CO2-fixation Sites in Leaves of Maize and Oats

The primary site of photosynthetic carbon dioxide fixation wasdetermined in the leaves of two monocot species by means ofmicroautoradiographic techniques. Carbon fixation occurred primarilyin the vascular-bundle sheath cells in maize whereas fixationin oat occurred uniformly throughout the leaf. The evidencepresented suggests that the bundle sheath cells of maize fixcarbon via the C.4 dicarboxylic acid pathway.