FIGURE 1.

Salmonella enterica serovar Typhimurium (STm) mutant screening analysis. (A) STm 14028s and STm SL1344 induce similar stomatal reactions in lettuce leaves at 2 and 4 h post-inoculation (hpi). Leaf sections were floated on bacterial suspensions (1 × 10⁸ CFU/mL). Results are shown as the mean (n = 20) ± standard error (SE) calculated from two independent leaves. Different letters above the bars indicate statistically significant differences among the means (ANOVA with post hoc Tukey HSD test; p < 0.05). (B) Circadian rhythm of stomatal movement on non-inoculated lettuce leaves. Mean stomatal aperture widths (n = 80 ± SE) of eight biological replicates (i.e., four different leaves and the experiment performed twice). Ten stomata were imaged per leaf. Different letters above the bars indicate statistically significant differences among the means (ANOVA with post hoc Tukey HSD test; p < 0.05). (C) Stomatal response to selected bacterial mutants. Lettuce leaf sections were floated on bacterial inoculum (1 × 10⁸ CFU/mL) and stomatal aperture widths were measured at 4 hpi. Results are shown as mean stomatal aperture width (n = 120; 40/biological replicate) from three independent leaves and SE. Statistical difference between the means (STm 14028s vs. mutant) was determined using Student’s t-test (**p < 0.01).