Figure 2.

Typical variation of the FM4–64 fluorescent signal in a growing pollen tube. Since FM signal is a combination of new internalysed dye and movement of previously stained vesicles, fluorescence intensity (FI) was represented as the ratio apical/sub-apical signal (measured respectively in the first 10 µm and 10–20 µm of an individual A. umbellatus pollen tube apex). Equivalent data were obtained in 8 independent experiments. Associated to changes in the growth axis (indicated by vertical dashed lines), one can observe rapid decreases (“collapse event”) of apical/sub-apical FM signal followed by slower recovery periods where growth is approximately straight.