In soil, cadmium (Cd) is mainly adsorbed onto organic matter and iron hydroxides. Due to the difference in transmembrane electrochemical potential, the hydrated ions (Cd2+) present in the soil solution at the nanomolar level penetrate root cells. They hijack nutrient transporters such as those for iron, manganese, and zinc. Cadmium is mostly sequestered in the vacuoles of root cells, but some diffuses towards the vascular bundles, where it is released into the raw sap. It thereby reaches the aerial parts with the sap flow driven by transpiration. Transport proteins allow Cd to be released into the cells of stems and leaves, where is it stored and detoxified in the vacuoles and in the cell walls. A significant part of the Cd absorbed can be translocated via the phloem, depending on the plant species. It is through phloem flow that Cd reaches the seeds, either directly from the roots or through remobilisation from the stems and leaves. The Cd content in crops depends primarily on the soil Cd content and availability, and secondarily on the crop genotype. In France, while much has been done to reduce Cd availability in soils, genetic selection is a potential solution to further reduce the metal in harvests.
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