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Comparison of Gas Exchange and Bioassay Determinations of the Ammonia Compensation Point in Luzula sylvatica (Huds.) Gaud

Hill, Paul W.; Raven, John A.; Loubet, Benjamin; Fowler, David; Sutton, Mark A.. 2001 Comparison of Gas Exchange and Bioassay Determinations of the Ammonia Compensation Point in Luzula sylvatica (Huds.) Gaud. Plant Physiology, 125. 476-487.

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Abstract/Summary

Determinations of the NH3 compensation point for the understory plant of semi-natural woodlands Luzula sylvatica (Huds.) Gaud. were carried out by measurements of gas exchange and by calculation from the NH4+ concentration and pH of extracts of the foliar apoplast. Compensation points determined by gas exchange measurements were among the lowest yet reported (0.51-1.10 µg NH3 m3) and those calculated from apoplast extracts were lower than any yet reported (0.017-0.54 µg NH3 m3). Those determined by gas exchange were consistently found to be between 2 and 30 times higher than those determined from apoplast extracts. Consideration of possible causes of this discrepancy, which is not confined to this investigation, showed that all likely errors would result in an increase in the discrepancy, or were insufficient to account for observed differences. It is suggested that spatial variability of pH and NH4+ concentration within the foliar apoplast represents the most promising line for further investigation. It is also shown that the foliar apoplast of L. sylvatica is sufficiently buffered to eliminate the need for correction of H+ concentration for dilution during extraction, but that it is necessary to correct the NH4+ concentration of apoplast extracts for dilution

Item Type: Publication - Article
Programmes: CEH Programmes pre-2009 publications > Biogeochemistry
CEH Sections: _ Atmospheric Sciences
NORA Subject Terms: Botany
Ecology and Environment
Atmospheric Sciences
Date made live: 04 Sep 2008 08:52
URI: http://nora.nerc.ac.uk/id/eprint/3695

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