Figure 2.

cax1, cax3, and cax1/cax3 mutants are impaired in light-induced stomatal opening. A, Stomatal response to ABA is normal in cax1, cax3, and cax1/cax3. Epidermal strips were incubated 2 h in an opening buffer, and treated with 0, 1, and 5 µM ABA for 1 h prior to measurements of stomatal apertures. Data are mean ± sem (n = three independent experiments, >90 stomata for each data point). B, Light-induced stomatal opening is impaired in cax1, cax3, and cax1/cax3 compared with wild-type plants. Data are mean ± sem (n = five independent experiments, >100 stomata for each data point). C, cax1/cax3 guard cells have depolarized membrane potential compared with that of the wild type. Membrane potential was measured using the fluorescence dye DiBAC₄ in the wild type and cax1/cax3. Higher fluorescence indicates depolarization of the plasma membrane. Average fluorescence from 685 (the wild type) and 917 (cax1/cax3) stomatal complexes is presented. Error bars = se.