Pathogen-triggered stomatal closure is impaired in max2 mutant lines. Four-week old wild-type Col-0 and max2 lines were inoculated with Pseudomonas syringae pv. tomato DC3000. A) Measurement of stomatal aperture of wild-type Col-0 and max2 lines in response to P. syringae. Leaves were first stained with 20 μM propidium iodide (PI) solution and then inoculated with 300 μl of bacterial solution (108 cfu/ml). Stomatal aperture width was measured after indicated time points using ImageJ image processing program. B) Representative pictures of stomatal response of Col-0 and max2 lines under florescent microscope using 20x objective 0, 1, 2 and 4 h after inoculation with the bacteria. Results are shown as the mean (n = 80-100) ± SE. **P < 0.01; two-tailed t test. The experiments were repeated three times with similar results.