Metal hyperaccumulation and bioremediation

Abstract

The phytoremediation is an environment friendly, green technology that is cost effective and energetically inexpensive. Metal hyperaccumulator plants are used to remove metal from terrestrial as well as aquatic ecosystems. The technique makes use of the intrinsic capacity of plants to accumulate metal and transport them to shoots, ability to form phytochelatins in roots and sequester the metal ions. Harbouring the genes that are considered as signatures for the tolerance and hyperaccumulation from identified hyperaccumulator plant species into the transgenic plants provide a platform to develop the technology with the help of genetic engineering. This would result in transgenics that may have large biomass and fast growth a quality essential for removal of metal from soil quickly and in large quantities. Despite so much of a potential, the progress in the field of developing transgenic phytoremediator plant species is rather slow. This can be attributed to the lack of our understanding of complex interactions in the soil and indigenous mechanisms in the plants that allow metal translocation, accumulation and removal from a site. The review focuses on the work carried out in the field of metal phytoremediation from contaminated soil. The paper concludes with an assessment of the current status of technology development and its future prospects with emphasis on a combinatorial approach.

Phytoremediation Potential of Aquatic Macrophyte, Azolla

“…Hyperaccumualtion of heavy metal involves several steps, such as transport of heavy metal across plasma membrane, translocation of heavy metal, detoxification, and sequestration at cellular and whole plant level (Shah and Nongkynrih 2007;Rascio and Navari-Izzo 2011). In recent years, the understanding of entry of both essential and nonessential metal ions in plant cells at the molecular level, has greatly advanced.…”

“…Different chelators contribute to metal detoxification by buffering cytosolic metal concentrations, whereas chaperone specifically delivers metal ions to organelles and metal requiring proteins. In plants, the principal classes of metal chelators include phytochelatins, metallothioneins, organic acids, and amino acids (Shah and Nongkynrih 2007).…”

Zinc and cadmium accumulation by Lupinus uncinatus Schldl. grown in nutrient solution

“…Heavy-metal-tolerant plants belonging to the genera Alyssum, Thalspi, or Silene have been identified (Brooks 1998;Dede et al 2012;Shah and Nongrynrih 2007), and their use for phytoextraction purpose has been recommended (Schwartz et al 2003;Zhao et al 2003). Some of the metaltolerant plants are also hyperaccumulators, as a hyperaccumulator has been defined as a plant that can accumulate cadmium[100 mg/kg or zinc[10,000 mg/kg in their shoot dry matter, and the metal concentrations in shoots are invariably greater than that in roots, showing a special ability of the plant to absorb and transport metals and store them in their aboveground part (Baker et al 1994).…”

Significant Role of Ornamental Plants as Air Purifiers – A Review

“…Trees are ideal in the remediation of heavy metals as they can withstand and accumulate higher concentration of pollutants owing to their large biomass and size, can reach a huge area and great depths for their extensive rootings and can stabilize an area (Shah and Nongkynrih, 2007) Fast-growing trees (such as poplar, pine, and eucalyptus) and the hardwood trees, mahogany and rosewood, as well as poplar and eucalyptus, can be used for remediation of contaminated air. The total amount of air pollution removed by urban trees annually within the United States is estimated to be 711,000 metric tons (Nowak et al, 2006) Concentrations of five metals (cadmium, chromium, copper, nickel and lead) were determined in tree leaves collected from 13 areas of the Attica basin and Athens city, Greece.…”