PROTON MICROPROBE AND X-RAY-FLUORESCENCE INVESTIGATIONS OF NICKEL DISTRIBUTION IN SERPENTINE FLORA FROM SOUTH-AFRICA

Certain plant species growing on serpentinite soils are hyperaccumulat ive of Ni. The ability to tolerate high Ni levels may have useful envi ronmental and economic implications. However, the processes of Ni accu mlulation and tolerance are not well understood. The proton microprobe of the Schonland Research Centre was used in the PIXE mode to map the lateral and cross-sectional distribution of Ni and other elements in the tissue of species from the family Asteraceae, growing on serpentin e outcrops in the Barberton district, south-eastern Transvaal. Element al maps showed that the highest Ni enrichment was in the epidermis. En ergy dispersive XRF fluorescence analysis was used for qualitative rap id scanning to select suitable metal-rich plants and for quantitative bulk analyses.