Higher toxicity of nano-scale TiO2 and dose-dependent genotoxicity of nano-scale SiO2 on the cytology and seedling development of broad bean Vicia faba

Abstract

Since nanotechnology entered the field of agriculture, its safety impact on crops has been a high priority interest. Here, we aimed to evaluate the effect of two different types of nanoparticles (n-), n-SiO2 and n-TiO2, on the above- and below-ground growth and the root-tip cell mitosis of broad beans (Vicia faba L.), one of the major carbohydrate food sources as well as an ecotoxicological model plant. Seeds were soaked in n-SiO2 and n-TiO2 each at different concentrations (25, 50 and 75 mg/L) for 24 h. Nano-TiO2 decreased vigor index, reflecting shorter shoots at all concentrations studied. By contrast, germination percentage and root length were not affected by any treatments. Cytological analysis suggested no significant difference in mitotic index (index for cell division activity) from the control. However, total chromosomal aberrations (%) were increased dose-dependently by n-SiO2 and dose-independently by n-TiO2. Also, different types of chromosomal abnormalities were induced by the nanomaterials; n-SiO2 induced bridges at 50 and 75 mg/L, whereas n-TiO2 induced breaks at 50 mg/L. In addition, cells in prophase were more frequently observed and those in anaphase less frequently seen with decreasing n-SiO2 concentrations. We concluded that n-TiO2 was more toxic than n-SiO2 for broad bean chromosomes and early plant development at the concentrations studied. Finally, our review indicates the lack of evidence of germination enhancement by n-TiO2 in Poaceae, a large monocotyledon family, which may require further attention.