Abstract: Turgor pressure induced by osmotic substances, such as K + , C1-, and malate, stimulates the stomatal movements. Microtubules (MTs) and microfilaments (MFs) may be involved in regulating the stomatal movements. Abscisic acid-induced changes in the orientation of cortical MTs in stomatal movement of Vicia faba L. were observed with electron microscopy. It was shown that the MTs in the open stomata stimulated by light were oriented in a position transverse to the ventral wall in paradennal sections and parallel to the outer wall in cross sections (MTs were paradermally sectioned). MTs in the closed stomata induced by darkness were parallel to the dorsal and the ventral walls in paradennal sections (MTs were transversely sectioned) and transverse to the outer wall in cross sections (MTs were paradermally sectioned). However, MTs in the closed stomata induced by ABA in the light were oriented both transversely (MTs were paradermally sectioned) and parallelly (MTs were paradermally sectioned) to the ventral wall in paradermal sections. The results indicate that the changes of MT orientation induced by ABA are associated with the stomatal movement.

Key words: Vicia faba, Stomata, Abscisic acid, Microtubule