Redox state of the PQ pool and chlorophyll a fluorescence emission of Synechocystis sp. strain PCC 6803 cells under various illumination conditions. A, PQ redox states. Samples were taken after 30 min in the dark, after 10 min in 100 µmol photons m−2 s−1 625-nm light, and 10 min after the addition of 25 µmol photons m−2 s−1 730-nm light. Black bars, BG-11 medium with 0.5 mm NaHCO3; gray bars, BG-11 with 50 mm NaHCO3. Data shown are averages of biological duplicates with sd. B, Chlorophyll a fluorescence recordings. Striped bar, 100 µmol photons m−2 s−1 625-nm light; dotted bar, 100 µmol photons m−2 s−1 625-nm light with 25 µmol photons m−2 s−1 730-nm light; black bar, dark; dashed lines, F0 and Fm. AU, Arbitrary units.