DYNAMIC ORGANIZATION OF MICROTUBULES IN GUARD-CELLS OF VICIA-FABA L. WITH DIURNAL CYCLE

Stomatal movement is regulated by changes in the volume of guard cells , thought to be mainly controlled by an osmo-regulatory system, In the present study, we examined the additional involvement of cytoskeletal events in the regulation of stomatal movement, Microtubules (MTs) in guard cells of Vicia faba L., grown under sunlight, were observed duri ng the day and night by immunofluorescence microscopy, Cortical MTs be gan to be organized in a radial array at dawn and increased in numbers in the morning following the increase in the stomatal aperture size, Thereafter, MTs became localized near the nucleus and began to be dest royed from the evening to midnight, following the decrease in stomatal aperture size, These diurnal changes in MT organization were observed even two days after transfer from natural light condition to total da rkness, and were accompanied by corresponding changes in stomatal aper ture, The increase in stomatal aperture sine in the early morning was inhibited by 50 mu M propyzamide, which destroys cortical MTs in guard cells, whereas the decrease in aperture size in the evening was suppr essed by 10 mu M taxol, which stabilizes cortical MTs, These results s uggest that radially-organized cortical MTs of guard cells may control diurnal stomatal movement.