Assessment of the level of water pollution is an important component of pollution monitoring. Rivers are polluted by sewage from enterprises and it is often difficult to assess the level of pollution and toxicity of the surface waters. Usually chemical methods of research are time-consuming and expensive. Methods of biotesting and bioindication can give a quick and accurate answer about the toxicity of waters. Nowadays, integrated methods are needed to assess the level of water pollution and water toxicity, especially in regions with a well-developed industry, where there are rivers that experience anthropogenic pollution. In many researches special attention is given to the study of low-molecular antioxidants as biochemical indicators of environmental pollution as well as biomarkers of the physiological condition of the plants growing under stressful environmental conditions. Lemna minor is an interesting plant which is available as a bioassay. It is widely spread, can be easily cultivated and is sensitive to contamination by heavy metals. The purpose of the work was to identify the specific effects of heavy metal salts (Zn, Cd, Ni, Co, Cu, Fe, Sr) on the Lemna minor L. culture in order to assess the possibility of using Lemna minor as a bioassay.The duckweed plants were grown on Steinberg nutrient medium. Lemna minor was grown in heavy metal solutions of different concentrations (0.05; 0.5; 5.0 and 25 μM/l) in three biological replications. Сontent of free proline in plants was determined with acid ninhydrin reagent by Bates' method. (Bates et al., 1973). It has been established that heavy metals concentration of 0,05 to 0,5 and 5 µmol/l gradually increases the concentration of proline in leaves. While the concentration of metals of 25 µmol/l causes drastic increase of proline content in Lemna minor plants. Concentration of proline in the plants grown in the solutions containing 0,05 µmol/l of cadmium and strontium surpassed the control option. The highest content of proline was observed in plants under the concentration of 5 µmol/l for nickel, zinc and strontium. The concentration of metal ions 25 μmol/l gave a high content of proline in plants cultivating in solutions with cobalt, strontium, copper and nickel. The results of the researches give grounds to recommend Lemna minor as a test organism, using proline content as a biomarker of the physiological state of plants.
ryaska, prolin, tyazhelye metally, biomonitoring, biotestirovanie, bioindikaciya
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