Phytoextraction

Phytoextraction is a subprocess of phytoremediation in which plants remove dangerous elements or compounds from soil or water, most usually heavy metals, metals that have a high density and may be toxic to organisms even at relatively low concentrations. The heavy metals that plants extract are toxic to the plants as well, and the plants used for phytoextraction are known hyperaccumulators that sequester extremely large amounts of heavy metals in their tissues. Phytoextraction can also be performed by plants that uptake lower levels of pollutants, but due to their high growth rate and biomass production, may remove a considerable amount of contaminants from the soil..

Heavy metals can be a major problem for any biological organism as they may be reactive with a number of chemicals essential to biological processes.

They can also break apart other molecules into even more reactive species (such as:Reactive Oxygen Species), which also disrupt biological processes. These reactions deplete the concentration of important molecules and also produce dangerously reactive molecules such as the radicals O^. and OH^..

Non-hyperaccumulators also absorb some concentration of heavy metals, as many heavy metals are chemically similar to other metals that are essential to the plants life.

For a plant to extract a heavy metal from water or soil, five things need to happen. 1.The metal must dissolve in something the plant roots can absorb. 2.The plant roots must absorb the heavy metal. 3.The plant must chelate the metal to both protect itself and make the metal more mobile(this can also happen before the metal is absorbed)j.

4.The plant moves the chelated metal to a place to safely store it 5.Finally, the plant must adapt to any damages the metals cause during transportation and storage

In their normal states, metals cannot be taken into any organism. They must be dissolved as an ion in solution to be mobile in an organism. Once the metal is mobile, it can either be directly transported over the root cell wall by a specific metal transporter or carried over by a specific agent. The plant roots mediate this process by secreting things that will capture the metal in the rhizosphere and then transport the metal over the cell wall. Some examples are: phytosiderophores, organic acids, or carboxylates If the metal is chelated at this point, then the plant does not need to chelate it later and the chelater serves as a case to conceal the metal from the rest of the plant. This is a way that a hyper-accumulator can protect itself from the toxic effects of poisonous metals.

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Wikipedia