Abstract: Environmental pollution is one of the major problem for human health. Toxic heavy metals are normally present as soil constituents or can also be spread out in the environment by human activity and agricultural techniques. Soil contamination by heavy metals as cadmium, highlights two main aspects: on one side they interfere with plants life cycle and therefore reduce crop yields, on the other hand, once adsorbed and accumulated into the plant tissues, they enter the food chain poisoning animals and humans. Considering this point of view, understanding the mechanism by which plants handle heavy metal exposure, in particular cadmium stress, is a primary goal of plant-biotechnology research or plant breeders whose aim is to create plants able to recover high amounts of heavy metals, which can be used for phytoremediation, or identify crop varieties that do not accumulate toxic metal in grains or fruits. In this review we will focus on the main symptoms of cadmium toxicity both on root apparatus and shoots. We will elucidate the mechanisms that plants activate to prevent absorption or to detoxify toxic metal ions, such as synthesis of phytochelatins, metallothioneins and enzymes involved in stress response. Finally we will consider new plant-biotechnology applications that can be applied for phytoremediation.

Key words: cadmium, heavy metals, metallothioneins, phytochelatins, phytoremediation, transporters