O2 Uptake in the Light in Chlamydomonas
- 1 September 1985
- journal article
- research article
- Published by Oxford University Press (OUP) in Plant Physiology
- Vol. 79 (1) , 225-230
- https://doi.org/10.1104/pp.79.1.225
Abstract
The nature of the process responsible for the stationary O2 uptake occurring in the light under saturating CO2 concentration in Chlamydomonas reinhardii has been investigated. For this purpose, a mass spectrometer with a membrane inlet system was used to measure O2 uptake and evolution in the algal suspension. First, we observed that the O2 uptake rate was constant (about 0.5 micromoles of O2 per milligram chlorophyll per minute) during a light to dark transition and was not affected by 3-(3,4-dichlorophenyl)-1,1-dimethylurea. Salicylhydroxamic acid had no effect on O2 uptake in the dark or in the light, but was found to have the same inhibitory effect either in the dark or in the light when added to cyanide-treated algae. The stimulation of the O2 uptake rate due to the uncoupling effect of carbonyl cyanide m-chlorophenylhydrazone was about the same in the dark or in the light. From these results, we conclude that mitochondrial respiration is maintained during illumination and therefore is not inhibited by high ATP levels. Another conclusion is that in conditions where photorespiration is absent, no other light-dependent O2 uptake process occurs. If Mehler reactions are involved, in Chlamydomonas, under conditions where both photosynthetic carbon oxidation and reduction cycles cannot operate (as in cyanide-treated algae), their occurrence in photosynthesizing algae either under saturating CO2 concentration or at the CO2 compensation point appears very unlikely. The comparison with the situation previously reported in Scenedesmus (R. J. Radmer and B. Kol 1976 Plant Physiol 58: 336-340) suggests that different O2 uptake processes might be present in these two algal species.This publication has 20 references indexed in Scilit:
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