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Photosynthesis and conductance of spring-wheat leaves: field response to continuous free-air atmospheric CO2 enrichment

Garcia, R.L., Long, S.P., Wall, G.W., Osborne, C.P., Kimball, B.A., Nie, G.Y., Pinter, P.J., Lamorte, R.L. and Wechsung, F. (1998) Photosynthesis and conductance of spring-wheat leaves: field response to continuous free-air atmospheric CO2 enrichment. Plant, Cell & Environment, 21 (7). pp. 659-669. ISSN 0140-7791


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Spring wheat was grown from emergence to grain maturity in two partial pressures of CO2 (pCO2): ambient air of nominally 37 Pa and air enriched with CO2 to 55 Pa using a free-air CO2 enrichment (FACE) apparatus. This experiment was the first of its kind to be conducted within a cereal field without the modifications or disturbance of microclimate and rooting environment that accompanied previous studies. It provided a unique opportunity to examine the hypothesis that continuous exposure of wheat to elevated pCO2 will lead to acclimatory loss of photosynthetic capacity. The diurnal courses of photosynthesis and conductance for upper canopy leaves were followed throughout the development of the crop and compared to model-predicted rates of photosynthesis. The seasonal average of midday photosynthesis rates was 28% greater in plants exposed to elevated pCO2 than in contols and the seasonal average of the daily integrals of photosynthesis was 21% greater in elevated pCO2 than in ambient air. The mean conductance at midday was reduced by 36%. The observed enhancement of photosynthesis in elevated pCO2 agreed closely with that predicted from a mechanistic biochemical model that assumed no acclimation of photosynthetic capacity. Measured values fell below predicted only in the flag leaves in the mid afternoon before the onset of grain-filling and over the whole diurnal course at the end of grain-filling. The loss of enhancement at this final stage was attributed to the earlier senescence of flag leaves in elevated pCO2. In contrast to some controlled-environment and field-enclosure studies, this field-scale study of wheat using free-air CO2 enrichment found little evidence of acclimatory loss of photosynthetic capacity with growth in elevated pCO2 and a significant and substantial increase in leaf photosynthesis throughout the life of the crop.

Item Type: Article
Copyright, Publisher and Additional Information: 'This is an electronic version of an Article published in Plant, Cell and Environment, July 1998, vol. 21, no. 7, pp. 659-669'. © 1998 Blackwell Publishing Ltd
Institution: The University of Sheffield
Academic Units: The University of Sheffield > Faculty of Science (Sheffield) > School of Biological Sciences (Sheffield) > Department of Animal and Plant Sciences (Sheffield)
Depositing User: Repository Officer
Date Deposited: 24 Aug 2004
Last Modified: 06 Jun 2014 18:05
Status: Published
Refereed: Yes
URI: http://eprints.whiterose.ac.uk/id/eprint/62

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