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The Effect of Tentoxin on Stomatal Aperture and Potassium Content of Guard Cells. R. D. Durbin, Research Leader, U.S. Department of Agriculture and Department of Plant Pathology, University of Wisconsin, Madison 53706; T. F. Uchytil(2), and L. Sparapano(3). (2)(3)Professor, Research Assistant, and C.N.R. Fellow (Italy), respectively, U.S. Department of Agriculture and Department of Plant Pathology, University of Wisconsin, Madison 53706. Phytopathology 63:1077-1078. DOI: 10.1094/Phyto-63-1077.

Tentoxin induced closure of stomata on broad bean leaflets and epidermal strips kept in light. The extent of closure in leaflets was directly correlated with tentoxin concentrations between 100-10 µM. The toxin also retarded stomatal opening in the dark when CO₂ concentration was reduced. The uptake of potassium by guard cells was inhibited in the presence of tentoxin.