Dark-adapted (10 min darkening) average (±SE) maximum fluorescence yield of photosystem II (PSII; Fv/Fm) of mature leaves of 10-12 weeks old Nicotiana tabacum ‘Wisconsin’ at 0.5, 3, 10, 24, and 48 hours of recovery following the exposure with ozone concentrations of 0, 400, 600, 800, and 1000 ppb for 30 min in a custom-made cylindrical double-walled glass chamber at 25 °C. All measurements were replicated at least thrice.