Fig. 1
Net photosynthesis (a) and stomatal conductance (b) of treated (dark grey) and control (light grey) leaves of Q. ilex, measured before the start of the first ozone fumigation and at 5, 8, 12 and 14 days after. Days in which fumigation occurred are indicated with arrows; error bars represent standard error of the means. Different letters indicate significant differences (P < 0.001) between the treatments