Ecophysiological effects of high concentrations of iron and other heavy metals on Eriophorum angustifolium Honck. and Phragmites australis (Cav.) Trin ex steudel
Little is known of the effect of high concentrations of heavy metals on the growth of wetland plants, although it is has long been suggested that adaptation to waterlogged anaerobic environments involves the capacity to exclude dissolved iron. This work investigates the chemical dynamics of selected metal toxins, in particular Fe in relation to concentration in the substrate and uptake b y Eriophorum augustifolium, and Phragmites australis taken from mine populations (Parys Mountain, Anglesey and Crymlyn Bog , Swansea) and a non-mine population (Skipwith Common, Yorks) and to provide information on the resistance of these two species to high concentrations of Fe and other heavy metals. Both field and laboratory work have been used to focus on the above areas. The first part of the study is based on the analysis of plants and soil samples collected from the field and relates heavy metal concentration in plant tissue to concentrations in soil/sediments. The second part of the study is based on laboratory work to determine individual factors influencing heavy metal uptake and resistance in the study species. Fe, Mn, Cu, Zn and Pb concentrations in plant tissues reflected those in the soil. Seasonal fluctuations in metal concentration in plant tissues were observed but the bulk differences were related to soil heterogeneity between sites. In culture solutions, Fe uptake in both species increased with increasing Fe supply. E. augustifolium from the Parys site was less sensitive to hi g h Fe concentrations relative to plants from the Skipwith site. Fe-uptake by E angustfolium, was strongly influenced by pH. Fe--uptake by plants was unaffected by the presence of Fe-plaques on roots. A relationship between Fe and P is highlighted enhancing P availability to plants of E. augustifolium in th presence of 100 mg /l Fe by treating half the roots with Fe and the remaining half with 0.1-strength Rorison solution with 1 mg/l Fe, stimulated root oxidation of Fe and the accumulation of Fe-plaque, reducing translocation of Fe to shoots. P].ants of the same species with Fe-plaque an the roots accumulated more P than plants without plaque, the bulk of this P was immobile. E. angustifolium from the Parys Mountain site was found to be more tolerant to Cu but more sensitive to Mn, the reverse was true for p).ants from the Skipwith site. The imp1ications of this work in relation to plant growth and resistance to heavy metal—enriched environments are discussed. It is suggested that both species may be constitutionally tolerant to Fe and Mn. Plants from the Parus site may be more resistant to high concentrations of Cu, Zn and Pb.