Fig. 6: Carbon dioxide acquisition efficiencies and photorespiration rates of the diatom Thalassiosira weissflogii grown under varying levels of pCO₂ and pO₂.

Net photosynthesis vs CO₂ concentration curves was compared under standard conditions (pH_T = 8.00, light of 400 μmol photons m⁻² s⁻¹, and DO of 50–200 μM) for cells grown under (a) ambient CO₂ (AC, circles, ~15 μM) and (b) high CO₂ (HC, triangles, ~35 μM) at ambient (AO, black symbols, ~255 μM) and low O₂ levels (LO, red symbols, ~57 μM). Insets present CO₂ acquisition efficiencies (V_max/K_0.5 for CO₂). (c) Photorespiration of cells under the growth pCO₂ and pO₂ levels. (d) The correlation between photorespiration and CO₂ acquisition efficiency (P = 0.0023, r = −0.7886, Pearson correlation analysis, two-tailed). The values represent means (a–c) or all replicate data (d), and error bars indicate the standard deviations of independent biological replicates (n  =  3). Light-colored symbols are individual data corresponding to the treatments. Different letters above the bars represent significant differences (P < 0.05, LSD test) among the treatments. The detailed information for the experimental features and timing points for the above determinations are shown in Supplementary Fig. 3.