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The Uptake of Free CO 2 and HCO 3 ‐ during Photosynthesis of Plankton Algae with Special Reference to the Coccolithophorid Coccolithus huxleyi
Author(s) -
Nielsen E. Steemann
Publication year - 1966
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1966.tb09095.x
Subject(s) - photosynthesis , bicarbonate , ion , chemistry , botany , biology , biochemistry , organic chemistry
From a re‐evaluation of experiments with the coccolithophorid Coccolithus hurleyi made by Paasche (1964), curves are presented showing the rate of photosynthesis as a function of the concentration of both free CO 2 and bicarbonate CO 2 . It is shown that photosynthesis in a naked clone is due only to the uptake of free CO 2 . The problem concerning the high concentration of free CO 2 necessary for photosynthesis in Coccolithus huxleyi is discussed. It is shown that it is not due to lack of the enzyme carbonic anhydrase. Hence it is probable that the formation of coccoliths is the mechanism by which, in Coccolithus, the utilization of HCO 3 ‐ ions in photosynthesis becomes possible. The OH ‐ ions produced during photosynthesis ( + Ca 2+ taken up together with the HCO 3 ‐ ions) are thus neutralized. This situation is different from other aquatics utilizing HCO 3 ‐ in photosynthesis. Here the OH ‐ ions are neutralized via an ion exchange of Ca 2+ with H + in the surrounding medium.