead transfer factor and translocation index was less than one. Pearson correlation coefficient indicated a strong positive correlation between lead concentrations in soils and plant tissues of leafy vegetables. Application of silicon on polluted soils reduced transfer and mobility of lead in edible tissues of leafy vegetables. The study recommends silicon application to reduce the concentration of lead on vegetable tissues, however, it recommends against vegetable production for human consumption on polluted soils.