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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

Book - Dissertation

The aim of this study was first to investigate uranium toxicity effects and to unravel mechanisms by which plants respond to uranium stress. In a next phase, the influence of secondary stressors on uranium induced effects was investigated. The highest uranium concentration of 100 ┬ÁM 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 antioxidative defense, suffering from severe oxidative stress with a completely disturbed metabolic balance. While at lower uranium concentrations no oxidative stress related responses are visible in roots, leaves show an increased defense against uranium stress with an important regulatory role for the ascorbate pool as an early and stable stress response mechanism. Arabidopsis thaliana plants are therefore able to defend themselves under moderate environmental uranium contamination conditions although responses differ for leaves and roots. Toxicity effects during mixed exposure were mostly due to cadmium, indicating its higher toxicity in comparison to uranium for the concentrations applied. Nevertheless, uranium induced similar effects and worked at similar sites of action. Therefore, when uranium is present in combination with cadmium or probably also other heavy metals, uranium induced effects will be influenced. As gamma radiation was already applied in a relatively high dose and only minor effects could be ascribed to it, gamma radiation induced effects can be considered negligible when during environmental realistic situations uranium exposed plants are simultaneously irradiated.