Fig. 3.

Relationship between the inverse of chloroplastsurface area exposed to intercellular airspace per unit leaf area (S _c/S)^–1, and the sum of individual cellular resistances [(r _cw+r _pl+r _cyt+r _env+r _str)]. Both axes are log-transformed. Log (liquid-phase resistance) is the sum of these two log-components, Log[(S _c/S)^–1] and Log(r _cw+r _pl+r _cyt+r _env+r _str) and increasestowards the upper right corner. The sum of serial liquid-phase resistances was calculated assuming a constant mesophyllcell wall porosity of 0.05 for all species (a), or assumingvariable porosity of mesophyll cell walls, with porosity rangingfrom 0.040 to 0.095, decreasing with increasing depth of cellwall (b). A constant value of 0.0035 m s^–1 was assigned toboth r _pl and r _env. Symbols and error bars as in Fig. 1.