Determination of toxic effects of biologically synthesized silver nanoparticles on the aquatic plant Lemna minor

Silver nanoparticles (AgNP) are nowadays widely used in many different sectors. It is inevitable that these particles are released to the environment during production, use and disposal. Therefore, it is important to evaluate the toxicity of the organisms, especially in the aquatic environment. In this study, subacute toxicity of AgNPs obtained by phytosynthesis was investigated using Lemna minor L. plant. Lemna minor L. plant stock cultures, which have a high sensitivity to the effects of pollutants, were grown in the climate room according to OECD 221 guidelines. After 8 weeks of acclimation in Steinberg media, the plants were treated with different concentrations of AgNP for 14 days. The formation of silver nanoparticles obtained by laurel (Laurus nobilis L.) extract was determined by UV-VIS spectrophotometric measurements. The AgNPs synthesized by the phytosynthesis method were characterized by Fourier transform infrared spectroscopy (FTIR), Zeta size and potential, Inductively Coupled Plasma Mass Spectrometry and Scanning electron microscopy (SEM) analysis. The analysis results show that AgNPs are homogeneously distributed, spherical in shape with an average size of 102 nm and coated with phyto-content. The increase in AgNP concentration applied to Lemna minor plants caused a decrease in the number of leaves and growth rate of the individuals. The results showed that the EC50 value of AgNP synthesized by the phytosynthesis method was 4.78 mg/L and no observed effect concentration (NOEC) was 0.1 mg/L. According to these results, even if produced by phytosynthesis, AgNP release into water causes growth inhibition on Lemna minor and thus poses a toxicological risk.