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Detection of plant volatiles after leaf wounding and darkening by proton transfer reaction "time-of-flight" mass spectrometry (PTR-TOF).

Brilli F, Ruuskanen TM, Schnitzhofer R, Müller M, Breitenlechner M, Bittner V, Wohlfahrt G, Loreto F, Hansel A - PLoS ONE (2011)

Bottom Line: In the strong isoprene-emitter Populus alba, light-dependent isoprene emission was sustained and even enhanced for hours after photosynthesis inhibition due to leaf cutting.Thus isoprene emission can uncouple from photosynthesis and may occur even after cutting leaves or branches, e.g., by agricultural practices or because of abiotic and biotic stresses.This observation may have important implications for assessments of isoprene sources and budget in the atmosphere, and consequences for tropospheric chemistry.

View Article: PubMed Central - PubMed

Affiliation: Ionicon Analytik G.m.b.H., Innsbruck, Austria.

ABSTRACT
Proton transfer reaction-time of flight (PTR-TOF) mass spectrometry was used to improve detection of biogenic volatiles organic compounds (BVOCs) induced by leaf wounding and darkening. PTR-TOF measurements unambiguously captured the kinetic of the large emissions of green leaf volatiles (GLVs) and acetaldehyde after wounding and darkening. GLVs emission correlated with the extent of wounding, thus confirming to be an excellent indicator of mechanical damage. Transient emissions of methanol, C5 compounds and isoprene from plant species that do not emit isoprene constitutively were also detected after wounding. In the strong isoprene-emitter Populus alba, light-dependent isoprene emission was sustained and even enhanced for hours after photosynthesis inhibition due to leaf cutting. Thus isoprene emission can uncouple from photosynthesis and may occur even after cutting leaves or branches, e.g., by agricultural practices or because of abiotic and biotic stresses. This observation may have important implications for assessments of isoprene sources and budget in the atmosphere, and consequences for tropospheric chemistry.

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Ratios between the normalized emission rates Ek (t)                            varying over the time.Different panels indicate ratios of                                m/z = 83.085/m/z = 81.070                            (a) and m/z 143.107/m/z 81.070 (b)                            emitted after cutting leaves of Dactlylis glomerata                            (red lines) and of Populus alba (dark red lines) or                            after exposing to light to dark transition leaves of Dactlylis                                glomerata (blue lines) and of Populus alba                            (dark blue lines).
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pone-0020419-g007: Ratios between the normalized emission rates Ek (t) varying over the time.Different panels indicate ratios of m/z = 83.085/m/z = 81.070 (a) and m/z 143.107/m/z 81.070 (b) emitted after cutting leaves of Dactlylis glomerata (red lines) and of Populus alba (dark red lines) or after exposing to light to dark transition leaves of Dactlylis glomerata (blue lines) and of Populus alba (dark blue lines).

Mentions: In vivo information on the enzymatic activity leading to GLVs production cannot be provided according to Michealis-Menten model due to difficult estimation of substrate availability. This is the consequence of the continuous conversion of enzymatic products into further substrates which occurs once the cascade of multi-step enzymatic reaction (catalyzed by LOX, HPL, ADH and AD) has been initiated. However, by exploiting PTR-TOF highly resolved GLVs analysis, it may be possible to indirectly analyze differences in the activation of the lipoxygenase pathway by following the rate of conversion over the time between ratios of protonated ions. In particular the time course of the ratios between m/z = 83.085/81.070 (hexenols + hexanal/hexenals) and between m/z = 143.107/81.070 (hexenyl acetates/hexenals) may provide information about the speed of conversion of the classes of GLVs. We performed this analysis on GLVs emitted after cutting and after transition from light to dark transition by D. glomerata and P. alba leaves (Fig. 7 a,b). Our results show that wounding induces a differential production of the main GLVs over the time with respect to light-dark transition in both plant species. The instantaneous oxidation of linoleic and α-linolenic acids occurring when wounded cellular membranes are exposed to the air contact efficiently catalyzed the first step of the lipoxygenase reactions leading to the production of m/z = 81.070 (hexanal/hexenals) that is slowly converted to m/z = 83.085 (hexenols) and then to m/z = 143.107 (hexenyl acetates); differently the condition created by sudden darkening induces a production of both m/z = 81.070 than m/z = 83.085 (or m/z = 143.107) with similar time-courses.


