Fig. 2.

C₄-optimized PEPC levels. (a) Optimal PEPC concentration as a function of the core radius, r_i, and the periphery to core distance, r_v–r_i, for a cell at 20 °C with Rubisco concentration of c_R=2 mM and cellular barrier permeability of σ_B=100 μm. Other parameters are as in Table 1. Level lines are in white. The abundant PEPC region, which appears white, has PEPC concentration >1 mM; the black region on the left is the C₃ region, with zero PEPC concentration. (b) Dependence of the photon cost on PEPC concentration, c_P, at three exemplary points in different regions of (a), with co-ordinates r_i=5.5 μm, 10.5 μm, and 12.6 μm, and r_v–r_i=26 μm. Arrows mark the positions of the photon cost minima (i.e. the optimal PEPC concentrations) in the three cases (discussed in the text).