Impact of herbicide use on the metabolism of Brassica napus L. as feed and energy crop, in function of its quality and potential use for phytoremediation (Research)
The increasing demand for food, water and energy in our current society presents us with major issues about the future. In order to secure food supply, pesticides play an essential in the agronomical sector. But the worldwide use of pesticides goes hand in hand with the exposure to potentially dangerous chemicals and lightens up questions about food and environmental safety. Herbicides, which make up 48% of the pesticide consumption, comprehend active ingredients, which belong to the class of organic contaminants. These compounds often are chlorinated and can therefore induce long-term harm to humans and environment via bioaccumulation. The active ingredients inhibit plant specific plant processes such as photosynthesis, biosynthesis of the cell wall, lipids and amino acids. The selectivity of the active ingredient is therefore crucial to assure suppression of weeds without affecting crop yield and quality. A key role in crop toleration against herbicides is the plant metabolism, which stands in for detoxification of xenoviotics. The plant detoxification process can be divided into three steps. Cytochrome P450 enzymes and peroxidases will primarily convert the active ingredient into a more polar structure, which can in turn conjugate with glutathione (GSH) via glutathione-S-tranferases (GST). Finally, this metabolite complex will be transferred to the vacuole or the apoplast, were it is biological inactive. The focus in this project is rapeseed (Brassica napus), an important crop for oil production and a potential source for biofuel. The first part of this thesis contains an in situ field and mesocosm experiment where I investigate the fytotoxicity of the selective herbicide metazachlor and the residual herbicides mesotrione and terbuthylazine in the crop B. napus. De effects of herbicides will be studied on morphological (biomass, seed production), physiological (lipid peroxidation, pigment analysis and nutrient profile) and biochemical level and will be linked to the cellular redox balance (presence and activity of enzymes and metabolites). In the second part the underlying mechanisms of tolerance, the metabolism, which exists of detoxification and redox processes, in B. napus and its related model plant Arabidopsis thaliana will be invesitgated. I will study the role of the cellular redox balance (pro- and antioxidants) and the role of GST enzymes on transcriptional and protein level. Insights in the defence mechanisms against herbicide treatment can contribute to the development of more selective and therefore less harmful herbicides, so that biomass production and quality can be assured. This knowledge can be helpful selecting suitable plant varieties according to their goal; use as feed/food or use as phytoremediation crop with energy as final product. Phytoremediation is a low-cost, environmental friendly and safe alternative for soil purification that contributes to development of new strategies to ensure yield and quality of agronomical sector in a changing environment.
Period of project
01 January 2012 - 31 December 2015