engleski

Physiological response of Lemna gibba L. when exposed to ionic colloidal silver

Duckweeds are widely distributed aquatic vascular plants with many advantages as test organisms. Due to their small size and simple structure, they are easily cultivated in the laboratory conditions. Lemna plants are representatives of primary producers in several standardised protocols (ISO, OCED and US EPA) for determining phytotoxicity of different environmental chemicals in aquatic ecosystems. Silver is a non- essential element for living organisms and one of the most toxic metals in aquatic ecosystems. It is now recognised that silver concentration in the biosphere is increasing due to anthropological activities such as photographic industry, electronics and electrical applications, and nowadays, nanotechnology. The aim of this study was to determine physiological changes in duckweed Lemna gibba L. induced by treatment with ionic colloidal silver in full strength Pirson-Seidel’s nutrient solution and in nutrient solution with decreased nitrogen and phosphorus concentrations. Silver accumulation in plants disrupted nutrient balance, caused damage to photosynthetic apparatus, oxidative stress and growth inhibition. Oxidative stress, evident from increased accumulation of hydrogen peroxide and lipid peroxidation end-products, indicated an insufficient antioxidative response of L. gibba plants. The intensity of oxidative stress depended on the concentration of ionic colloidal silver as well as the duration of exposure. Although the accumulated silver concentrations were lower, silver was toxic to L. gibba plants in nutrient solutions with decreased nitrogen and phosphorus concentrations. Observed physiological changes in L. gibba plants were the result of silver toxicity, since decreasing nutrient concentrations to 50% and 25% in the medium did not cause significant oxidative stress. In plants treated with ionic colloidal silver in the nutrient solution with 10% of nitrogen and phosphorus combined effect of metal toxicity and decreased nutrient concentration was evident.

model organism, silver, nutrient, oxidative stress, synergistic effect

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