The role of antioxidative enzymes in copper tolerance strategy of Mimosaceace prosopis farcta growing in a copper mine
In this study, we determined the accumulation levels of copper in tissues and the status of antioxidant enzyme activities in Mimosaceace prosopis fracta against Cu-toxicity in a copper mine. We measured the level of chlorophyll and the activities of superoxide dismutase, glutathione peroxidase and catalase by spectrometry, malondialdehyde and dityrosine by HPLC and the levels of Cu in tissues and soils by atomic absorption spectrometry. Total and available copper were at toxic levels for plants growing in contaminated soil (zone 1). However, there were no visual or conspicuous symptoms of Cu-toxicity in plant species. Excess copper was transferred into C. ambrosioides tissues. The Mimosaceace prosopis fracta accumulated Cu in roots and then in leaves, in which the leaves’ chloroplasts stored Cu to approximately two times that of vacuoles. In zone 1, the chlorophyll levels increased significantly in leaves of Mimosaceace prosopis fracta with respect to the same plant growing in uncontaminated soil (zone 2). The studied plants in zone 1 revealed a significant increase in tissue antioxidant enzyme activities in comparison with the same plants in zone 2. The levels of oxidative damage biomarkers of lipids, such as MDA and proteins such as dityrosine, were higher in tissues of Mimosaceace prosopis fracta that were grown in zone 1 as compared to the same plant species in zone 2, though this difference was not significant. The levels of these biomarkers were higher in roots, stems and leaves, respectively, in both zones. There were significant differences between roots and leaves for these parameters. We concluded that elevation of antioxidative enzyme activities was a tolerance strategy in the studied plants that protected them against copper toxicity.
