Fig. 6. As for Fig. 5 but O₂ evolution was measured only at 1 % CO₂. Sunflower leaf discs were intact (closed circles) or peeled and lacking the abaxial epidermis (open circles). Also shown are data from Fig. 3 (intact, closed triangles; peeled, open triangles). The individual measurements were pooled from five repeated experiments with plants grown and dehydrated in a glasshouse or growth chamber before the discs were sampled and peeled. Other conditions for O₂ evolution were as described in Fig. 5.