Figure 5.

Transects of intercellular CO₂ concentration, C_i, across a 4-mm-diameter grease patch applied to part of a leaf of P. vulgaris. Symbols indicate the mean C_i values calculated from the F_q′/F_m′ images shown in Figure 4 for three rows of 0.15-×0.15-mm pixels on a horizontal transect. Lines show the C_i values estimated from a model of lateral CO₂ diffusion (see text for details). The fitted CO₂ diffusion coefficient reduction factors , φ, for the curves in A were 9.4% (lower) and 10.8% (upper), and in B were 15.8% (lower) and 8.5% (upper). C_i values shown are those for the unpatched leaf area. For the highest C_a, C_i values above 400 μmol mol⁻¹ could not be reliably estimated from F_q′/F_m′. Dotted vertical lines indicate the position of the patch.