Tolerance of Heavy Metals in Vascular Plants: Arsenic Hyperaccumulation by Chinese Brake Fern (Pteris Vittata L.)

Abstract

Arsenic, a carcinogenic metalloid, occurs naturally in the earth’s crust. However, a host of anthropogenic activities during the 20^th century, contributed to dramatic increases in arsenic levels in the biosphere. Recently, one particular pteridophyte, a fern, commonly known as Chinese Brake fern (Pteris vittata L.), has generated a global interest due to the discovery of its unique property of hyperaccumulating arsenic in the fronds from both contaminated and uncontaminated sites (Ma et al., 2001a). The emergence of this arsenic-loving fern offers a great promise to phytoremediation, a plant-driven environmentally benign clean up process wherein the roots take up colossal amounts of a toxic metal from soils and rapidly sequester into their above-ground portions. Plants capable of accomplishing such features use termed as hyperaccumulators. Chinese Brake fern qualifies as an arsenic hyperaccumulator and thus has potential application in phytoremediation of arsenic contaminated sites. In order to model a successful phytoremediation strategy for arsenic contaminated sites, one must first gain a comprehensive knowledge of the sequential biological processes involved in arsenic uptake, translocation, and hyperaccumulation in the fronds. In this chapter, we present a conceptual framework for the phytoremediation of arsenic-contaminated sites by describing plant morphology of the Chinese Brake fern and its geographical distribution, ecophysiology and mechanism of arsenic hyperaccumulation in the light of accumulated knowledge on heavy metal tolerance in higher plants.