Influence of nickel (Ni) excess on selected physiological aspects of Matricaria chamomilla metabolism after 10 days of presence was studied. Biomass, water content, assimilation pigments and lignin contents were not affected by any of the doses tested. High Ni doses elevated root-soluble proteins. The highest Ni concentration stimulated accumulation of soluble phenolics in both the rosettes and roots, and hydrogen peroxide in the roots. Malondialdehyde content was unaltered, but proline content increased more pronouncedly in the rosettes. Histidine was elevated in the roots, suggesting its involvement in Ni retention. Roots contained 3.4, 7.3 and 6.1 times more Ni than leaf rosettes with 3, 60 and 120 microM treatments, indicating that chamomile is a Ni excluder. Leaf rosettes accumulated 174.1 microg Ni g(-1) DW at 120 microM treatment. The results suggest chamomile tolerance to Ni excess and its considerable accumulation in above-ground biomass (ca. 30% of whole plant Ni content).