Effects of silicon on the transport, subcellular distribution, and chemical forms of lead in Salix viminalis L.

Lead (Pb) is a harmful heavy metal that threatens ecosystems and plant growth. Silicon (Si) plays a crucial role in plant responses to heavy metal stress. In this study, the effects of Si on Pb2+ content and transport, subcellular distribution, and chemical forms in <i>Salix viminalis</i> L. under Pb stress were analysed, aiming to elucidate the detoxification mechanism of Si in <i>S. viminalis</i> under such conditions. Results showed that Si reduced Pb²⁺ in aboveground parts and increased it in roots, lowering its movement to leaves and stems. Analysis of the subcellular distribution of Pb²⁺ revealed that Si application promoted the transfer of Pb²⁺ to vacuole-dominated soluble components (F4) and cell wall components (F1), which increased the binding capacity of the cell wall and the vacuolar storage compartmentalisation for Pb²⁺. Changes in the chemical forms of Pb²⁺ indicated that Si significantly decreased the proportion of more mobile, ethanol-extractable Pb²⁺ (FE) and deionised water-extractable Pb²⁺ (FW) while increasing the proportion of less mobile Pb²⁺ forms, such as NaCl-extractable (FNaCl), HCl-extractable (FHCl), and acetic acid-extractable (FHAc) Pb²⁺, thereby reducing its mobility. This study provides empirical support for the application of Si in the phytoremediation of heavy metal-contaminated soils.