Figure 1. (A) Treatment with light induces stomatal opening. Treatment with 15 μM ATPγS or 1.5 μg/mL apyrase inhibitor NGXT191 or 1.5 μg/mL apyrase inhibitor #13 induces stomatal opening in the dark. (B) Treatment with 100 μM DTT blocks light-induced opening. (C) Treatment with light and treatment with 150 μM ADP in the dark induces stomatal opening in Col-0 and the gpa1–3 mutant. Apertures measured in epidermal peels as width/length after 2 h treatment of whole leaves. Different letters above bars = mean values that are significantly different from one another as determined by Student’s t-test (p < 0.05; n > 50).