Form of inorganic carbon utilized for photosynthesis in Chlorella vulgaris 11h cells

概要

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The rate of photosynthetic ^<14>CO_2 fixation in Chlorella vulgaris 11 h cells in the presence of 0.55 m_M NaH^<14>CO_3 at pH 8.0 (20℃) was greatly enhanced by the addition of carbonic anhydrase (CA). However, when air containing 400 ppm ^<14>CO_2 was bubbled through the algal suspension, the rate of ^<14>CO_2 fixation immediately after the start of the bubbling was suppressed by CA. These effects of CA were observed in cells which had been grown in air containing 2% CO_2 (high-CO_2 cells) as well as those grown in ordinary air (containing 0.04% CO_2, low-CO_2 cells) . We therefore concluded that, irrespective of the CO_2 concentration given to the algal cells during growth, the active species of inorganic carbon absorbed by Chlorella cells is free CO_2 and they cannot utilize bicarbonate. The effects observed in the high-CO_2 cells were much more pronounced than those in the low-CO_2 cells. This difference was accounted for by the difference in the affinity for CO_2 in photosynthesis between the high- and low-CO_2 cells.
日本植物生理学会の論文