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| Titel |
The effect of flooding on the exchange of the volatile C2-compounds ethanol, acetaldehyde and acetic acid between leaves of Amazonian floodplain tree species and the atmosphere |
| VerfasserIn |
S. Rottenberger, B. Kleiss, U. Kuhn, A. Wolf, M. T. F. Piedade, W. Junk, J. Kesselmeier |
| 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 ; 5, no. 4 ; Nr. 5, no. 4 (2008-08-01), S.1085-1100 |
| Datensatznummer |
250002680
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| Publikation (Nr.) |
 copernicus.org/bg-5-1085-2008.pdf |
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| Zusammenfassung |
| The effect of root inundation on the leaf emissions of ethanol, acetaldehyde
and acetic acid in relation to assimilation and transpiration was
investigated with 2–3 years old tree seedlings of four Amazonian floodplain
species by applying dynamic cuvette systems under greenhouse conditions.
Emissions were monitored over a period of several days of inundation using a
combination of Proton Transfer Reaction Mass Spectrometry (PTR-MS) and
conventional techniques (HPLC, ion chromatography). Under non-flooded
conditions, none of the species exhibited measurable emissions of any of the
compounds, but rather low deposition of acetaldehyde and acetic acid was
observed instead. Tree species specific variations in deposition velocities
were largely due to variations in stomatal conductance. Flooding of the
roots resulted in leaf emissions of ethanol and acetaldehyde by all species,
while emissions of acetic acid were only observed from the species
exhibiting the highest ethanol and acetaldehyde emission rates. All three
compounds showed a similar diurnal emission profile, each displaying an
emission burst in the morning, followed by a decline in the evening. This
concurrent behavior supports the conclusion, that all three compounds
emitted by the leaves are derived from ethanol produced in the roots by
alcoholic fermentation, transported to the leaves with the transpiration
stream and finally partly converted to acetaldehyde and acetic acid by
enzymatic processes. Co-emissions and peaking in the early morning suggest
that root ethanol, after transportation with the transpiration stream to the
leaves and enzymatic oxidation to acetaldehyde and acetate, is the metabolic
precursor for all compounds emitted, though we can not totally exclude other
production pathways. Emission rates substantially varied among tree species,
with maxima differing by up to two orders of magnitude (25–1700 nmol m−2 min−1
for ethanol and 5–500 nmol m−2 min−1 for acetaldehyde). Acetic acid emissions reached 12 nmol m−2 min−1.
The observed differences in emission rates between the tree species are
discussed with respect to their root adaptive strategies to tolerate long
term flooding, providing an indirect line of evidence that the root ethanol
production is a major factor determining the foliar emissions. Species which
develop morphological root structures allowing for enhanced root aeration
produced less ethanol and showed much lower emissions compared to species
which lack gas transporting systems, and respond to flooding with
substantially enhanced fermentation rates and a non-trivial loss of carbon
to the atmosphere. The pronounced differences in the relative emissions of
ethanol to acetaldehyde and acetic acid between the tree species indicate
that not only the ethanol production in the roots but also the metabolic
conversion in the leaf is an important factor determining the release of
these compounds to the atmosphere. |
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