Toxicity of nanosilver and fumonisin B₁ and their interactions on duckweed (Lemna minor L.)

In the environment co-contamination of several toxicants commonly occurs. However, toxicological studies usually are focused on only one toxicant. The aim of this study was to investigate toxicity of silver nanoparticles (AgNP)and mycotoxin fumonisin B₁ (FB₁)and their possible interactions as well as to explore tentative mechanism of their toxic effect. Duckweed (Lemna minor L.)was treated with AgNP or FB₁ (at concentrations 0.5 and 1.0 mg L⁻¹)or with their combination at same concentrations for 3 days. Both AgNP and FB₁, applied individually significantly affected levels of certain nutrients, reduced growth rate and the levels of photosynthetic pigments though AgNP at a much greater extent compared to FB₁. Furthermore, AgNP induced ROS generation, lipid peroxidation and increase of antioxidative enzymes activities, while FB₁ induced changes only in the activities of antioxidative enzymes. Those results implicate that phytotoxicity of both AgNP and FB1 can be associated with imbalance of mineral and cell redox status. However, toxic actions of AgNp singly applied were more pronounced. Combined treatment with AgNP and FB₁ produced higher degree of changes in all parameters than corresponding concentrations of AgNP or FB₁ alone implying their additive effects. Additionally, higher level of FB1 found in medium, and higher level of intracellular Ag following combined treatment indicates interaction of two toxicants at the transport level/uptake in the cell which resulted in higher accumulation of Ag in duckweed cells. The latter in turn exerted higher toxicity to duckweed compared to single treatment of AgNP.