Effects of different concentrations of Al on nucleoli in root tip cells of P. massoniana . Arrowhead shows argyrophilic proteins. A. Control cells. B. Showing the irregular nucleolus (10-5 M Al, 72 h). C. Some particles containing argyrophilic proteins scattered in the nucleus (10-4 M Al, 24 h). D. Large amounts of argyrophilic proteins in nucleus with prolonging treatment time (10-4 M Al, 48 h). E-G. Argyrophilic proteins leaching from the nucleus to the cytoplasm and more and more argyrophilic proteins accumulated in the cytoplasm with prolonging the duration of treatment (E.10-4 M Al, 48 h; F-G. 10-4 M Al, 72 h). H-J. Showing the argyrophilic proteins enclosed the nucleus, and accumulated in the cytoplasm and occupied nearly the whole cytoplasm (H. 10-3 M Al, 72 h; I. 10-2 M Al, 72 h; J. 10-2 M Al, 72 h). K. In long cells, the argyrophilic proteins gathered at the cell ends (10-2 M Al, 24 4h). L. Argyrophilic proteins scattered in the nucleus, appearing small in size and weak in silver staining reaction (10-2 M Al, 24 h). Scale bar =10 μm.