Metal storage in reeds from an acid mine drainage contaminated field

Phragmites australis has been used to treat acid mine drainage (AMD)-contaminated soil. However, the mechanism about metal translocation in reeds was not widely reported. This study investigated metal (Fe, Al, and Mn) storage location in reeds grown in five different sampling sites of an AMD field. As expected, the more metals in soil, the more metals entered the belowground organs of plants. Reeds grown in soils with the highest levels of metals accumulated 0.16 ± 0.04 mg/g Mn, 16.29 ± 4.15 mg/g Fe, and 1.31 ± 0.22 mg/g Al in roots. Most of the iron was sequestered in the roots, while Al was transferred to the shoots. Histological staining found that most of the iron was sequestered in the exodermis, while Al extended the endodermis of roots. Al even entered the stele of roots grown in soil with higher Al levels. The epidermis, cortex, and central cylinder of rhizomes were the main tissues for Fe and Al storage. The more metals in rhizomes, the stronger intensity of the staining was observed around the vascular systems of rhizomes. No structural difference was observed among reeds collected from different sites. Further studies may be needed to enhance the transfer of metals in reeds and increase the phytoremediation efficiency.