Uptake of Inorganic Carbon by Isolated Chloroplasts of the Unicellular Green Alga Chlorella ellipsoidea

Chloroplasts, isolated from protoplasts of the green alga, Chlorella ellipsoidea, were estimated to be 99% intact by the ferricyanide-reduction assay, and gave CO(2) and PGA-dependent rates of O(2) evolution of 64.5 to 150 micromoles per milligram of chlorophyll per hour, that is 30 to 70% of the photosynthetic activity of the parent cells. Intact chloroplasts showed no carbonic anhydrase activity, but it was detected in preparations of ruptured organelles. Rates of photosynthesis, measured in a closed system at pH 7.5, were twice the calculated rate of CO(2) supply from the uncatalyzed dehydration of HCO(3) (-) indicating a direct uptake of bicarbonate by the intact chloroplasts. Mass spectrometric measurements of CO(2) depletion from the medium on the illumination of chloroplasts indicate the lack of an active CO(2) transport across the chloroplast envelope.