Study of biological effects induced in Arabidopsis thaliana following uranium exposure, including mixed exposure to cadmium or external gamma radiation: applying a multi-biomarkers approach

The first objective of this thesis concerned studying uranium induced toxicity effects in Arabidopsis thaliana and investigating the role of oxidative stress as a modulator during uranium stress. It can be concluded that 100 µM uranium is extremely toxic for Arabidopsis thaliana plants with a completely inhibited growth, a fully disturbed nutrient profile, wilting and although making an effort to increase the antioxidative defense, suffering from severe oxidative stress with a completely disturbed metabolic balance. While at lower uranium concentrations no oxidative stress related responses were visible in the roots, leaves showed an increased defense against uranium stress with an important regulatory role for the ascorbate pool as a stable stress response mechanism. Arabidopsis thaliana plants are therefore able to defend themselves under moderate environmental uranium contamination conditions. The second objective of this thesis concerned studying the influence of a secondary stressor such as cadmium or external gamma radiation on uranium toxicity effects in Arabidopsis thaliana plants. Under mixed exposure, results indicated that uranium toxicity effects were highly influenced by cadmium while the influence of gamma radiation could be considered negligible.