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First published online December 30, 2003; 10.1104/pp.103.030569 Plant Physiology 134:520-527 (2004) © 2004 American Society of Plant Biologists Respiratory Oxygen Uptake Is Not Decreased by an Instantaneous Elevation of [CO2], But Is Increased with Long-Term Growth in the Field at Elevated [CO2]1Departments of Crop Sciences and Plant Biology, University of Illinois, Urbana, Illinois 61801 (P.A.D., S.P.L., E.H.D.); Department of Biology, Queen's University, Kingston, Ontario, K7L 3N6, Canada (S.H.); Smithsonian Environmental Research Center, Edgewater, Maryland 21307 (G.J.H., B.R.D.); and School of Forest Resources and Environmental Science, Michigan Technological University, Houghton, Michigan 49931 (D.F.K.)
Averaged across many previous investigations, doubling the CO2 concentration ([CO2]) has frequently been reported to cause an instantaneous reduction of leaf dark respiration measured as CO2 efflux. No known mechanism accounts for this effect, and four recent studies have shown that the measurement of respiratory CO2 efflux is prone to experimental artifacts that could account for the reported response. Here, these artifacts are avoided by use of a high-resolution dual channel oxygen analyzer within an open gas exchange system to measure respiratory O2 uptake in normal air. Leaf O2 uptake was determined in response to instantaneous elevation of [CO2] in nine contrasting species and to long-term elevation in seven species from four field experiments. Over six hundred separate measurements of respiration failed to reveal any decrease in respiratory O2 uptake with an instantaneous increase in [CO2]. Respiration was found insensitive not only to doubling [CO2], but also to a 5-fold increase and to decrease to zero. Using a wide range of species and conditions, we confirm earlier reports that inhibition of respiration by instantaneous elevation of [CO2] is likely an experimental artifact. Instead of the expected decrease in respiration per unit leaf area in response to long-term growth in the field at elevated [CO2], there was a significant increase of 11% and 7% on an area and mass basis, respectively, averaged across all experiments. The findings suggest that leaf dark respiration will increase not decrease as atmospheric [CO2] rises.
1 This work was supported by the U.S. Department of Energy's Office of Science (to B.E.R.), as were the long-term elevated [CO2] experiments in Florida, North Carolina, and Wisconsin. 2 Present address: Department of Biological Sciences, University of Essex, Colchester, CO4 3SQ, UK. 3 Present address: Dipartimento di Scienze dell' Ambiente Forestale e delle Sue Risorse, Università della Tuscia, Via S. Camillo de Lellis, 01100 Viterbo, Italy. Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.103.030569. * Corresponding author; e-mail stevel{at}life.uiuc.edu; fax 217-244-7563. Received July 20, 2003; returned for revision August 20, 2003; accepted September 25, 2003. This article has been cited by other articles:
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