Fig. 2. Detection of intracellular NO in a growing pollen tube of lily using the NO-specific fluophore DAF2-DA (1'). Fluorescence is seen in the cytosol, with less intensity in the apical domain, and is very bright on round cytoplasmic organelles. The spatiotemporal dynamics of intracellular NO is shown in the form of kymographs in which we averaged an active representative region inside each pollen tube at each time-point as a color-coded line (see top wedge), and plotted these lines as a function of time (y-axis) and pollen tube length (x-axis). For the sake of clarity, the pollen tube tip was aligned with the right side, and therefore the slope on the left side of the kymograph reflects the growth rate. The chronological order of each time point is read from top to bottom as illustrated by the arrow on the y-axis. In a non-challenged pollen tube (control), no significant variation along time is seen. Apical depletion and subapical accumulation of NO are clearly visible. Incubation with the NO-scavenger CPTIO (44') almost suppressed the signal from the cytosol, but the round organelles are still distinguishable. Kymograph analysis shows the overall decrease after CPTIO addition, but the apical/subapical pattern, polarity and dimensions are maintained.