Microtubule dynamics are involved in stomatal movement of Vicia faba L.

To obtain a full picture of microtubule (MT) behavior during the opening and closure of guard cells we have microinjected living guard cells of Vicia faba with fluorescent tubulin, examined fine detail by freeze shattering fixed cells, and used drug treatments to confirm aspects of MT dynamics. Cortical MTs in fully opened guard cells are transversely oriented from the ventral wall to the dorsal wall. When the stomatal aperture was decreased by darkness, these MTs became twisted and patched and broken down into diffuse fragments when stomata were closed. When the closed stomata were opened in response to light, the MTs in guard cells changed from the diffused, transitional pattern back to one in which MTs are transversely oriented from stomatal pore to dorsal wall. This observation indicates a linkage between these MT changes and stomatal movement. To confirm this, we used the MT-stabilizing agent taxol and the MT-depolymerizing herbicide oryzalin and observed their effects on the stomatal aperture and MT dynamics. Both drugs suppressed light-induced stomatal opening and dark-induced closure. MTs are known to be necessary for maintaining the static kidney shape of guard cells; the present data now show that the dynamic properties of polymeric tubulin accompany changes in shape with stomatal movement and may be functionally involved in stomatal movement.