Abstract: | Inoue, H. and Katoh, Y. 1987. Calcium inhibitsion-stimulatedstomatal opening in epidermal strips of Commelina communis L.J.exp. Bot. 38: 142149. Ca2+ suppressed both the ion-stimulated stomatal opening andH+ extrusion of pre-illuminated epidermal strips isolated fromCommelina communis L. In the absence of Ca2+, the rate of H+release was 18 nmol H+ cm2 h1 per epidermal stripunit area in 150 mol m3 KCL at pH 7?4. Half-maximum inhibitionof stomatal opening was observed with 220 mmol m3 ofCa2+. The hexavalent dye, ruthenium red, showed concentration-dependentprevention of the inhibition by Ca2+ of the ion-stimulated stomatalopening. The effect of ruthenium red was non-competitive, andthe K1 for the calcium inhibition was found to be 3?6 mmol m3.The calcium inhibition of H+ extrusion was also prevented byruthenium red. These results suggest that Ca2+ inhibits theactivity of electrogenic H+ translocating ATPase of the guardcell plasma membrane and leads to the suppression of stomatalopening. Key words: Calcium, Commelina communis, ruthenium red, stomata |