Figure 2.

Rate of O₂ evolution during steady-state photosynthesis in relation to external Ci in Synechococcus sp. strain PCC7002. ○, Cells grown continuously on 20 μL of CO₂ L⁻¹ (low-Ci cells); □, cells grown continuously on 2% CO₂ (high-Ci cells); •, high-Ci cells subjected to the fast-induction protocol for 10 min in the presence of CA; ▪, high-Ci cells subjected to the fast-induction protocol for 10 min in the absence of CA; ▴, high-Ci cells subjected to the fast-induction protocol for 10 min in the presence of CA and 50 μm AZA; ♦, high-Ci cells that were not fast induced but tested in the presence of CA. Fast-induced cells were obtained in experiments similar to those shown in Figure 1. After the 10-min illumination period (750 μmol photons m⁻² s⁻¹) an aliquot of the cells containing 10 μg of Chl was centrifuged and resuspended in 4 mL of assay buffer to a final [Chl] of 2.5 μg mL⁻¹. To fully inhibit CA activity, 50 μm AZA was added and the Ci-dependent O₂ evolution was followed.