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Some characteristics of photosynthetic inorganic carbon uptake of a marine macrophytic red alga
Author(s) -
COOK C M.,
COLMAN B.
Publication year - 1987
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/1365-3040.ep11602301
Subject(s) - thallus , photosynthesis , bicarbonate , botany , seawater , carbon dioxide , compensation point , rubisco , photorespiration , total inorganic carbon , chemistry , artificial seawater , biology , ecology , organic chemistry , transpiration
Some characteristics of photosynthetic inorganic carbon uptake by Palmaria palmata , a marine red macroalga, have been measured under physiological conditions in artificial seawater. The apparent affinity of thallus for CO 2 [K 1/2 (CO 2 )] at pH 8.0 and 15°C was 21.4±3.0mmol m −3 CO 2 under air, and 25.7±70mmol m −3 CO 2 under N 2 . The corresponding values of V max were 2.98 ± 0.42 and 3.65±0.87 mmol O 2 evolved g Chr −1 s −l . The apparent K m (CO 2 ) of isolated ribulose bisphosphate carboxylase was determined at pH 8.0 and 30 °C to be 30.2 mmol m −3 CO 2 , and the corresponding value of V max was 19.67 μniol CO 2 g protein −1 s −1 . The CO 2 compensation points of the thallus were measured in artificial seawater at pH 8.0 under air and N 2 , using a gas‐chromatographic method. The values were relatively low, rising from 10 cm 3 m −3 at 15°C, to 35 cm 3 m −3 at 25°C, but were not affected by the O 2 concentration. The lack of an effect of O 2 on photosynthesis and on compensation point indicates that there is little photorespiratory CO 2 loss in this macroalga. The high affinity of the thallus for CO 2 , and the low CO 2 compensation concentrations, are consistent with the occurrence of bicarbonate uptake in this alga.