Figure 4.

Dose-response curves for the effects of various concentrations of ATPγS on stomatal aperture in epidermal peel experiments. A, Treatment with 10 μm ABA induced stomatal closure in the light, as did 200 and 250 μm ATPγS. Treatment with 150 μm ATPγS or 250 μm AMPS had no statistically significant effect on stomatal aperture (6.3 μm average width for control). B, Treatment with 1 h of light induced stomatal opening, and application of 5 and 15 μm ATPγS induced stomatal opening in darkness. Treatment with 15 μm AMPS had no effect on stomatal aperture (2.1 μm average width for control). Apertures were measured as width/length after 1 h of treatment. Error bars represent se. Different letters above the bars indicate mean values that are significantly different from one another as determined by Student’s t test (P < 0.05; n ≥ 50). These data are representative of three or more biological repeats.