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Leaf-Atmosphere NH3 Exchange in Barley Mutants with Reduced Activities of Glutamine Synthetase

Mattsson, M., Hausler, R.E., Leegood, R.C., Lea, P.J. and Schjoerring, J.K. (1997) Leaf-Atmosphere NH3 Exchange in Barley Mutants with Reduced Activities of Glutamine Synthetase. Plant Physiology, 114 (4). pp. 1307-1312. ISSN 0032-0889


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Mutants of barley (Hordeum vulgare L. cv Maris Mink) with 47 or 66% of the glutamine synthetase (GS) activity of the wild type were used for studies of NH3 exchange with the atmosphere. Under normal light and temperature conditions, tissue NH4+ concentrations were higher in the two mutants compared with wild-type plants, and this was accompanied by higher NH3 emission from the leaves. The emission of NH3 increased with increasing leaf temperatures in both wild-type and mutant plants, but the increase was much more pronounced in the mutants. Similar results were found when the light intensity (photosynthetic photon flux density) was increased. Compensation points for NH3 were estimated by exposing intact shoots to 10 nmol NH3 mol-1 air under conditions with increasing temperatures until the plants started to emit NH3. Referenced to 25[deg]C, the compensation points were 5.0 nmol mol-1 for wild-type plants, 8.3 nmol mol-1 for 47% GS mutants, and 11.8 nmol mol-1 for 66% GS mutants. Compensation points for NH3 in single, nonsenescent leaves were estimated on the basis of apoplastic pH and NH4+ concentrations. These values were 0.75, 3.46, and 7.72 nmol mol-1 for wild type, 47% GS mutants, and 66% GS mutants, respectively. The 66% GS mutant always showed higher tissue NH4+ concentrations, NH3 emission rates, and NH3 compensation points compared with the 47% GS mutant, indicating that NH4+ release was curtailed by some kind of compensatory mechanism in plants with only 47% GS activity

Item Type: Article
Copyright, Publisher and Additional Information: Copyright © 1997 by the American Society of Plant Biologists
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)
The University of Sheffield > University of Sheffield Research Centres and Institutes > Robert Hill Institute (Sheffield)
Depositing User: Repository Officer
Date Deposited: 22 Oct 2004
Last Modified: 05 Jun 2014 05:08
Status: Published
Refereed: Yes
URI: http://eprints.whiterose.ac.uk/id/eprint/162

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