THE EFFECT OF HEAVY METAL IONS ON THE PEROXIDASE ACTIVITY IN ARABIDOPSIS THALIANA

Abstract

The biosphere pollution with the heavy metals (HM) has increased significantly in recent decades due to human activity. Plants can accumulate and concentrate HM, which negatively affects their growth, productivity and quality of agricultural products. Some HM, such as copper, belong to the group of biogenic elements that, in low concentrations, are essential for the normal functioning of plant organisms. Other HM such as cadmium are toxic even in low concentrations. The toxicity of HM is related to oxidative damage. In the plant cell, the antioxidant system provides protection against this kind of stress. However, data on changes in antioxidant enzyme activities in the early stage of the cellular response to HM-induced stress remain scarce. Therefore, we focused our research on studying peroxidase (POD) activity changes in Arabidopsis thaliana under conditions of rapid uptake of copper and cadmium ions into leaf tissue. For the experiments, 4.5–5-week-old A. thaliana plants were used. The plants were incubated on 0.5x MS liquid medium containing copper or cadmium chloride at concentrations of 0.1, 0.5 and 5 mM. The HM salt treatment was carried out in the dark at 20 °C for 2 (short-term stress) and 12 (long-term stress) hours. After that, the leaves were frozen and the POD activity was measured. Evaluation of the effects of Cd2+ and Cu2+ ions shows that these HM cause a decrease in POD activity after 2 hours and its increase after 12 hours of treatment. Therefore, modulation of POD activity is a component of the HM stress response in A. thaliana. Analysis of the available data revealed that the enzymes POD and CAT, which eliminate hydrogen peroxide, can partially replace each other and thus provide cellular protection in different phases of the stress response.