Chapter 8: Ecotoxicity, Oxidative Stress and Phytoremediation of Nickel on Aquatic Plants

The search for environmentally friendly practices and new technologies in order to reduce the ecological impact associated with nickel disposal and pollution remains open. In this sense, phytoremediation stands out as a high-efficiency, eco-friendly green technology for removing pollution from contaminated soil, water and air. It is a form of bioremediation and an economical and sustainable alternative to traditional chemical and physical pollution remediation methods. High metal bioaccumulation efficiency and tolerance are requisites for plants employed in phytoremediation techniques; thus, investigating new aquatic plants with such characteristics is a priority. The antioxidant defence system plays a significant role in providing resistance to plants by protecting labile macromolecules against the attack of free radicals. This ability made possible the use of aquatic plants in technological applications for the restoration of contaminated sediments, solid wastes and organic contaminants. Accordingly, results have demonstrated that Lemna gibba and Ceratophyllum demersum would have the capacity to tolerate and, therefore, resist nickel stress. APX would be a more efficient enzyme in the detoxification of hydrogen peroxide, as its activity was stimulated at higher exposure concentrations. This reinforces the proposal of selecting APX as a good biomarker for the evaluation of the welfare of plants and growth performance. It is important to keep in mind that plant stress tolerance may be improved by the enhancement of the levels of antioxidant enzymes, in particular those related to the application of aquatic plants in the phytoremediation of nickel from wastewaters and industrial effluents.