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 K_m (CO₂), in contrast to the highly variable K_m (HCO₃⁻), suggested that CO₂ was the major species utilized.