Since it is unknown how different U species determine U uptake and translocation within plants and how they might affect the oxidative defence mechanisms of these plants, this study aimed to analyse U uptake and oxidative stress related responses of different U species in Arabidopsis thaliana plants (Columbia ecotype). Eighteen-day-old seedlings were exposed for three days to 25 µM U in a Hoagland nutrient solution of which the pH was adjusted to 4.5, 5.5, 6.5 or 7.5. Results indicate that there is a different rate in U uptake and translocation at the different pHs, with high uptake and low translocation at low pH and lower uptake but higher translocation at high pH. After U exposure, an increased glutathione reductase activity and total glutathione concentration were observed in U-exposed roots, pointing towards an important role for glutathione in the root defence system against U either by chelation (phytochelatin production) or antioxidative defence mechanisms (cellular redox state). In the leaves, the antioxidative defence mechanisms were activated upon U exposure, indicated by an increased superoxide dismutase and catalase activity.