Responses of Populus deltoides x Populus nigra (Populus x euramericana) clone I-214 to high zinc concentrations

We hypothesized that poplar can be useful for the extraction of zinc (Zn) from contaminated soils and water. However, the physiological response and the base of tolerance of poplar plants to this heavy metal are little known. Plants of Populus deltoides x P . nigra (P. x euramericana ) I-214 clone were grown in glasshouse and treated with three different Zn concentrations (1, 100 and 1000 mum). Growth analysis, Zn concentration in leaves, stem and roots, and photosynthetic parameters were measured at different times of exposure during the annual growth cycle. Significant reductions in foliage and total dry mass, and impairment of gas exchange properties occurred at applications of 100 mum and 1000 mum Zn. Modifications of leaf area, chlorophyll b concentration, diameter at the stem base, and Zn concentrations of old leaves, stem and roots were also shown after Zn treatment. We concluded that poplar plants have the potential to be used for plantations in Zn-contaminated soils, in the range of tested Zn concentrations.