Figure 5.

The animal purinergic receptor antagonist PPADS blocks ATPγS-induced changes in stomatal aperture and partially blocks the effects of ABA and light on stomatal aperture. A, Treatment with 200 μm ATPγS induced stomatal closure in leaves and cotreatment with 100 μm PPADS blocked this closure, but 100 μm PPADS alone had no effect on stomatal aperture. Treatment with 10 μm ABA induced stomatal closure and cotreatment with 100 μm PPADS partially blocked this ABA-induced stomatal closing (4.9 μm average width for control). B, Treatment with 15 μm ATPγS induced stomatal opening in epidermal peels and cotreatment with 100 μm PPADS blocked this opening, but 100 μm PPADS alone had no effect on stomatal aperture. Treatment with light induced stomatal opening, although cotreatment with 100 μm PPADS partially blocked this light-induced stomatal opening (1.7 μm average width for control). Apertures were measured as width/length after 1 h of treatment for peels and after 2 h of treatment for leaves. 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.