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| Titel |
Environmental controls over methanol emission from leaves |
| VerfasserIn |
P. Harley, J. Greenberg, Ü. Niinemets, A. Guenther |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 4, no. 6 ; Nr. 4, no. 6 (2007-12-05), S.1083-1099 |
| Datensatznummer |
250002000
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| Publikation (Nr.) |
 copernicus.org/bg-4-1083-2007.pdf |
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| Zusammenfassung |
Methanol is found throughout the troposphere, with average concentrations
second only to methane among atmospheric hydrocarbons. Proposed global
methanol budgets are highly uncertain, but all agree that at least 60% of
the total source arises from the terrestrial biosphere and primary emissions
from plants. However, the magnitude of these emissions is also highly
uncertain, and the environmental factors which control them require further
elucidation.
Using a temperature-controlled leaf enclosure, we measured methanol
emissions from leaves of six plant species by proton transfer reaction mass
spectrometry, with simultaneous measurements of leaf evapotranspiration and
stomatal conductance. Rates of emission at 30°C varied from 0.2 to
38 μg g (dry mass)−1 h−1, with higher rates measured on young
leaves, consistent with the production of methanol via pectin demethylation
in expanding foliage. On average, emissions increased by a factor of 2.3 for
each 10°C increase in leaf temperature. At constant temperature,
emissions were also correlated with co-varying incident photosynthetic
photon flux density and rates of stomatal conductance. The data were
analyzed using the emission model developed by Niinemets and Reichstein
(2003a, b), with the incorporation of a methanol production term that
increased exponentially with temperature. It was concluded that control of
emissions, during daytime, was shared by leaf temperature and stomatal
conductance, although rates of production may also vary diurnally in
response to variations in leaf growth rate in expanding leaves. The model,
which generally provided reasonable simulations of the measured data during
the day, significantly overestimated emissions on two sets of measurements
made through the night, suggesting that production rates of methanol were
reduced at night, perhaps because leaf growth was reduced or possibly
through a direct effect of light on production. Although the short-term
dynamics of methanol emissions can be successfully modeled only if
stomatal conductance and compound solubility are taken into account,
emissions on longer time scales will be
determined by rates of methanol production, controls over which remain to be
investigated. |
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