The major challenge facing society in the twenty-first century is to feed and provide for increasing numbers of people while protecting human health and the environment. To accomplish this we must combine traditional technologies with modern technologies. Contamination of soil and water by industrial effluents and sewage waste is one of the major problems faced by the modern world. The intensive use of potentially toxic compounds by industry and past failures to properly dispose of hazardous material particularly toxic metals now necessitate new methods for the remediation of polluted soil and water. Research efforts are currently being directed at the development of being less invasive, more economical plant-based phytoremediation technology in removing toxic pollutants particularly toxic metals. Plants have a remarkable ability to extract and concentrate elements and compounds from air, water, and soil. They spend most of their lives as solar-driven pumping stations and chemical factories. Recently, attempts have been made to harness this ability for purposes of environmental remediation. The term phytoremediation has been introduced to describe this process. Phytoremediation is the use of plants to remove pollutants from the environment or to render them harmless. This is being developed as a technology for remediating volatile and nonvolatile organic and toxic metal pollution. However, removal of toxic metals from soils is an area in which phytoremediation may have a particular impact because of the lack of alternative technologies that are affordable and effective. Plants that hyperaccumumulate toxic metals are rare. Such hyperaccumulators are taxonomically widespread throughout the plant kingdom. More than 350 species of plant are known to accumulate metal such as nickel, zinc, copper, cadmium, selenium or manganese in high levels. For example, naturally occurring hyperaccumulating plants like Thlaspi caerulescens, Serbetia accuminata, Alyssum and Astragolum species which acquire in their tissues high levels of metals such as cadmium, zinc, nickel, have been shown to sequester more than 1% of their dry mass of heavy metals from contaminated soil. Over the past 20 years, many crop and related weed species have been screened for metal uptake, translocation and tolerance. Much effort has been focussed on the Brassica family to which many hyperaccumulators species belong. However, the potential for application of hyperaccumulators in phytoremediation is limited by several factors such as slow growing, generate insufficient biomass for practical large-scale application, and demonstrate affinity for only one or two toxic elements.
A fundamental understanding of the biochemical processes involved in plant metal uptake, translocation and hyperaccumulation in normal and metals hyperaccumulators, regulatory control of these activities, and the use of tissue-specific promoters offers great promise that use of molecular biology tools can give scientist the ability to develop effective and economic phytoremediation transgenic plants for toxic metals. So, a long term effort should be directed towards developing a “molecular tool box” composed of genes valuable for phytoremediation.