Fig. 4.

The response of CO₂ assimilation (a) and PSII operating efficiency (b), estimated from F _q′/F _m′, to changes in internal CO₂ concentration (C _i) under 20 mmol mol^–1 O₂ and at 200 (open circles), 500 (grey circles), and 800 (filled circles) µmol m^–2 s^–1 PPFD. The correlation between CO₂ assimilation and PSII operating efficiency (c) was fitted using a linear regression for each PPFD intensity. All measurements were made on 5-week-old A. thaliana. Air temperature and VPD were 25 °C and 1.2 kPa, respectively. Data are the means with standard errors (n=3–5).