Fig. 3. Relationships between relative value of ΦPSII and A during desiccation of detached leaves from P. vulgaris. The O2 molar fraction during measurements was either 21 % (closed circles) or 1 % (open circles) in nitrogen. Other conditions were as follows: leaf temperature, 23·5 °C initially, increasing to 24·9 °C at the end of the measurements; PFD, 450 µmol m–2 s–1; and Ca, about 360 ppm. Relative water content of the leaves at the end of the experiments was 76·2 and 72·8 % in 21 and 1 % O2, respectively (G. Cornic, unpubl. res.).