Abstract
Abstract. We quantified fine scale sources and sinks of gas phase acetaldehyde in two forested ecosystems in the US. During the daytime, the upper canopy behaved as a net source while at lower heights, reduced emission rates or net uptake were observed. At night, uptake generally predominated throughout the canopies. Net ecosystem emission rates were inversely related to foliar density due to the extinction of light in the canopy and a respective decrease of the acetaldehyde compensation point. This is supported by branch level studies revealing much higher compensation points in the light than in the dark for poplar (Populus deltoides) and holly oak (Quercus ilex) implying a higher light/temperature sensitivity for acetaldehyde production relative to consumption. The view of stomata as the major pathway for acetaldehyde exchange is supported by strong linear correlations between branch transpiration rates and acetaldehyde exchange velocities for both species. In addition, natural abundance carbon isotope analysis of gas-phase acetaldehyde during poplar branch fumigation experiments revealed a significant kinetic isotope effect of 5.1±0.3‰ associated with the uptake of acetaldehyde. Similar experiments with dry dead poplar leaves showed no fractionation or uptake of acetaldehyde, confirming that this is only a property of living leaves. We suggest that acetaldehyde belongs to a potentially large list of plant metabolites where stomatal resistance can exert long term control over both emission and uptake rates due to the presence of both source(s) and sink(s) within the leaf which strongly buffer large changes in concentrations in the substomatal airspace due to changes in stomatal resistance. We conclude that the exchange of acetaldehyde between plant canopies and the atmosphere is fundamentally controlled by ambient acetaldehyde concentrations, stomatal resistance, and the compensation point which is a function of light/temperature.
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Claims 10
Claim · model-written summary
Upper canopy was a net daytime acetaldehyde source while lower canopy had reduced emissions or uptake.
Verbatim
e0“During the daytime, the upper canopy behaved as a net source while at lower heights, reduced emission rates or net uptake were observed.”
t0“forest canopies”
Claim · model-written summary
At night, acetaldehyde uptake predominated throughout forest canopies.
Verbatim
e0“At night, uptake generally predominated throughout the canopies.”
t0“forest canopies”
Claim · model-written summary
Net ecosystem acetaldehyde emissions were inversely related to foliar density.
Verbatim
e0“Net ecosystem emission rates were inversely related to foliar density due to the extinction of light in the canopy and a respective decrease of the acetaldehyde compensation point.”
t0“forest canopies”
Claim · model-written summary
Poplar acetaldehyde compensation points were higher in light than dark.
PopulusOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“much higher compensation points in the light than in the dark for poplar (Populus deltoides) and holly oak (Quercus ilex)”
Claim · model-written summary
Holly oak acetaldehyde compensation points were higher in light than dark.
- Taxon
- holly oak
Quercus ilexe0 - Outcome
- compensation pointse0
- Direction
- highere0
- Comparator
- in the darke0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“much higher compensation points in the light than in the dark for poplar (Populus deltoides) and holly oak (Quercus ilex)”
Claim · model-written summary
In both species, branch transpiration and acetaldehyde exchange velocities were strongly linearly correlated.
- Taxon
- poplar (Populus deltoides) and holly oak (Quercus ilex)
Populus deltoidesQuercus ilexe1 - Organ / stage
- branche0
- Outcome
- acetaldehyde exchange velocitiese0
- Qualifier
- strong linear correlations between branch transpiration rates and acetaldehyde exchange velocitiese0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“strong linear correlations between branch transpiration rates and acetaldehyde exchange velocities for both species”
e1“poplar (Populus deltoides) and holly oak (Quercus ilex)”
Claim · model-written summary
Living poplar branches showed a significant 5.1±0.3‰ kinetic isotope effect during acetaldehyde uptake.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“natural abundance carbon isotope analysis of gas-phase acetaldehyde during poplar branch fumigation experiments revealed a significant kinetic isotope effect of 5.1±0.3‰ associated with the uptake of acetaldehyde.”
Claim · model-written summary
Dry dead poplar leaves showed neither acetaldehyde fractionation nor uptake.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Similar experiments with dry dead poplar leaves showed no fractionation or uptake of acetaldehyde”
Claim · model-written summary
The authors propose that stomatal resistance can control long term acetaldehyde exchange because leaves contain both sources and sinks.
Verbatim
e0“stomatal resistance can exert long term control over both emission and uptake rates due to the presence of both source(s) and sink(s) within the leaf”
t0“forest canopies”
Claim · model-written summary
The authors conclude ambient acetaldehyde, stomatal resistance and light or temperature dependent compensation points govern exchange.
Verbatim
e0“the exchange of acetaldehyde between plant canopies and the atmosphere is fundamentally controlled by ambient acetaldehyde concentrations, stomatal resistance, and the compensation point which is a function of light/temperature.”
t0“forest canopies”