Abstract
A mass spectrometer with a membrane inlet was used to monitor light-driven O2 evolution, O2 uptake, and CO2 uptake in suspensions of algae (Scenedesmus obliquus). We observed the following. (a) The rate of O2 uptake, which, in the presence of iodoacetamide, replaces the uptake of CO2, showed a distinct plateau (Vmax) beyond ∼30% O2 and was half-maximal at ∼8% O2. We concluded that this light-driven O2 uptake process, which does not involve carbon compounds, is saturated at lower O2 concentrations than are photorespiration and glycolate formation. (b) In the absence of inhibitor, O2 evolution was relatively unaffected by the presence or absence of CO2. During the course of CO2 depletion, electron flow to CO2 was replaced by an equivalent flow to O2. (c) There was a distinct delay between the cessation of CO2 uptake and the increase in O2 uptake. We ascribe this delay to the transient utilization of another electron acceptor—possibly bicarbonate or another bound form of CO2.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Cheniae G. M., Martin I. F. Site of manganese function in photosynthesis. Biochim Biophys Acta. 1968 May 28;153(4):819–837. doi: 10.1016/0005-2728(68)90009-1. [DOI] [PubMed] [Google Scholar]
- Lex M., Silvester W. B., Stewart W. D. Photorespiration and nitrogenase activity in the blue-green alga, Anabaena cylindrica. Proc R Soc Lond B Biol Sci. 1972 Jan 18;180(1058):87–102. doi: 10.1098/rspb.1972.0007. [DOI] [PubMed] [Google Scholar]
- Radmer R. J., Kok B. Photoreduction of O(2) Primes and Replaces CO(2) Assimilation. Plant Physiol. 1976 Sep;58(3):336–340. doi: 10.1104/pp.58.3.336. [DOI] [PMC free article] [PubMed] [Google Scholar]