Effects of cadmium, lead and chromium (VI) on the activities of enzymes of antioxidant system in the cells of duckweed (Lemna minor L.)

O. Bubys, H. Antonyak

Ivan Franko National University of Lviv
4, Hrushevskyi St., Lviv 79005, Ukraine

The results of studies of the effect of cadmium (Cd), lead (Pb) and hexavalent chromium (Cr (VI)) on the activities of enzymes of antioxidant system (superoxide dismutase, catalase) in the cells of duckweed (Lemna minor L.) under cultivation in laboratory conditions are presented in the article. Content of investigated elements in the cultural medium corresponded to the value of 1–50 maximum allowable concentrations (MAC). It was established that the dynamics of enzymatic activity in plant cells depended on the concentration of the elements in the aquatic environment. In the presence of Cr (VI), Cd and Pb in the range of concentrations 1–4 MAC, 1–10 MAC and 1–20 MAC, respectively, the activities of antioxidant enzymes in the cells of duckweed increased. However, superoxide dismutase activity in duckweed cells was inhibited by cd and Cr (VI) in concentrations, respectively, 50 MAC and 20–50 MAC, and catalase activity was inhibited by these elements in concentrations, respectively, 20–50 MAC and 10–50 MAC. Lead in the range of investigated concentrations had no inhibitory effect on the activity of superoxide dismutase, and catalase activity was inhibited by 50 MAC of Pb. In general, tolerance of antioxidant enzymes in duckweed to the exposure by studied elements decreased in the order: Pb > Cr (VI) > Cd. The obtained results suggest that the stability of the antioxidant system of duckweed cells to inhibitory action of Cd, Pb and Cr (VI) can play an important role in remediating properties of Lemna minor L. and in its capacity for accumulation of these elements from aqueous environment at a significant concentration range.

Keywords: duckweed, Lemna minor L., cadmium, lead, chromium (VI), maximum allowable concentration, antioxidant system, superoxide dismutase, catalase

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