Step 1: Picture a growing pollen tube from tip to base. At the very tip is a clear, vesicle-rich apical zone that drives extension growth.
Step 2: Just behind this sits the nuclear zone, which carries the vegetative nucleus along with the generative cell or the two sperm cells it has already produced.
Further back, the tube develops a large central vacuole, marking the vacuolated zone, and older parts get sealed off by callose plugs.
A meristematic zone, meaning a region of active cell division, is never part of this pattern because pollen tube elongation is tip growth, not cell division.
