Figure 4.

Stomatal closure of wild-type (WT), atpub18-2atpub19-3 and atpub22atpub23 mutant, and 35S:AtPUB18-, 35S:AtPUB19-, 35S:AtPUB22-, and 35S:AtPUB23-overexpressing transgenic plants in response to H₂O₂, CaCl₂, and mannitol. Mature leaves, pretreated with stomatal opening solution, were transferred to solutions containing various concentrations of H₂O₂ (A), CaCl₂ (B), or mannitol (C), each for 2 h. Epidermal peels were mounted on microscope slides, and stomata were observed with bright-field microscopy. Stomatal apertures were measured with three replicates. Error bars represent sd (n > 87; *P < 0.05, **P < 0.005, Student’s t test). Bars = 10 µm. [See online article for color version of this figure.]