Immuno-gold electron microscopical detection of the nucleolar protein nucleolin. A) Portions of nucleoli from root meristematic cells, labelled with anti-nucleolin antibody and visualised with colloidal gold particles, are shown for the 2-day experiment: (left) 0 g* samples, (right) external 1 g control samples. Nucleolin is localised in the dense fibrillar component (DFC), surrounding fibrillar centres (arrows) in both cases. The 0 g* sample shows a lower density of gold particles, indicating a lower nucleolus activity. B and C) Density of immunogold particles measured after two- (B) and four-day long (C) experiments. Statistically significant differences in density (p < 0.05), compared to the control, are indicated with a ‘§’ symbol when compared with the 1 g external control, and with ‘#’ when compared with the 1 g* control.