As hyperaccumulators

However, some plants can accumulate more than 0.1% of Pb, Co, Cr, and more than 1% of Mn, Ni and Zn in the shoots. These accumulator plants are called hyperaccumulators. To date, there are approximately 400 known metal hyperaccumulator plants in the world (Baker and Walker, 1989). Thlaspi caerulescens, Alyssum murale, A. lesbiacum, A. tenium are Zn and Cd hyperaccumulators. Brassica juncea, a high-biomass plant, can accumulate Pb, Cr(III), Cd, Cu, Ni, Zn, Sr, B and Se. Thlaspi caerulescens accumulates Ni. Hybrid poplar trees are reported to phytoremediate Cd and As contaminated soils. A Chinese brake fem, Pteris vittata, is an As hyperaccumulator (Ma et al., 2001). 

The term indicator plant has been used somewhat differently. Qualitatively, indicator plants are diagnostic of certain environmental conditions, and these can fall into any of Baker s three categories. To avoid confusion, it has been suggested (Farago and Mehra, 1992) that the term concentration indicator should be used to describe plants where the plant soil concentration ratios are near 1. These three types are represented in Fig. 8-2. Some plants endemic to metalliferous soils acccumulate very high concentrations in their aerial parts and these are known as hyperaccumulators (Baker and Brooks, 1989 Chapters 3 and 4). Such plants are able to accumulate metals not only from soils with high metal concentrations, but also from soils with concentrations only marginally above normal. 

An alternative remediation strategy is to exploit higher plants that are capable of taking up exceptional amounts of metals and metalloids from the soil solution and confine it in the aboveground plant tissues. These plants have been termed as hyperaccumulators and their unique property is exploited in the in situ remediation technology of phytoremediation, which is ecologically safe, cost effective, and easy... 

As we mentioned earlier, certain plant species are capable of taking up very high amounts of metals from the soil and water. Although As hyperaccumulators bioconcentrate As over 2000 mg kg in plant tissues, the biomass production rates of most of hyperaccumulator species are low. Therefore, a lack of rapid growth, large biomass... 

The mechanism of As hyperaccumulation is of great interest because, to most plants, inorganic arsenite species are more toxic. As hyperaccumulation is a trait inherent to... 

Certain species of plants have been found to accumulate very high concentrations of certain trace elements and these are referred as hyperaccumulator species. Plants can also intercept significant amounts of some elements through foliar absorption. Foliar absorption of solutes depends on the plant species, its nutritional status, the thickness of its cuticle, the age of the leaf, the presence of stomata guard cells, the humidity at the leaf surface, and the nature of the solutes. 

---