Journal of PhycologyVolume 27, Issue 1 p. 14-20 EFFECTS OF INORGANIC N AVAILABILITY ON ALGAL PHOTOSYNTHESIS AND CARBON METABOLISM David H. Turpin, David H. Turpin Department of Biology, Queen's University, Kingston, Ontario, Canada K7L 3N6Search for more papers by this author David H. Turpin, David H. Turpin Department of Biology, Queen's University, Kingston, Ontario, Canada K7L 3N6Search for more papers by this author First published: February 1991 https://doi.org/10.1111/j.0022-3646.1991.00014.xCitations: 293 Supported by the Natural Sciences and Engineering Research Council of Canada. Special thanks are due Drs. J. Beardall, D. Bruce, P. G. Falkowski, G. Forti, M. Guerrero, C. Lara, C. M. Larsson, F. G. Plumley, M. Ohmori, J. Raven, G. Schmidt, W. R. Ullrich, and J. M. Vega for providing helpful input and access to unpublished manuscripts and observations. I also thank Lizabeth Jasvins and Jo-Anne Lorway for their help in manuscript preparation. Question (Davison): Phycologists interested in rates of primary productivity frequently use oxygen evolution to measure photosynthesis, converting these data to carbon fixation using a PQ of 1.0. Is this valid in view of the effect of nitrogen metabolism on photosynthesis and respiration and what magnitude of error might result? Answer: Photosynthetic quotients are one of the most abused indices in phytoplankton physiological ecology. Most reported PQs are determined from measurements of gross carbon fixation (14C) and net O2 exchange. As a result, O2 evolution is biased by respiratory O2 consumption during photosynthesis. To be truly useful in PQ analysis, carbon fixation and O2 evolution must both be determined as either a gross or a net measure. This would yield either gross or net PQs, which would provide some very useful information. The utility of PQ analysis in primary productivity is in need of a rigorous critical reassessment. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume27, Issue1February 1991Pages 14-20 RelatedInformation