Figure 4.

Various strategies to increase mesophyll surface areas. A, Cell elongation. B, Cell elongation accompanied by cell division. C, Decrease in cell size. D, Armed cells of grass species having lobes. For cells having the same cell walls of equal thickness, the tissue with smaller cells is mechanically tougher (Terashima et al., 2001). The leaves with larger cells would expand faster. On the other hand, these would inevitably be thicker to have enough S_mes to accommodate chloroplasts, in which case the diffusion in the intercellular spaces becomes significant. Such leaves, mostly in annual herbs, tend to have stomata on both epidermises (Terashima et al., 2006). The acclimation of photosynthetic properties of chloroplasts to the local light environment may be more precise in cells in B than in those in A. In grass leaves, armed cells have large cell surface areas. In rice, almost all the cell surfaces facing the intercellular spaces are occupied by chloroplasts. Mitochondria are located in the capsule made by chloroplasts. For more insightful discussion for grass leaves, see Sage and Sage (2009).