engleski

Evaluation of phytotoxic and genotoxic effects of surface waters using duckweed (Lemna minor L.)

Due to the enormous number of potentially polluting substances contained in surface water, a chemical-specific approach is insufficient to provide the information about water quality. Therefore it is essential to use biological test systems with living cells or organisms that give a global response to the pool of micropollutants present in the sample. The aim of this study was to evaluate and compare the suitability of certain endpoints: growth parameters, pigment content, peroxidase activity, lipid peroxidation and alkaline comet assay as biomarkers for environmental monitoring of surface waters using duckweed plants as a test system according to the standardized protocol ISO 20079. Duckweeds (Lemnaceae) possess physiological properties (small size, high multiplication rates, and vegetative propagation), which make them an ideal test system. Moreover, duckweed can be used in a wide range of pH-values (pH 3.5-10). In the proposed test protocol, plants are exposed to a toxicant over a period of seven days, when the consequent potential growth inhibition based on frond number and biomass is estimated. The surface waters were collected monthly over a three-month period at three sampling sites along the river Sava and its confluents (Croatia). The pH value of all samples was in the range 7.8– 8.0. All samples caused inhibition of growth rates derived from frond (leaves) number, decrease of chlorophylls content and of peroxidase activity. Contrary to that, dry to fresh weight ratio markedly increased in duckweed exposed to tested water samples. Tail extent moment (measure of DNA strand breaks) and lipid peroxidation (measure of biomembrane injury) showed increase only in more polluted water samples. In the present study frond number and final biomass proved to be almost equally sensitive parameters, followed by dry to fresh weight ratio, peroxidase activity and chlorophyll a and carotenoid contents. Simplified Comet procedure modified for plants tissues allows rapid yet sensitive determination of DNA damage. The results obtained suggest that phyto- and genotoxicity tests with Lemna minor should be used in the biomonitoring of municipal, agricultural and industrial effluents because of their simplicity, sensitivity and cost-effectiveness.

Lemna minor; aquatic plant; comet assay; chlorophyll; toxicity

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