Figure 6.

Characteristics describing high-VPD-induced stomatal closure and low-VPD-induced stomatal opening. A, Stomatal closure and opening half-response times indicate the times when half of the measured VPD response was completed. B, High-VPD-induced stomatal closures and low-VPD-induced openings within the initial 40 min of VPD change (gs₄₀ − gs₀). Percentages show the values of gs after 40 min under the respective VPD treatment, expressed as a ratio of the initial pretreatment value (in percentage). C, Initial closure and opening rates calculated by fitting a second-order polynomial on the time series of gs values after the change in VPD. Significant differences are denoted with different letters in Arabidopsis and with asterisks in tomato (ANOVA and Tukey’s posthoc test). In pea, no significant differences between wilty and the wild type (wt) were detected. D, Relationship between leaf ABA level and the ratio of closure to opening half-response times in Arabidopsis ABA-deficient mutants and Col-0.