Some characteristics of photosynthetic inorganic carbon uptake of a marine macrophytic red alga |
| |
Authors: | C M. COOK B. COLMAN |
| |
Affiliation: | Department of Biology, York University, Downsview, Ontario, Canada |
| |
Abstract: | Abstract 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 CO2 [K1/2(CO2)] at pH 8.0 and 15°C was 21.4±3.0mmol m?3 CO2 under air, and 25.7±70mmol m?3 CO2 under N2. The corresponding values of Vmax were 2.98 ± 0.42 and 3.65±0.87 mmol O2 evolved g Chr?1 s?l. The apparent Km(CO2) of isolated ribulose bisphosphate carboxylase was determined at pH 8.0 and 30 °C to be 30.2 mmol m?3 CO2, and the corresponding value of Vmax was 19.67 μniol CO2 g protein?1 s?1. The CO2 compensation points of the thallus were measured in artificial seawater at pH 8.0 under air and N2, using a gas-chromatographic method. The values were relatively low, rising from 10 cm3 m?3 at 15°C, to 35 cm3 m?3 at 25°C, but were not affected by the O2 concentration. The lack of an effect of O2 on photosynthesis and on compensation point indicates that there is little photorespiratory CO2 loss in this macroalga. The high affinity of the thallus for CO2, and the low CO2 compensation concentrations, are consistent with the occurrence of bicarbonate uptake in this alga. |
| |
Keywords: | Palmarla palmate (Rhodymenia palmata) Rhodophyta photosynthesis CO2 compensation point photo-respiration temperature RuBP |
|
|