Utilization of Exogenous Inorganic Carbon Species in Photosynthesis by Chlorella pyrenoidosa

Abstract
The nature of the inorganic carbon utilized during photosynthesis by Chlorella pyrenoidosa was investigated using three experimental techniques (open gas analysis system with “artificial leaf” or “aqueous” chambers and O2 electrode system) to measure carbon assimilation. Photosynthesis was studied as a function of pH and CO2 concentration. The CO2 concentration was inadequate to meet the requirements of photosynthesis only when HCO3 was added at high pH. Under all other conditions, the low and constant Km (CO2), in contrast to the highly variable Km (HCO3), suggested that CO2 was the major species utilized.