Abstract
Inoue, H. and Katoh, Y. 1987. Calcium inhibitsion-stimulated stomatal opening in epidermal strips of Commelina communis L.—J. exp. Bot. 38: 142–149. Ca2+ suppressed both the ion-stimulated stomatal opening and H+ extrusion of pre-illuminated epidermal strips isolated from Commelina communis L. In the absence of Ca2+, the rate of H+ release was 18 nmol H+ cm–2 h–1 per epidermal strip unit area in 150 mol m–3 KCL at pH 7·4. Half-maximum inhibition of stomatal opening was observed with 220 mmol m–3 of Ca2+. The hexavalent dye, ruthenium red, showed concentration-dependent prevention of the inhibition by Ca2+ of the ion-stimulated stomatal opening. The effect of ruthenium red was non-competitive, and the K1 for the calcium inhibition was found to be 3·6 mmol m–3. The calcium inhibition of H+ extrusion was also prevented by ruthenium red. These results suggest that Ca2+ inhibits the activity of electrogenic H+ translocating ATPase of the guard cell plasma membrane and leads to the suppression of stomatal opening.
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