On the nature and timing of oxygen radical production following exposure of Arabidopsis thaliana leaves to uranium, cadmium or a combination of both stressors.

Here the toxicity and oxidative stress responses of Arabidopsis seedlings induced by 238U and Cd alone or in a multi-pollution set-up are studied in function of time. After 48h a significant decrease in root and shoot growth was evident in all treated plants. The equitoxic mixture of 238U and Cd behaved according to concentration addition for biomass accumulation. Production of O2.- was only significantly measurable after 48h treatment which coincides with a significant decrease in biomass production and probably also plant cell death. For Cd but not for 238U or 238U+Cd treated plants, H2O2 production increased from 24h onwards. In addition the antioxidative capacity, both water and lipophilic (acetone) soluble antioxidants, significantly increased in 238U treated plants after 48h. In contrast for Cd treated plants only after 7d a significant increase in water soluble antioxidants was measured whereas and no difference in the acetone extractable fraction was visible. In conclusion both 238U and Cd adversely affect growth and this is accompanied by an oxidative stress response. Whereas for Cd an increased ROS production was detectable after 24h a similar oxidative burst in 238U treated plants might be masked by the presence of a higher antioxidative capacity.