SEARCH Articles Figures Tables A simplified cross-section in a leaf indicating the CO2 diffusion pathway between the atmosphere and the chloroplast. Changes in CO2 concentrations and the and values along this pathway are indicated for the atmosphere, c, the leaf boundary layer, Cb, substomatal internal air spaces, Cj, the chloroplast surface, Ci and the center of the chloroplast, c, are indicated . The difference between the two one-way fluxes constitutes CO2 assimilation into sugars values for [Publishers Imprint]