Abstract
The macroscopic cyanophyte Lyngbya birgei G.M. Smith can form extensive floating mats and become an aquatic weed. This organism, when grown in the laboratory under low or relatively high inorganic carbon concentrations (0.1 or 1.0 mM HCO3-, representing a range found in nature), showed photosynthetic K 1 2 values for inorganic carbon of 20 and 40 μM when using mainly CO2 (pH 5.5) and HCO3- (pH 9.0), respectively. Comparisons of photosynthetic rates and maximal uncatalyzed HCO3- dehydration rates indicated HCO3- uptake at the higher pH. Only at an unnaturally high inorganic carbon growth concentration (10 mM) did the affinity for HCO3- decrease. Inorganic carbon was concentrated internally in Lyngbya up to eight times external levels by a light and HCO3- (but apparently not CO2) dependent process. Internal inorganic carbon levels were about 2 mM at a range of ambient inorganic carbon concentrations occurring in mats. It is suggested that a resulting elevated internal CO2 level is the basis for the ability of this cyanophyte to suppress photorespiration. The efficient use of HCO3- and the capability to concentrate inorganic carbon are seen as adaptive features which optimize photosynthetic production of Lyngbya in mats, where HCO3- is the principal external carbon source available for photosynthesis and O2 levels are high during the day.
Original language | English |
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Pages (from-to) | 159-171 |
Number of pages | 13 |
Journal | Aquatic Botany |
Volume | 42 |
Issue number | 2 |
DOIs | |
State | Published - Jan 1992 |
Externally published | Yes |