Figure 2.

Stomatal performance of wild-type and KAT1∷En-1 plants. (A) Light-induced stomatal opening from wild-type (open bars) and KAT1∷En-1 (filled bars) plants. Stomatal apertures were measured after a 3-h illumination period of epidermal peels incubated in concentrations of KCl as indicated. Mean values (± standard errors) are shown. (B) Stomatal movement in wild-type and KAT1∷En-1 leaves in response to CO₂ and ABA. Leaves from predarkened plants were placed in a gas exchange chamber and superfused continuously with CO₂-free air for stomatal opening. Application of either 340 ppm of CO₂ or 100 μM ABA (arrows) induced stomatal closure, whereas removal of CO₂ led to reopening of stomata (arrows). Transpiration rates are given in arbitrary units. Bars represent 20 min and 0.5 mmol m⁻² per s, respectively. (C) Apoplastic changes in K⁺ activity (pK) during light-dependent stomatal opening of representative wild-type and KAT1∷En-1 plants. Following the dark-conditioning characterized by stable K⁺-activities the application of continuous white light (200 μmol m⁻² per s) caused a decrease in the K⁺ activity (increase in pK) reaching a stable value after ≈20 min.