Metal hyperaccumulators plants

However, some plants can accumulate more than 0.1% of Pb, Co, Cr, and more than 1% of Mn, Ni and Zn in the shoots. These accumulator plants are called hyperaccumulators. To date, there are approximately 400 known metal hyperaccumulator plants in the world (Baker and Walker, 1989). Thlaspi caerulescens, Alyssum murale, A. lesbiacum, A. tenium are Zn and Cd hyperaccumulators. Brassica juncea, a high-biomass plant, can accumulate Pb, Cr(III), Cd, Cu, Ni, Zn, Sr, B and Se. Thlaspi caerulescens accumulates Ni. Hybrid poplar trees are reported to phytoremediate Cd and As contaminated soils. A Chinese brake fem, Pteris vittata, is an As hyperaccumulator (Ma et al., 2001). 

Baker AIM, McGrath SP, Reeves RD, Smith JAC (2000) Metal hyperaccumulator plants a review of the ecology and physiology of a biological resource for phytoremediation of metal polluted soils. In Terry N, Banuelos GS (eds) Phytoremediation of contaminated soil and water. CRC Press, Boca Raton, pp 85-107... 

Soil. The first reported field trial of the use of hyperaccumulating plants to remove metals from a soil contaminated by sludge appHcations has been reported (103). The results were positive, but the rates of metal uptake suggest a time scale of decades for complete cleanup. Trials with higher biomass plants, such as B.juncea, are underway at several chromium and lead contaminated sites (88), but data are not yet available. 

Nickel is localized predominantly in the epidermal and subepidermal of the leaves. However, in leaves of some hyperaccumulator plants such as T. caerulescens and T. goesingense, Ni and Zn are found mainly in vacuoles (Salt and Kramer, 2000). Trace elements also are inactivated in the vacuoles as high-affinity low-molecular-weight metal chelators (such as Cd-phytochelatin complex), providing plants with trace element tolerance. Some Ni in leaves is found to be associated with cell wall pectates as well. 

Salt D.E., Kramer U. Mechanisms of metal hyperaccumulation in plants. In Phytoremediation of Toxic Metals Using Plants to Clean Up the Environment, I. Raskin, B.D. Ensley, eds. New York, NY John Wiley Sons, Inc., 2000. 

Chaney R. L., Angle J. S., Wang A. S., McIntosh M.S., Broadhurst L., and Reeves R. D., 2005, Phytoextraction of soil Cd, Ni and Zn using hyperaccumulator plants to alleviate risks of metal contaminated soils requiring remediation. International Workshop Current developments in remediation of contaminated lands p. 39, 27-29 October 2005. Pulawy, Poland. 

Assun9ao, A. G. L., Da Costa Martins, P., De Folter, S., Vooijs, R., Schat, H., and Aarts, M. G. M., 2001, Elevated expression of metal transporter genes in three accessions of the metal hyperaccumulator Thlaspi caerulescens. Plant Cell Environ. 24 217-226. 

Weber, M., Harada, E., Vess, C., v. Roepenack-Lahaye, E., and Clemens, S., 2004, Comparative microarray analysis of Arabidopsis thaliana and Arabidopsis halleri roots identifies nicotianamine synthase, a ZIP transporter and other genes as potential metal hyperaccumulation factors. Plant J. 37 269-281. 

In June of 1999, Edenspace Systems Corporation acquired Phytotech, Inc., a company specializing in phytoremediation technologies. Phytotech has developed several proprietary techniques for the phytoremediation of sites contaminated with heavy metals and radionuclides. Phytoremediation is an emerging bioremediation technology that uses plants to remediate contaminated media. Hyperaccumulation is a specific type of phytoremediation that can be used at sites contaminated by radionuclides and heavy metals. Hyperaccumulation may be defined as the ability... 

The search for the exact sites of ion and compound deposition in plants and the nature of the chemical species involved has been carried out with a number of aims The elucidation of various mechanisms of phytochemical importance mineral uptake and utilisation toxicity and tolerance exhibited by many individual species and the study of plants that accumulate or hyperaccumulate metals. The literature for a number of individual elements to the late 1970s has been reviewed (Farago, 1981) and the phytochemistry of metal hyperaccumulators has been reviewed by Baker and Brooks (1989). 

Hammer, D., Keller, C., McLaughlin, M. J., and Hamon, R. E. (2006). Fixation of metals in soil constituents and potential remobihzation by hyperaccumulating and non-hyperaccumulating plants Results from an isotopic dilution study. Environ. Pollut. 143, 407-415. 

Schwartz, C., Morel, J. L., Saumier, S., Whiting, S. N., and Baker, A. J. M. (1999). Root architecture of the Zn-hyperaccumulator plant Thlaspi caerulescens as affected by metal origin, content and localisation in soil. Plant Soil 208, 103-115. 

Y He, Z., and Stoffells, P.J., Molecular mechanisms of heavy metal hyperaccumulation and phytoremediation, J. Trace Elem. Med. Biol. 18, 339-353, 2005 Mackenzie, S.A., Plant organellar protein targeting a traffic plan still under construction. Trends Cell Biol. 15, 548-554, 2005 Thompson, M.V., Phloem the long and the short of it. Trends Plant Sci. 11, 26-32, 2006 Takahashi, H., Yoshimoto, N., and Saito, K., Anionic nutrient transport in plants the molecular basis of the sulfate transporter gene family. Genet. Eng. 27, 67-80, 2006. 

Studies have found many natural plant hyperaccumulators tend to have a higher density of metal transporters at the root-cell plasma membrane (Pence et al., 2000). The higher density of metal transporters allows these plants to readily take up metal cations from the soil solution. Once metals are accumulated, hyperaccumulating plant species usually exhibit a rapid translocation of accumulated metals from roots to shoots (Kramer, 2000). Translocated metals are then stored in vacuoles of the epidermal or mesophyllic cells of the stem to decrease toxicity to the plant (Mathys, 1977). 

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