Effect of Metal Oxides on Plant Germination: Phytotoxicity of Nanoparticles, Bulk Materials, and Metal Ions

Abstract

The recent rapid expansion of nanotechnologies has increased concern over the impact of engineered nanoparticles (ENPs) on the environment and biota. Although the toxicity of ENPs has received considerable attention in the recent years, there are still gaps in our knowledge of the mechanisms responsible for their effects. In this study, we tested the toxicity of various metal oxide ENPs (Al2O3, CuO, Fe3O4, MnO, TiO2, and ZnO), including nanowires together with their bulk counter particles and soluble metal salts, on germinating seeds of Sinapis alba L. Fe3O4, TiO2, MnO2, and Al2O3 ENPs did not negatively affected seed germination at any tested concentrations. However, CuO and ZnO ENPs showed a dose-dependent inhibition of germination. Metal ions were more toxic than metal oxide particles at corresponding concentrations. The highest toxicity was exhibited by Cu, followed by Zn, Fe, Al, and Mn ions. A comparison of ENPs with bulk materials did not reveal significantly higher ENP toxicity. Similarly, nanowires showed effects similar to other nanoparticles and bulk materials. Our results indicate that the nanosize or shape of particles did not play a crucial role, whereas metal ions released into cultivation media and accumulated in seedlings contributed significantly to the phytotoxicity of metal oxides.