Is photosynthesis during the induction period in maize limited by the availability of intercellular carbon dioxide?

Whether stomatal conductance may limit C₄ photosynthesis during the induction period was investigated. When maize plants were illuminated (1400 μmol photon/m² · s) the rate of net photosynthesis gradually increased and reached a maximum rate after about 25 min. There was a similar increase in stomatal conductance during induction, indicating that stomatal opening tended to parallel the increase in photosynthesis. During the first 3–5 min of illumination the intercellular concentration of CO₂ gradually decreased below the atmospheric level and then reached a steady-state concentration (approx. 100–150 μl/l depending on the vapour pressure deficit). Thus, stomatal conductance does not limit photosynthesis during induction. Within a few minutes after illumination the stomata are regulated to maintain a relatively constant intercellular CO₂ concentration (C_i) which is near saturation for photosynthesis.