Evaluation of the ability of Nerium oleander L. to remediate Pb-contaminated soils

In the present paper we studied the accumulation of Pb in the species Nerium oleander, found growing in a mining area (Riotinto, SW Spain). Soil samples were taken around plants to characterize Pb contamination, and plant samples were collected in different sites in order to determine Pb content in leaves, stems and roots. Additionally, a hydroponic experiment was performed to determine critical Pb concentrations for plant growth and investigate the Pb tolerance strategy. Plants were exposed to different Pb concentrations (0, 20, 40, 80, 100 μM) during 30 days. We measured growth rates, water content (%), photosynthetic pigments (chlorophyll a, b, and carotenoids), and biochemical parameters (MAD, CAT, POD). The median total Pb concentration in soils where N. oleander grows was approximately 270 mg/kg, but the plant accumulated only 2 mg/kg in leaves, 13 mg/kg in the inner part of the roots and 26 mg/kg in the root bark (median values). Bioaccumulation (leaf/soil ratio) and translocation factor (leaf/root ratio) were lower than 1, indicating that the species did not translocate Pb to the aerial parts, which may be useful with regard to phytostabilizing Pb traits together with the ornamental flowers. Lead treatment inhibited plant growth and increased malondialdehyde (MDA) content in leaves, and at the higher Pb concentration (100 μM), toxicity symptoms occurred.

► We studied the accumulation of Pb in Nerium oleander species growing in a mining area. ► We examine the soils around plants to study soil/plant relations. ► We find that the species accumulate Pb mainly in the roots. ► In a hydroponic experiment a treatment with 100 μM Pb induces toxic symptoms.