Fig. 1. FM4-64 staining distribution in a growing pollen tube of L. longiflorum. (A) Typical median focal plane confocal optical section; the bright field image at 1/3 size appears as an insert. (B) Pixel values along a central transect through the fluorescence image in (A). (C) Representative diagram of FM4-64 staining in the L. longiflorum pollen tube apex. The apical V-shaped `clear zone' of secretory vesicles defined previously (Lancelle and Hepler, 1992) on the basis of electron microscopy analysis is shown in relation to the different `zones' defined by the FM4-64 signal (see text).