Figure 1.

Response of net CO₂ assimilation rate, A, to increasing ambient CO₂ concentration, C_a, for sunflower leaves, with (•) and without (○) parts of the leaf being covered with grease. The right-hand axis (▵) indicates the ratio of A in covered (A^c) and not-covered (A) leaves. A, One-half of the total leaf area covered (both surfaces; •); B, the whole of the lower surface of the leaf covered (•); C, one-half of the leaf covered in 4-mm-diameter grease patches (both surfaces; •). Conditions: PPFD = 1,000 μmol m⁻² s⁻¹; leaf temperature = 25°C; water vapor in the leaf chamber approximately 15 mmol mol⁻¹; O₂ = 21%.