Fig. 11. Movement of FM4-64-stained material in the apex of a L. longiflorum pollen tube (average growth rate 21.9 µm/minute). (A-C) Median section confocal images taken 2 seconds apart showing bulk movement of FM4-64-stained material from a region 5 µm behind the apex away from the tip along the path of cytoplasmic streaming (arrows). (D-I) Images from the same time series, taken 1 second apart, showing movement of FM4-64-stained material from a region 25 µm subapically back towards the apex (arrows). Diagrammatic interpretation of the `reverse fountain' path of cytoplasmic streaming in a growing L. longiflorum pollen tube (J) (see main text), and of the movement of FM4-64-stained material based upon time-sequence imaging (see A-I) and FRAP experiments (see text for details) (K). Bar, 20 µm.