Oxygen Uptake and Photosynthesis of the Red Macroalga, Chondrus crispus, in Seawater

Abstract

ABSTRACIWith an experimental system developed for aquatic plants using the mass spectrometry technique and infrared gas analysis of C02, we studied the responses to various 02 concentrations of gas exchanges with the red macroalga Choadrus crispus S. The results were as follows. (a) (3,22). Some authors postulated that a limitation in RuBP regeneration might explain these discrepancies (9). But also, these discrepancies suggest that: (a) the Rubisco enzyme differs either as it is isolated or placed in its functional cellular environment; or (b) the Rubisco enzyme is not involved in all of the 02 photoconsumption. From several reports on higher plants (2,(16)(17)(18)25) and microalgae (7,11,15,21,26,(28)(29)(30) organisms. Furthermore, some microalgae have presented gas exchange kinetics in contradiction with the expected competition between 02 and CO2 at the Rubisco enzyme level for photochemically generated reducing equivalents (15,29,30), and exhibit no detectable photorespiration as measured by CO2 release in the light (24,30).In a previous study (6), we observed that 02 uptake in the light in the marine macroalga, Chondrus crispus Stackhouse (Rhodophyta, Gigartinales), was relatively insensitive to CO2 concentration. We concluded that the glycolate pathway was not mainly involved. We tested this hypothesis by studying the effects of 02 on the gas exchanges of this alga at various CO2 concentrations, and particularly the 02 and light sensitivities of02 uptake in the light under conditions of high CO2.MATERIALS AND METHODS Plant Material. Experiments reported here were made on the carrageen red macroalga Chondrus crispus Stackhouse from the English Channel. Origin and cultural conditions were previously described in detail (6). As in our previous studies (5, 6), we used the S7 strain (first and second batch) selected for several years and cultivated in outdoor tanks by the CECA Company (50500 Carentan, France) for industrial carrageenan extraction. The selection pressure resulted in the preponderance ofgametophytic stages (more than 90%), which contain polysaccharides of higher industrial interest. We also used wild thalli (third batch) that we collected on the French coast of La Manche (St. Cast, Cotes du Nord).Because of seasonal variations, comparison between different batches put in our stable cultural conditions at various times were not strictly possible. This is the reason why, as far as possible, we retested both 02 and CO2 concentration on each batch isolated from outdoor conditions in October (first batch), November (second batch), and at the end of December 1983 (third batch). Each batch was big enough to provide for at least 10 samples ranging from 15 to 25 g FW.Experimental System. For this study, we used the experimental apparatus previously described (5), consisting of a thermoregulated chamber, which contained 3 L of seawater strongly aerated with a high flow rate (120 L.h-') of gas. It was connected in a semiclosed circuit to a line of analysis and regulation of gaseous concentrations includ...

Effect of Photon Fluence Rate on Oxygen Evolution and Uptake by Chlamydomonas reinhardtii Suspensions Grown in Ambient and CO2-Enriched Air

“…However, it appears that dark respiration was only slightly affected by assimilation in the preceding light period. This is supported by reports from other laboratories suggesting that the rates of mitochondrial 02 uptake in the light were the same (7,17) or lower than in the dark (22). If this is true, then UO is several fold higher than dark respiration in C02-grown and airgrown cells (Figs.…”

“…The Mehler reaction will contribute to UO (7,9,16). Additionally, U. will be increased in plants with an active PCO cycle (5,6,8), or when mitochondrial electron flow proceeds in the light (10,11,18,22).…”

Mechanism of Photosynthetic Carbon Dioxide Uptake by the Red Macroalga, Chondrus crispus

“…2) (24). C. crispus and other marine macroalgae saturate at Ci levels near 2 mM or higher (this study; also see 2,4,8,25,28). In contrast, cyanobacteria and green algae, which actively accumulate Ci, are saturated at levels less than 0.1 mm Ci (1,19).…”

“…The mixture was bubbled with a gas mixture containing 5% CO2 and 95% N2 (Analyzed Gases, Liquid Carbonic Ltd., Toronto) at 100 mL.min-' and the time required for the pH to drop from 8 …”

“…This suggestion is based on the ability of macroalgae to photosynthesize at pH values above 8.0 (2,4,9,10,25), and on their C4-like photosynthetic physiology, e.g. low photorespiratory rates (2,4,8,11,13), low C, compensation points (4,12,13), and intermediate Km (C02) Rubisco values (13). In one study (14), it was shown that several marine macroalgae actively transport Ci for photosynthesis, although no mechanism was…”