Fig. 4. Relationship between A and the leaf internal CO2 molar ratio (Ci) measured on detached Lavatera trimestris L. leaves either before (well‐hydrated, closed circles) or after (open circles) a rapid desiccation. Plants were grown in winter, in a peat soil, in a temperature‐controlled glasshouse in the University of Illinois at Urbana‐Champaign, USA (temperature from about 20 °C during the day to 17 °C during the night). Measurements were made with a LICOR 6400 under either a PFD of 450 (A) or 990 (B) µmol m–2 s–1. Other conditions were as follows: leaf temperature 25 ± 0·3 °C; Ca, 350 ppm; and VPD, 1·5 ± 0·5 kPa. Relative water content of the leaves at the end of the experiments was 70·4 and 67·7 % for A and B, respectively (G. Cornic and S. Long, unpubl. res.).