Biotechnological Use of Cadmium Hyperaccumulators

In all cases of anthropogenic contamination of soils with heavy metals, the highest heavy metal concentrations are found rather close to the surface, although not directly in the uppermost few mm to cm as these are leached by rain like in natural heavy metal sites [130,131]. For this reason, a decontamination of such areas is, in principle. 

Many natural hyperaccumulators, i.e., plants that actively accumulate several percent of heavy metals in the dry mass of their above-ground parts, have a good potential to be used for phytoremediation, i.e., to extract and remove heavy metals from anthropogenically contaminated soils, which was first proposed by Chaney [132]. Some of them even allow for commercially profitable phytomining, i.e., the extraction of metals from naturally heavy metal rich soils (that are not directly usable as metal ores) with subsequent burning of the plants, the ash of which can be used as a metal ore (first proposed by Baker, Brooks, and Reeves [133]). These applications of metal phytoextraction have been a subject to extensive research (for reviews see [3,31,132,134-141]. 

In contrast, field trials have shown that the biomass of namral hyperaccumulators can be dramatically increased by addition of fertilizer, namral selection, and classical breeding to reach levels that are economically attractive (reviewed by Chaney et al. [139]). As a source for selecting species that are suitable for a specific phytoextraction tasks, conservation of metallophyte biodiversity is of prime importance as outlined by Whiting et al. [173]. 

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