Fig. 2. Relationship between A_max, the net photosynthesis (net CO₂ or net O₂ evolution) measured at elevated C_a (up to 10 %) and A, the net CO₂ uptake by leaves maintained at normal C_a. Both A_max and A were measured during a drought. A is taken as an indicator of the water status in the leaf: it decreases as desiccation increases. Data are taken from Cornic et al. (1989, Figs 1 and 2A), Graan and Boyer (1990, Fig. 5A) and Tourneux and Peltier (1995, Figs 4C and 5).