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

Belgian Nuclear Research Centre (SCKCEN), Biosphere Impact Studies, Boeretang 200, 2400 Mol, Belgium

Abstract

The toxicity and oxidative stress responses of 19-day old Arabidopsis seedlings induced by U (66 μM) and Cd (20 μM) alone or in a binary mixture set-up (equitoxic mixture) are studied in function of time. After 48h a significant decrease in root and shoot growth and a simultaneous increase in anthocyanin production was evident in all treated plants.

Production of O⁻₂ or H₂O₂ was visualized by staining freshly harvested leaves with nitrobluetetrazolium or diaminobezidine, respectively. With this method production of O⁻₂ was only significantly measurable after 168 h treatment which coincides with a significant decrease in biomass production and probably also plant cell death. For Cd treated plants a significant increase in H₂O₂ production was measurable from 24h onwards. In contrast, a similar H₂O₂ production could not be measured in U or U + Cd treated plants. Both water and lipophilic soluble antioxidants significantly increased in U treated plants after 48 h. These high antioxidant levels might detoxify potential H₂O₂ produced in the U treated plants. In contrast for Cd treated plants only after 168h a significant increase in water soluble antioxidants was measured whereas no difference in the lipophilic fraction was visible.