Fig 8. Altering chloroplast surface coverage and light harvesting capacity.
(a) The assimilation rate per cell surface area as a function of chloroplast surface coverage in the case of C3 photosynthesis (black line) and C4 photosynthesis at the C4 cycle activity levels where light-use reaches 40 mol m-3s-1 and 80 mol m-3s-1 thresholds (red lines). The numbers in parentheses show the respective photon costs (black), PEPC-vs-RubisCO carboxylation capacity ratios (blue), and the fraction of current through PS-I due to cyclic electron transfer (red). Green arrows illustrate organism modification strategies discussed in the main text. Parameters as in Fig 4. (b) An outline of a recipe for making a functional C4 photosynthesising prototype. (c) and (d): The photon cost and assimilation rate as functions of the surface coverage and threshold light-use in C4 photosynthesis. The panels are a remapping of Fig 4 with an alternate y-axis. Level-lines are in white. In the dark region at the bottom the light-use is below the requirements of C3 photosynthesis. The top right dark region corresponds to PEPC levels beyond those simulated. The green circles and arrows mark the modification strategies shown in (a).