The spots were localized mainly on the plasmalemma (Figure 1A,B, arrows). Small Ag particles were also found on the cell wall of the xylem vessels, in the cell lumen (Figure 1C, arrows) and in areas corresponding to the pits (P in Figure 1D, arrows). The ultrastructure of root tissues appeared significantly modified by Ag treatment even though the different cell compartments were still recognizable. The main changes concerned the cortical parenchymal cells where the plasmalemma was often detached from the cell wall (Figure 1A,

click here arrowheads). Unlike the roots, numerous electron-dense Ag particles of different sizes, often forming consistent aggregates, appeared in the shoots in association with different cell compartments (Figure 2) such as cell walls (Figure 2A,B, arrows), chloroplasts (Chl in Figure 2B, arrows), see more plasmalemma and cytoplasm (Cyt in Figure 2C,D, arrows). In the xylem, Ag precipitates were distributed along the cell wall and, to a lesser extent, in the cell lumen (not shown). Ag treatment led to severe consequences in the stem tissues of the three plant species. In fact, the parenchymal cells of the stem showed anomalous shapes (Figure 2A). Cells had the appearance of being plasmolyzed, and the consequent condensation of the cytoplasm (Cyt in Figure 2C,D) made recognition of the organelles

difficult. The chloroplasts were altered by disorganization of the lamellae (Chl in Figure 2B) PRKACG and by anomalous formation of starch granules (Str in Figure 2B). In leaf tissues, Ag-like precipitates with different shapes and sizes (Figure 3A, arrows) were observed in association with the cell wall (W NF-��B inhibitor in Figure 3A) as well as the cytoplasm (Cyt in Figure 3B, arrows) and chloroplasts (Chl in Figure 3C, arrows). Electron-dense particles had also accumulated along the plasmalemma (Figure 3D,E, arrows). Similar to the observations in stems, precipitates were also present in the cell walls of the xylem elements (Xyl in Figure 3D,E, arrows). Precipitates were never observed in the phloem of the three plant species. As observed in the stems, Ag treatment also caused severe modifications

to the cell structures in the leaf tissues. Parenchymal cells also seemed to have been plasmolyzed with an associated cytoplasmic condensation (Cyt in Figure 3B,E), chloroplasts contained large starch granules (Str in Figure 3C), and the walls were distorted (Figure 3D, arrowheads). X-ray microanalyses and Ag-like particle identification X-ray microanalysis was performed on the electron-dense Ag-like particles observed in the different tissues of the three plant species. Some representative images of electron-dense precipitates recovered from the roots of F. rubra are shown in Figure 4 and those from the leaves of M. sativa and B. juncea in Figures 5 and 6, respectively. The X-ray spectra of elements recovered in Ag peaks, at 23 keV, were clearly visible.