Baseline concentrations of copper and zinc in shoot tissues of a range of Salix species

Background concentrations of Cu and Zn in bark, leaves, twigs and wood of eight species of Salix (willow) growing on the same soil type were investigated. It was found that the concentrations of Cu and Zn varied between plant parts and between species. There was no consistent pattern of metal concentration. Copper concentrations decreased in the order twigs > leaves > wood > bark, and those of Zn in the order leaves > bark > twigs > wood. The eight species did not show a common uptake pattern for the two metals. S. × sericans and S. cinerea had high concentrations of both metals; S. purpurea had high concentrations of Zn but low concentrations of Cu, whilst S. fragilis and S. viminalis had low concentrations of both metals. Concentration factors for both elements in shoot tissues were consistent, despite the variations in associated metal concentrations. A general trend of exclusion of Cu and concentration of Zn was evident. More Cu than Zn was fixed in woody tissue.