Figure 4: TEM micrographs showing internalization and sub-cellular damage in A. cepa root meristem cells upon exposure with ZnO-NPs.
Untreated cell showing normal architecture of nucleus (N), nucleolus (n), integrated mitochondria (M), intact nuclear membrane (Nm), vacuoles (V), plasmodesmata (P) (panel A and B). Triangular periplasmic space is clearly visible in untreated cell (panel B). Magnified view of nuclear matrix and nucleolus of untreated cell (panel C and D). Images of roots treated with ZnO-NPs (1000 μg/ml) showing the influx of ZnO-NPs in cytoplasm and attachment to the vacuoles (panel E). Yellow arrow heads showing degeneration of nuclear constituents and significant swelling of mitochondria while red arrows and arrow heads showing attachment of ZnO-NPs onto the nuclear membrane and infiltration of ZnO-NPs in intracellular junctions (panel F). Analysis was performed at 200 keV. Magnified view showing the sequesteration of ZnO-NPs on nuclear membrane (panel G). Distribution of ZnO-NPs in cytoplasmic matrix (panel H). Magnification for images (panel A) 10,000x, (panel B) 30,000x, (panel C) 12,000x, (panel D) 20,000x, (panel E) 15,000x, (panel E inset) 20,000x, (panel F) 15,000x, (panel G) 20,000x, (panel G inset) 30,000x, (panel H) 20,000x, and (panel H inset) 25,000x.
