More recently, researchers have reported inordinately large concentrations (e.g. ppm to %-wt) of metals in some plants [12].To this end, Baker and Brooks [13] classified plants into three categories:(i) excluders; plants which do not take up metals, (ii)hyperaccumulators; those which take up abnormally large quantities of metal and (iii) indicators; those which take up metal in proportion to its quantity in the soil. Hyperaccumulators of many heavy metals have already been identified; approximately317 nickel, 24 copper and 26 cobalt hyperaccumulators to date [14],although none for the noble metals. Harris and Bali [15]previously evaluated the ability of Medicago sativa (MS) and Brassica juncea (BJ), two known metallophytes (metal loving plants),to reduce and hyperaccumulate Ag(0) from aqueous solutions of Ag(I). In this work the whole plant Ag concentration was up to 14 wt.%-dry basis and 12 wt.%-dry basis in MS and BJ respectively.
To the best of our knowledge however, there are no published accounts of the hyperaccumulation of Au in the literature.
Anderson [16] reported the induced accumulation of Au,up to 57mgAu kg−1 dry weight in the leaves of BJ using thiocyanate as a chelating agent. Rodriguez [17] and Parsons et al.[18] showed that MS cultivated on Au enriched media accumulated
56mgAu kg−1 shoot dry weight after 14 d exposure.
However, neither report meets the definition for hyperaccumulation.
More recently, researchers have reported inordinately large concentrations (e.g. ppm to %-wt) of metals in some plants [12].To this end, Baker and Brooks [13] classified plants into three categories:(i) excluders; plants which do not take up metals, (ii)hyperaccumulators; those which take up abnormally large quantities of metal and (iii) indicators; those which take up metal in proportion to its quantity in the soil. Hyperaccumulators of many heavy metals have already been identified; approximately317 nickel, 24 copper and 26 cobalt hyperaccumulators to date [14],although none for the noble metals. Harris and Bali [15]previously evaluated the ability of Medicago sativa (MS) and Brassica juncea (BJ), two known metallophytes (metal loving plants),to reduce and hyperaccumulate Ag(0) from aqueous solutions of Ag(I). In this work the whole plant Ag concentration was up to 14 wt.%-dry basis and 12 wt.%-dry basis in MS and BJ respectively.To the best of our knowledge however, there are no published accounts of the hyperaccumulation of Au in the literature.Anderson [16] reported the induced accumulation of Au,up to 57mgAu kg−1 dry weight in the leaves of BJ using thiocyanate as a chelating agent. Rodriguez [17] and Parsons et al.[18] showed that MS cultivated on Au enriched media accumulated56mgAu kg−1 shoot dry weight after 14 d exposure.However, neither report meets the definition for hyperaccumulation.
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