Cytoskeletal inhibitors suppress the stomatal opening of Vicia faba L. induced by fusicoccin and IAA

Stomatal movement is governed by osmotic potential, in which K+ concentrati on plays the dominant role. Our previous work has shown that both microtubu les and microfilaments are involved in regulating stomatal movement. In the present investigation the relationships between cytoskeletal components an d K+ fluxes in stomatal opening were addressed by using fusicoccin (FC), in doleacetic acid (IAA), and cytoskeletal inhibitors to treat both epidermal strips and protoplasts of guard cells. The results revealed that FC and IAA induced stomatal opening with or without KCI in the dark. Also FC or IAA i nduced guard cell protoplast swelling in the dark even without added KCI. H owever, the induction was partially suppressed when strips and protoplasts were pretreated with cytochalasin B (CB), an inhibitor of F-actin polymeriz ation, or oryzalin, an inhibitor of plant microtubule polymerization. Thus our preliminary results indicate for the first time that microtubules and m icrofilaments can affect stomatal opening independently of K+ fluxes. (C) 2 000 Published by Elsevier Science Ireland Ltd. All rights reserved.