Possible Molecular Mechanisms Involved in Nickel, Zinc and Selenium Hyperaccumulation in Plants

Abstract

Most hyperaccumulator species are able to accumulate between 1-5% of their biomass as metal. However, these plants are often small, slow growing, and do not produce a high biomass. Phytoextraction, a cost-effective, in situ, plant-based approach to soil remediation takes advantage of the remarkable ability of hyperaccumulating plants to concentrate metals from the soil and accumulate them in their harvestable, above-ground tissues (Salt et ai., 1998). However, to make use of the valuable genetic resources identified in metal hyperaccumulating species, it win be necessary to transfer this material to high biomass, rapidly growing crop plants (Salt et al., 1998). These plants would then be ideally suited to the phytoremediation process, having the ability to produce a large amount of metal-rich plant biomass for rapid harvest and soil cleanup. It is becoming clear that the hyperaccumu]ator plant's genetic material could also be very valuable in enhancing the nutritional value of human foodstuffs. Malnutrition remains one of the most serious problems facing mankind and1 although remarkable improvements in crop productivity have been made over the last twenty years, it is now clear that this has been made at the expense of the nutritional value of the foodstuff produced. Deficiencies in such micronutrients as iron, zinc~ selenium, iodine and vitamin A are often referred to as the 'hidden hunger'. Substantial efforts