Carbon isotope analysis of acetaldehyde emitted from leaves following mechanical stress and anoxia

Abstract

Although the emission of acetaldehyde from plants into the atmosphere following biotic and abiotic stresses may significantly impact air quality and climate, its metabolic origin(s) remains uncertain. We investigated the pathway(s) responsible for the production of acetaldehyde in plants by studying variations in the stable carbon isotope composition of acetaldehyde emitted during leaf anoxia or following mechanical stress. Under an anoxic environment, C3 leaves produced acetaldehyde during ethanolic fermentation with a similar carbon isotopic composition to C3 bulk biomass. In contrast, the initial emission burst following mechanical wounding was 5–12‰ more depleted in 13C than emissions under anoxia. Due to a large kinetic isotope effect during pyruvate decarboxylation catalysed by pyruvate dehydrogenase, acetyl‐CoA and its biosynthetic products such as fatty acids are also depleted in 13C relative to bulk biomass. It is well known that leaf wounding stimulates the release of large quantities of fatty acids from membranes, as well as the accumulation of reactive oxygen species (ROS). We suggest that, following leaf wounding, acetaldehyde depleted in 13C is produced from fatty acid peroxidation reactions initiated by the accumulation of ROS. However, a variety of other pathways could also explain our results, including the conversion of acetyl‐CoA to acetaldehyde by the esterase activity of aldehyde dehydrogenase.

The effect of flow turbulence on growth, nutrient uptake and stable carbon and nitrogen isotope signatures inChara fibrosa

“…It is well known that the development of oxidative stress and accumulation of active oxygen molecules are responsible for lipid oxidation. Lipids are fairly less in 13 C; hence, lipid peroxidation may cause d 13 C values to be enriched in 13 C, in the plant material (Jardine et al, 2009). The plants exposed to high and medium turbulence were enriched in 13 C compared with the plants exposed to low turbulence, supporting the above hypothesis.…”

Detection of Plant Volatiles after Leaf Wounding and Darkening by Proton Transfer Reaction “Time-of-Flight” Mass Spectrometry (PTR-TOF)

“…Recent carbon isotope analysis indicated that wound-induced acetaldehyde burst in leaves is likely to derive from fatty acid oxidation rather than from transport from distant biosynthetic organs through the xylem flow [37]. Whether the acetaldehyde emission induced by wounding and light-dark transitions derives from fatty acid oxidation sharing the same branch reaction within the LOX pathway, or is the result of a different metabolic pathway present in leaves is still a matter of debate.…”

Bi-directional Exchange of Volatile Organic Compounds

“…Acetaldehyde emission sources in terrestrial ecosystems include soil and leaf litter in addition to plant canopies (Warneke et al 1999). Jardine et al (2009) used a stable carbon isotope as a tracer for characterizing multiple pathways for producing acetaldehyde in plants and also report that emissions were elevated following both leaf anoxia and mechanical stress. These findings highlight the complexity associated with accurately simulating the processes controlling just the emissions component of acetaldehyde emissions.…”

“…A uniform approach for modeling BDVOC exchange between terrestrial ecosystems and the atmosphere is needed. Jardine et al (2009) proposed a modeling approach based on ambient acetaldehyde concentration, a compensation point that is a function of light and temperature, and stomatal resistance to acetaldehyde but this technique was not implemented in a CTM. A simpler approach described by Millet et al (2010) was used in a CTM to estimate global distributions of acetaldehyde as a function of LAI, light and temperature.…”