Effect of soil-applied lead on mineral contents and biomass in Acer cappadocicum, Fraxinus excelsior and Platycladus orientalis seedlings

Phytoremediation is an effective and affordable approach to extract or remove lead from contaminated soil. An understanding of the physiological responses of different species subjected to heavy metal contamination is necessary before considering their use for environmental clean-up. The objective of this study was to assess the effect of lead (Pb) on growth and nutrient uptake in three forest species native to Iran: Cappadocian maple (Acer cappadocicum), European ash (Fraxinus excelsior) and Oriental aborvitae (Platycladus orientalis). The capability of lead uptake in different organs was studied in one-year-old potted seedlings grown in contaminated soils with Pb concentration ranging from 100 to 500 mg kg(-1) for six months in a nursery. Several phytoextraction parameters such as translocation factor (TF), tolerance index (TI) and bioconcentration factor (BCF) were assessed to investigate the phytoremediation potential of these species. Increasing Pb application in the soil caused a gradual decrease in dry weight of leaf and shoot of all species, while the dry weight of root remains unaffected. However, such inhibition was less marked in the conifer (P. orientalis) compared to the two broad-leaf species. Phosphorus uptake of all species slightly declined in contaminated soils. Contrastingly, Pb application did not hinder nitrogen and potassium uptake in seedlings. Atomic absorption thermo electron analysis of Pb-treated plants showed an increasing Pb accumulation in all plant compartments, although the result was more evident in the tissues of P. orientalis. This species also showed the highest values for TF, TI and BCF, indicating this conifer species as a potential candidate for phytoremediation of lead-polluted soils in Iran.