Figure 4.

Proposed rhizofiltration system. This technique is mainly used in metal phytoremediation. From a physiological perspective, root exudates and microorganisms (1) enhance bioavailability, followed by (2) the precipitation of metals. (3) Pollutant uptake is mediated and driven by both apoplastic and symplastic pathways. If symplastic pathways fail to translocate the pollutant into leaves and steam, chelation and sequestration takes place mainly in the roots of the plant. (4) Metals are chelated by metal binding ligands, phytochelatins and metalloteines, and finally pollutants are either sequestered into the cell vacuoles and the apoplast or bound to the cell wall [114,115,116,117].