With the rapid development of nanotechnology, iron nanoparticles have been used widely in multiple industrial, commercial, and biomedical applications to benefit society. Because of their high reactivity and magnetic property, iron nanoparticles have also been suggested as high-efficiency remediation agents for environmental applications [1], but its impacts on plants are still not very clear. In this research, the influence of different concentrations (0, 50, 100, 200, 400 and 800 μg/mL) of zero-valent iron nanoparticles (nZVI) on seed germination parameters including germination percentage (GP %), mean germination time (MGT), germination rate (GR), germination index (GI) and seedling vigor index (SVI) were evaluated under in vitro conditions. Results showed that significant (p < 0.05) differences in examined traits were observed among the employed nZVI concentrations. The highest (92.4%) and the lowest (56.8%) GR were observed in seeds exposed to 50 and 800 μg/mL nZVI concentrations, respectively. The minimum MGT (2.25 day) was observed in seeds treated with 200 μg/mL nZVI concentration. Moreover, application of nZVI at high doses (400 and 800 μg/mL) significantly (p< 0.05) diminished the root and shoot lengths by 46.8% and 52.3% in comparison to the control, respectively. Also, the highest GI value (6.14) was found at 100 μg/mL nZVI. Moreover, the highest SVI (752.3) was observed at 200 μg/mL of the reference treatment. In conclusion, application of appropriate levels of nZVI stimulates the seed germination attributes of D. stramonium. The mechanisms by which nanomaterials facilitate seed germination are not fully understood yet. However, it has been suggested that they can penetrate seed coats and create new pores, which subsequently allow the entry of water, oxygen, nutrients and external molecules in the germinating seeds. Such pores behave as scarification process at the microscopic scale. In another mechanism assumed that nanotubes affect the water channel (
