Schematic representation of root tissues with transport proteins involved in Cd transport. The cell walls are not shown. The apoplastic pathway travels through cell walls and apoplastic fluid and reaching the xylem in the root parts, where apoplastic barriers (Casparian band, suberin lamellae) are absent. Cadmium is represented as free hydrated ions (Cd²⁺) or as complexes with organic ligands (Cd–L). L_C: Ligands of Cd in cytosol; L_V: ligands in vacuole; L_X: ligands in xylem.