Fig. 4

Light micrographs of serial radial sections a without staining and b after staining with toluidine blue, c with iodine–potassium iodide and d with amido black in the previous year’s xylem, showing the contents of ray parenchyma cells. White arrows indicate nuclei. Black arrows indicate starch grains. Yellow arrowheads indicate lipid droplets stained by osmium tetroxide. Black arrowheads indicate protein storage vacuoles (PSVs) stained by osmium tetroxide, toluidine blue and amido black. White arrowheads indicate non-PSVs that were unstained by these stains. Bars 10 μm