Figure 3.

H₂O₂ Induces Stomatal Opening at Low Concentrations.

(A) H₂O₂ promotes stomatal opening at low concentrations. The rosette leaves of 4-week-old Col-0 were transferred to half strength MS liquid medium, incubated overnight in the dark, and then added to different concentrations of H₂O₂ and incubated for 3 h in darkness. The leaves were then harvested, and stomatal apertures were measured.

(B) to (D) Quantification of stomatal apertures ([B] and [C]) and starch granules (D) in guard cells of intact leaves of the wild type and different mutants with or without H₂O₂ and BR treatment. The rosette leaves of the 4-week-old wild-type Col-0, bzr1-cr1, and bes1-cr1 plants were transferred to half strength MS liquid medium and incubated overnight in the dark. Next, 30 µM H₂O₂, 100 nM BL, or 80% ethanol solution was added to the medium at the EoN and illuminated with white light for 3 h.

The ratio of stomatal aperture width to length or guard cell starch granules from 100 cells of 15 leaves of eight different plants were measured using ImageJ software. Three independent biological repeats were performed. Error bars indicate sd (n = 3 biological repeats). Different letters above the bars indicate statistically significant differences between the samples (two-way ANOVA, [B] and [C], or one-way ANOVA [D] followed by a post hoc Tukey test, P < 0.05).