Metal stress in plants: its detoxification in natural environment

In natural environment, plants consist of both metabolic and tolerant mechanisms in toxic non-essential metals like Arsenic, Cadmium, Lead and Mercury. Natural activities composed of mining and smelting operations, including some haphazard practices in agriculture, have extensively contaminated some areas around the world—as for instances, in India, Japan, Indonesia and China by Cadmium, Copper and Arsenic and Copper and Lead in Greece. In fact, South-East Asia is suffering from the contamination of the groundwater Arsenic, as in the same way the existence of Copper, Lead, Nickel, Zinc and Cadmium is nothing new in some parts of Australia. Indeed, heavy metal contamination has become a worldwide problem. The uptake as well as accumulation of the aforesaid metals by plants is the main factor responsible for threatening the health of both man and animal into their food by toxic metals. The production of phytochelatins, a metal-binding thiol peptide and metallothionin, to react against the heavy metal stress may have provided for an appropriate metal tolerance in plants but needs a comprehensive study on it; for a better understanding on the different metal transports, their accumulations as well as over expressions in plants would definitely pave the better ways to develop metal tolerant plants or transgenics. Keeping the rising concerns over heavy metal stress affecting agriculture produce and plants in view in water; this review aims at throwing light as a tip on the iceberg about the physiological and biochemical mechanisms of metal accumulations, their responses and detoxification to the toxicity as well as to the metal stress tolerant plants.