The relationship between metal uptake, antioxidant enzyme activities, and membrane lipid peroxidation level (LPO) in Fusarium equiseti and F acuminatum grown in media with different iron and manganese concentrations was investigated with respect to incubation period. Increasing the iron concentration (1-20 mu M) in the culture medium of the Fusarium species resulted in steady increases in intracellular iron levels and steady decreases in magnesium and zinc levels, whereas intracellular manganese levels rose until Fe2+ concentration reached 3.7 mu M and decreased significantly at 20 mu M Fe2+. Intracellular manganese and magnesium levels increased with respect to increase in manganese concentration (2.5-30 mu M) of the culture medium although zinc level did not change significantly. Intracellular iron levels increased up to an Mn2+ concentration of 5.9 mu M and then decreased with further increase in manganese concentrations as well as the response of iron. Superoxide dismutase (SOD) activities of both of the Fusarium species reached their maximum values at 3.7 mu M Fe2+ at which concentration intracellular manganese contents also increased. At higher iron concentrations in the medium, intracellular manganese levels and SOD activities decreased while iron contents continued to increase. Catalase (CAT) activities of these Fusarium species reached their respective maximum values at 3.7 mu M Fe2+. The highest levels of SOD and CAT activities of F. equiseti and F. acuminatum were found in the medium containing 5.9 mu M Mn2+ except for SOD activity of F. acuminatum which had a maximum value in the medium containing 30 mu M Mn2+. As an indicative marker of oxidative damage, LPO levels of both Fusarium species showed negative correlation with SOD and CAT activities. Maximum LPO levels were found where minimum antioxidant enzymes and maximum iron contents were observed in the cells. (c) 2004 Elsevier Ltd. All rights reserved.