Pollen germination and pollen tube growth were clearly affected by the drug brefeldin A: both processes could be stopped completely. Notable thickening of the cell wall was not observed in non-growing pollen tubes, and plasma streaming remained vigorous in the presence of brefeldin A. Over time, the tip region became filled with a dense cytoplasm that lacked large organelles. Ultrastructural observation showed the rapid dissociation and disappearance of Golgi bodies. The concomitant appearance of vesicle-like structures attached to the endoplasmic reticulum (ER) suggests a fusion of the Golgi with the ER similar to that which happens in animal cells. Secretory vesicles disappeared from drug-treated tubes, and the tip region became filled with tubular ER. As the actions of the drug seemed to be reversible, brefeldin A may contribute substantially to research on Golgi dynamics and tip growth in pollen tubes.