Disruption of Microtubules by Abscisic Acid in Guard Cells of Vicia faba L.

ABA disrupted cortical microtubules in guard cells, but not in epidermal cells, with concomitant closure of stomata. Other plant growth regulators did not disrupt the microtubles in guard cells. Thus disrution of microtubules seems to be a specific effect of ABA in guard cells but its physiological significance remains obscure.