Fig. 2.

Changes in (A) leaf net assimilation rate (A), (B) stomatal conductance to water vapour (g_s), and (C) intercellular CO₂ concentration (C_i) of mature leaves of 10-12 weeks old N. tabacum ‘Wisconsin’ in relation to ozone concentration during exposure. The measurements were taken at 0.5 h after ozone exposure at 0, 400, 600, 800, and 1000 ppb for 30 min in a custom-made cylindrical double-walled glass chamber 25 °C. All measurements were replicated at least thrice. Gas exchange measurements were conducted at leaf temperature of 25 °C, quantum flux density of 700 μmol m^-2 s^-1 at leaf surface, ambient CO₂ concentration of 380-400 μmol mol^-1, and relative air humidity of 50–60%. Each data point corresponds to an individual replicate measurement. Data were fitted by Spearman correlations. Statistical significance of regressions is indicated as: *** -P < 0.001.