Cadmium and copper uptake and distribution in Mediterranean tree seedlings

Copper and cadmium uptake and distribution in 2-week-old seedlings of stone pine (Pinus pinea L.), maritime pine (Pinus pinaster Ait.) and ash (Fraxinus angustifolia Vahl.) were investigated. Seedlings were grown in culture solution at increasing concentrations of CuSO4 (0.012-5 mu M) and CdSO4 (0.0-5 mu M). All species accumulated copper in a larger amount than cadmium, Translocation to the shoot was strongly restricted for both metals, though higher cadmium mobility within the plant could be evidenced. A strong relationship between root content and growth inhibition was detected in the roots in response to copper but not to cadmium treatments, Among species P. pinea seemed to be more tolerant to cadmium, whereas F: angustifolia was highly sensitive to both cadmium and copper. X-ray microanalysis of root tip sections showed that copper and cadmium only accumulated in the root tips of F. angustifolia, copper mostly in the cell walls of the cortex layer, cadmium in the inner compartments of the cortex cells. It is suggested that in the two Pinus species the well developed root cap plays a protecting role against metal uptake at the root-tip zone.