Effect of ouabain on stomatal movements and transpiration rate of Secale cereale

Young rye seedlings (Secale cereale cv. Petkus) were grown for 12 or 18 din aerated nutrient solution. CO2-free air in light or in darkness induced stomatal opening. When light and CO2-free air were applied together, maximum stomatal opening was observed. Na+ channel inhibitor 3H]ouabain was taken up from nutrient medium and translocated into the leaves via the xylem sap. The presence of 10-5 M ouabain in the root medium for 20 h increased stomatal opening and transpiration rate. On the other hand, stomatal closing was not affected by the presence of ouabain. These results suggested that Na+ might play a role in stomatal movements. This revised version was published online in July 2006 with corrections to the Cover Date.