Response of a New Zealand tree fern

Lead (Pb) pollution is a serious environmental problem. Phytoremediation is emerging as a promising technology for removal of Pb and other heavy metals from soils and waterways. In this study, the phytoremediation potential of a popular landscape plant, in New Zealand, Cyathea medullaris (the black tree fern), was investigated. Pb uptake by the gametophytes and different parts (roots, shoots and leaves) of 3-month-old black tree fern plants in hydroponic experiments were studied using flame atomic absorption spectrometry. Morphological and ultrastructural changes in the Pb-treated materials were also investigated. Generally, the levels of Pb in the various black tree fern tissues increased with the external Pb concentration and exposure time. Transmission electron microscopy observation showed that the cell wall was the major subcellular site for Pb accumulation. Evidence obtained here suggests that the black tree fern gametophytes and the sporophyte can accumulate levels of Pb exceeding 1% of their dry weights. This resembles the capacity of a hyperaccumulating plant