MAX2 controls the basal level of stomatal conductance. Effects of 3 h 350 nmol/mol O3 exposure on stomatal conductance were measured on wild-type Col-0 and max2 mutants with a custom made whole-rosette gas exchange measurement device. A) Stomatal conductance before, during and after 3 h O3 exposure of Col-0 and max2 plants. B) CO2 uptake rate of max2 mutants and Col-0 before, during and after 3 h O3 exposure. C) Cumulative dose of O3 absorbed by max2 and Col-0 plants before, during and after 3 h O3 exposure. D) Stomatal O3 uptake rate of max2 mutants and Col-0. For each line 4 plants were used in the experiment and the results are shown as means ± SE. Experiments were repeated twice with similar results.