Detection of plant volatiles after leaf wounding and darkening by proton transfer reaction "time-of-flight" mass spectrometry (PTR-TOF).

Brilli F, Ruuskanen TM, Schnitzhofer R, Müller M, Breitenlechner M, Bittner V, Wohlfahrt G, Loreto F, Hansel A - PLoS ONE (2011)

Ratios between the normalized emission rates Ek (t)                            varying over the time.Different panels indicate ratios of                                m/z = 83.085/m/z = 81.070                            (a) and m/z 143.107/m/z 81.070 (b)                            emitted after cutting leaves of Dactlylis glomerata                            (red lines) and of Populus alba (dark red lines) or                            after exposing to light to dark transition leaves of Dactlylis                                glomerata (blue lines) and of Populus alba                            (dark blue lines).
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3102719&req=5

pone-0020419-g007: Ratios between the normalized emission rates Ek (t) varying over the time.Different panels indicate ratios of m/z = 83.085/m/z = 81.070 (a) and m/z 143.107/m/z 81.070 (b) emitted after cutting leaves of Dactlylis glomerata (red lines) and of Populus alba (dark red lines) or after exposing to light to dark transition leaves of Dactlylis glomerata (blue lines) and of Populus alba (dark blue lines).
Mentions: In vivo information on the enzymatic activity leading to GLVs production cannot be provided according to Michealis-Menten model due to difficult estimation of substrate availability. This is the consequence of the continuous conversion of enzymatic products into further substrates which occurs once the cascade of multi-step enzymatic reaction (catalyzed by LOX, HPL, ADH and AD) has been initiated. However, by exploiting PTR-TOF highly resolved GLVs analysis, it may be possible to indirectly analyze differences in the activation of the lipoxygenase pathway by following the rate of conversion over the time between ratios of protonated ions. In particular the time course of the ratios between m/z = 83.085/81.070 (hexenols + hexanal/hexenals) and between m/z = 143.107/81.070 (hexenyl acetates/hexenals) may provide information about the speed of conversion of the classes of GLVs. We performed this analysis on GLVs emitted after cutting and after transition from light to dark transition by D. glomerata and P. alba leaves (Fig. 7 a,b). Our results show that wounding induces a differential production of the main GLVs over the time with respect to light-dark transition in both plant species. The instantaneous oxidation of linoleic and α-linolenic acids occurring when wounded cellular membranes are exposed to the air contact efficiently catalyzed the first step of the lipoxygenase reactions leading to the production of m/z = 81.070 (hexanal/hexenals) that is slowly converted to m/z = 83.085 (hexenols) and then to m/z = 143.107 (hexenyl acetates); differently the condition created by sudden darkening induces a production of both m/z = 81.070 than m/z = 83.085 (or m/z = 143.107) with similar time-courses.

Bottom Line: In the strong isoprene-emitter Populus alba, light-dependent isoprene emission was sustained and even enhanced for hours after photosynthesis inhibition due to leaf cutting.Thus isoprene emission can uncouple from photosynthesis and may occur even after cutting leaves or branches, e.g., by agricultural practices or because of abiotic and biotic stresses.This observation may have important implications for assessments of isoprene sources and budget in the atmosphere, and consequences for tropospheric chemistry.

View Article: PubMed Central - PubMed

Affiliation: Ionicon Analytik G.m.b.H., Innsbruck, Austria.

ABSTRACT
Proton transfer reaction-time of flight (PTR-TOF) mass spectrometry was used to improve detection of biogenic volatiles organic compounds (BVOCs) induced by leaf wounding and darkening. PTR-TOF measurements unambiguously captured the kinetic of the large emissions of green leaf volatiles (GLVs) and acetaldehyde after wounding and darkening. GLVs emission correlated with the extent of wounding, thus confirming to be an excellent indicator of mechanical damage. Transient emissions of methanol, C5 compounds and isoprene from plant species that do not emit isoprene constitutively were also detected after wounding. In the strong isoprene-emitter Populus alba, light-dependent isoprene emission was sustained and even enhanced for hours after photosynthesis inhibition due to leaf cutting. Thus isoprene emission can uncouple from photosynthesis and may occur even after cutting leaves or branches, e.g., by agricultural practices or because of abiotic and biotic stresses. This observation may have important implications for assessments of isoprene sources and budget in the atmosphere, and consequences for tropospheric chemistry.

Show MeSH
Related in: MedlinePlus