Submitted to: Proceedings of the Phytoremediation Conference
Publication Type: Abstract Only
Publication Acceptance Date: 9/4/2005
Publication Date: 9/10/2005
Citation: Baligar, V.C., Lu, L.L., Yang, X.E. 2005. Mechanisms of nickel uptake and hyperaccumulaton by the plants and implication to phytoremediation. Proceedings of the Phytoremediation Conference.
Technical Abstract: More than 300 plant species are known to be Ni hyperaccumulators, and these are capable of accumulating a very high concentrations of Ni without any adverse effects. Progress is being made to understand the physiological, biochemical, molecular and genetic basis of Ni tolerance and hyperaccumulation in these plant species. Ni hyperaccumulators have devised improved root uptake, transport to shoot and internal detoxification mechanisms to tolerate high levels of Ni. These plants have developed effective uptake mechanisms to absorb elevated nickel from soil by various ways, including improved metal solubility in soil by reducing pH, increasing root exudation of organic solutes, and effective communications with rhizosphere bacteria. Plants also produce ACC deaminase enzyme to reduce amount of ethylene which protects plants from Ni toxicity. Hyperaccumulators are capable of translocating large amount of Ni from roots to shoots by metal transporter like tgMTP which transport Ni form xylem apoplast to shoot symplast. Besides binding Ni to cellular inactive sites, a high proportion of Ni is complexed and stored in vacuoles with organic acids, including citric, malic and malonic acids. Nickel is also chelated with ligands such as histidine and glutamine in xylem for transport to shoots. Recent studies with hyperaccumulators has suggested that glutathione plays an important role in detoxification of extravacuolar Ni by protecting cells against oxygen radicals to increase nickel resistance. The extraordinary ability of these plants to hyperaccumulate Ni make them an ideal source of genetic materials in development of phytoremediaion technology for metal polluted soils and water system.