Toxic effects of silver nanoparticles on the germination and root development of lettuce (Lactuca sativa)

摘要

The advancement of nanotechnology has increased use of nanoparticles in industrial scale. Among the most used nanoparticles are those silver-based. Large-scale use can raise levels of these nanoparticles in aquatic environments, which, in turn, presents potential risks to aquatic organisms and ecosystems, causing undesired environmental impacts. To evaluate the potential risk of the silver nanoparticles (AgNPs) interaction with plants, seeds of Lactuca sativa L. (Asteraceae) were exposed to different concentrations of AgNPs (12.5, 25, 50, 100 ppm), using the percentage of germinated seeds and morphological changes in the root as toxicity criterion. Only at the maximum concentration of AgNPs (100 ppm), there is a negative effect on root growth in relation to the positive control (distilled water). These negative effects may be related to the production of reactive oxygen species (ROS) caused by the dissolution of Ag-0 in Ag+. Other concentrations had a positive effect on root growth, although not significant. Scanning electron microscopy (SEM) images showed morphological changes in the root surface exposed to the concentration of 100 ppm of AgNPs, resulting in root deformation. The accumulation of silver nanoparticles (AgNPs) was observed using transmission electron microscopy (TEM). AgNPs were found in the vacuoles, cell wall, middle lamella and cytoplasm, individualised or forming agglomerates. These results broaden our understanding of the safe levels of nanoparticle use and its impact on the environment. In addition, the nanoparticles used in this study can be used in new product development, since the observed maximum safe amount.