Effect of Copper on the Toxicity and Genotoxicity of Cadmium in Duckweed (Lemna Minor L.)

Petra Cvjetko,Željka Vidaković-Cifrek,Mirjana Pavlica,Biljana Balen,Mirta Tkalec,Sandra Šikić,Sonja Tolić

doi:10.2478/10004-1254-61-2010-2059

Petra Cvjetko, Željka Vidaković-Cifrek + Show 5 more

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https://doi.org/10.2478/10004-1254-61-2010-2059

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Abstract

We investigated interactions between copper (in the concentrations of 2.5 μmol L-1 and 5 μmol L-1) and cadmium (5 μmol L-1) in common duckweed (Lemna minor L.) by exposing it to either metal or to their combinations for four or seven days. Their uptake increased with time, but it was lower in plants treated with combinations of metals than in plants treated with either metal given alone. In separate treatments, either metal increased malondialdehyde (MDA) level and catalase and peroxidase activity. Both induced DNA damage, but copper did it only after 7 days of treatment. On day 4, the combination of cadmium and 5 μmol L-1 copper additionally increased MDA as well as catalase and peroxidase activity. In contrast, on day 7, MDA dropped in plants treated with combinations of metals, and especially with 2.5 μmol L-1 copper plus cadmium. In these plants, catalase activity was higher than in copper treated plants. Peroxidase activity increased after treatment with cadmium and 2.5 μmol L-1 copper but decreased in plants treated with cadmium and 5 μmol L-1 copper. Compared to copper alone, combinations of metals enhanced DNA damage after 4 days of treatment but it dropped on day 7. In conclusion, either metal given alone was toxic/genotoxic and caused oxidative stress. On day 4 of combined treatment, the higher copper concentration was more toxic than either metal alone. In contrast, on day 7 of combined treatment, the lower copper concentration showed lower oxidative and DNA damage. These complex interactions can not be explained by simple antagonism and/or synergism. Further studies should go in that direction.

Highlights

Peroxidase activity increased after treatment with cadmium and 2.5 μmol L-1 copper but decreased in plants treated with cadmium and 5 μmol L-1 copper
Interest has been focused on using aquatic plants, such as Lemna minor, Microspora, and Pistia stratiotes, as a promising approach to take up heavy metals from water body [18, 19]
10 colonies of healthy duckweed were transferred into a 300 mL Erlenmeyer flask containing 100 mL of Steinberg nutrient solution with Cd at the concentration of 5.0 μmol L-1 and/or Cu at 2.5 μmol L-1 or 5.0 μmol L-1

Summary

Introduction

We investigated interactions between copper (in the concentrations of 2.5 μmol L-1 and 5 μmol L-1) and cadmium (5 μmol L-1) in common duckweed (Lemna minor L.) by exposing it to either metal or to their combinations for four or seven days. On day 7 of combined treatment, the lower copper concentration showed lower oxidative and DNA damage These complex interactions can not be explained by simple antagonism and/or synergism. At high concentrations it inhibits root growth, induces chlorosis, necrosis, and leaf discoloration, and disturbs very important cell processes [11] It can damage cell membranes and induce lipid peroxidation since Cu, like other heavy metals, induces oxidative stress [12, 13].

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