Heavy Metals Accumulation Ability of Wild Grass Species from Industrial Areas of Kazakhstan

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The classical and recent literature on phytoremediation of soils contaminated by heavy metals is analyzed; information about plants hyperaccumulators of heavy metals for phytoremediation, types of phytoremediation, mechanisms of hypertolerance and hyperaccumulation, the role of phytosiderophores in phytoremediation, opportunities of the use of “energy” plants, and transgenic plants for phytoremediation are discussed. Several ways to improve plants for phytoremediation as metal-helating agents, agronomic practices, conventional breeding, and gene-engineering methods are discussed. Experimental data on the test of wild grass species Agropyron repens, Agrostis alba, Bromus inermis, Dactylis glomerata, Phleum pratense, and Setaria viridis growing around metallurgic plants of East Kazakhstan on metal-accumulating ability are presented. All species have accumulated Zn and Pb mainly in the roots. These species were tested in artificial contaminated soils and hydroponic conditions on tolerance to heavy metal in field and hydroponic conditions. A. repens and S. viridis were more tolerant to Pb and Zn according to data from the hydroponic experiments treated with extremely high concentrations of Pb and Zn, P. pratense was more sensitive. The shoot/root Pb ratio was 1 for all species, except for A. repens and A. alba. In pot experiments, these grass species accumulated trace metals mainly in the roots. The possibilities of using these grass species for phytostabilization are discussed.