Hyperaccumulator plants mechanisms

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. 

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). 

The mechanism of As hyperaccumulation is of great interest because, to most plants, inorganic arsenite species are more toxic. As hyperaccumulation is a trait inherent to... 

Wang, J., Zhao, F.J., Meharg, A.A., Raab, A., Feldmann, J., and McGrath, S.P. 2002. Mechanisms of arsenic hyperaccumulation in Pteris vittata. Uptake kinetics, interactions with phosphate, and arsenic speciation. Plant Physiology, 130 1552-61. 

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. 

Many microorganisms and plants are capable of transforming toxic chemical species into less toxic forms (e.g., Lytle et al. 1996, 1998 Hunter et al. 1997). Some plants are particularly useful for remediation of contaminants in soils and natural waters because they hyperaccumulate specific toxins (e.g., Van der Lelie et al. 2001 Fuhrmann et al. 2002). In most cases, however, the molecular-scale mechanisms of these transformations or of hyperaccumulation are not known. This is a fertile research field for geochemists and mineralogists that will require multidisciplinary studies and will benefit from SR-based microspectroscopy methods. 

It could be concluded that, elements that can be hyperaccumulated include As (>0.1 %), Cd (>0.01 %), Co (>0.1 %), Cu (>0.1 %), Pb (>0.1 %), Mn (>1 %), Ni (>0.1 %), Se (>0.1 %) and Zn (>1 %). It could be also mentioned that, the element levels accumulated in these plants would be lethal to other organisms, yet cause no toxicity in hyperaccnmulators. The Se-tolerance mechanism of hyperaccumulators can be followed by nsing microfocused X-ray fluorescence (pXRF) mapping and micro-X-ray absorption near edge structure (pXANES) spectroscopy, which revealed a stark contrast in spatial distribution and chemical speciation of Se between hyperaccnmnlators and nonaccumulators. 

The mechanisms by which plants hyperaccumulate heavy metals in their shoots and prevent phytotoxicity of these metals have been the subject of many studies. Nonetheless, many of these mechanisms are still under debate. 

While the following sections deal with mechanisms of hyperaccumulation on the cellular and molecular level, it should also be noted that hyperaccumulation is modified by interactions between plants and arbuscular mycorrhizal fungi [61]. In this study, the colonisation of the plant roots with these fungi reduced Cd uptake and thus increased metal tolerance of the plants, but in studies on other plants... 

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