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Biogenic volatile organic compound and respiratory CO2 emissions after 13C-labeling: online tracing of C translocation dynamics in poplar plants.

Ghirardo A, Gutknecht J, Zimmer I, Brüggemann N, Schnitzler JP - PLoS ONE (2011)

Bottom Line: The daily C loss as BVOC ranged between 1.6% in mature leaves and 7.0% in young leaves.Non-isoprene BVOC accounted under light conditions for half of the BVOC C loss in young leaves and one-third in mature leaves.We quantified the plants' C loss as respiratory CO(2) and BVOC emissions, allowing in tandem with metabolic analysis to deepen our understanding of ecosystem C flux.

View Article: PubMed Central - PubMed

Affiliation: Karlsruhe Institute of Technology, Institute for Meteorology and Climate Research, Garmisch-Partenkirchen, Germany.

ABSTRACT

Background: Globally plants are the primary sink of atmospheric CO(2), but are also the major contributor of a large spectrum of atmospheric reactive hydrocarbons such as terpenes (e.g. isoprene) and other biogenic volatile organic compounds (BVOC). The prediction of plant carbon (C) uptake and atmospheric oxidation capacity are crucial to define the trajectory and consequences of global environmental changes. To achieve this, the biosynthesis of BVOC and the dynamics of C allocation and translocation in both plants and ecosystems are important.

Methodology: We combined tunable diode laser absorption spectrometry (TDLAS) and proton transfer reaction mass spectrometry (PTR-MS) for studying isoprene biosynthesis and following C fluxes within grey poplar (Populus x canescens) saplings. This was achieved by feeding either (13)CO(2) to leaves or (13)C-glucose to shoots via xylem uptake. The translocation of (13)CO(2) from the source to other plant parts could be traced by (13)C-labeled isoprene and respiratory (13)CO(2) emission.

Principal finding: In intact plants, assimilated (13)CO(2) was rapidly translocated via the phloem to the roots within 1 hour, with an average phloem transport velocity of 20.3±2.5 cm h(-1). (13)C label was stored in the roots and partially reallocated to the plants' apical part one day after labeling, particularly in the absence of photosynthesis. The daily C loss as BVOC ranged between 1.6% in mature leaves and 7.0% in young leaves. Non-isoprene BVOC accounted under light conditions for half of the BVOC C loss in young leaves and one-third in mature leaves. The C loss as isoprene originated mainly (76-78%) from recently fixed CO(2), to a minor extent from xylem-transported sugars (7-11%) and from photosynthetic intermediates with slower turnover rates (8-11%).

Conclusion: We quantified the plants' C loss as respiratory CO(2) and BVOC emissions, allowing in tandem with metabolic analysis to deepen our understanding of ecosystem C flux.

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Concentration of the isoprene precursor DMADP and incorporation of 13C in DMADP molecules in different plant parts of intact poplar plants and detached shoots.DMADP content (grey bars) and 13C-incorporation into DMADP (black bars) in (A) apex, mature leaf, labeled leaf and root of intact plants labeled with 13CO2, in (B) apex and leaves of shoots labeled with 13CO2, and in (C) labeled with 13Glc. Leaf DMADP content and relative 13C-abundance (% of 13C in total DMADP carbon) was assayed as described by Ghirardo et al. [10]. Data represent the mean of 3 experiments ± s.d. (n.s.: no significant 13C-enrichment).
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pone-0017393-g009: Concentration of the isoprene precursor DMADP and incorporation of 13C in DMADP molecules in different plant parts of intact poplar plants and detached shoots.DMADP content (grey bars) and 13C-incorporation into DMADP (black bars) in (A) apex, mature leaf, labeled leaf and root of intact plants labeled with 13CO2, in (B) apex and leaves of shoots labeled with 13CO2, and in (C) labeled with 13Glc. Leaf DMADP content and relative 13C-abundance (% of 13C in total DMADP carbon) was assayed as described by Ghirardo et al. [10]. Data represent the mean of 3 experiments ± s.d. (n.s.: no significant 13C-enrichment).

Mentions: Our dataset documented an age-dependent accumulation pattern of the isoprene precursor DMADP (Fig. 9), concomitant with an age-dependent emission rate of isoprene (Fig. 6, 10E). Young developing leaves (leaves # 1–4) reached emission levels of only 15–30% compared to emission rates of mature leaves (leaves # 7–10; Fig. 6A, B). The isoprene emission slightly decreased with leaf age or lower position in the plant canopy (leaves # 14–16; Fig 6C). The leaf position (i.e. age) effect was also visible over the duration of the experiment, with an increase of isoprene emission in young leaves and decrease in mature leaves (Fig. 6A, B, C). In experiments with detached shoots, lower DMADP pools were accompanied by lower isoprene emission rates (Fig. 7 and 9). We also observed a very low, but still detectable emission of isoprene from the root system (Fig. 6C), which might have resulted from chemical conversion of DMADP into isoprene, since no isoprene synthase activity was detectable in root protein extracts (data not shown).


Biogenic volatile organic compound and respiratory CO2 emissions after 13C-labeling: online tracing of C translocation dynamics in poplar plants.

Ghirardo A, Gutknecht J, Zimmer I, Brüggemann N, Schnitzler JP - PLoS ONE (2011)

Concentration of the isoprene precursor DMADP and incorporation of 13C in DMADP molecules in different plant parts of intact poplar plants and detached shoots.DMADP content (grey bars) and 13C-incorporation into DMADP (black bars) in (A) apex, mature leaf, labeled leaf and root of intact plants labeled with 13CO2, in (B) apex and leaves of shoots labeled with 13CO2, and in (C) labeled with 13Glc. Leaf DMADP content and relative 13C-abundance (% of 13C in total DMADP carbon) was assayed as described by Ghirardo et al. [10]. Data represent the mean of 3 experiments ± s.d. (n.s.: no significant 13C-enrichment).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3046154&req=5

pone-0017393-g009: Concentration of the isoprene precursor DMADP and incorporation of 13C in DMADP molecules in different plant parts of intact poplar plants and detached shoots.DMADP content (grey bars) and 13C-incorporation into DMADP (black bars) in (A) apex, mature leaf, labeled leaf and root of intact plants labeled with 13CO2, in (B) apex and leaves of shoots labeled with 13CO2, and in (C) labeled with 13Glc. Leaf DMADP content and relative 13C-abundance (% of 13C in total DMADP carbon) was assayed as described by Ghirardo et al. [10]. Data represent the mean of 3 experiments ± s.d. (n.s.: no significant 13C-enrichment).
Mentions: Our dataset documented an age-dependent accumulation pattern of the isoprene precursor DMADP (Fig. 9), concomitant with an age-dependent emission rate of isoprene (Fig. 6, 10E). Young developing leaves (leaves # 1–4) reached emission levels of only 15–30% compared to emission rates of mature leaves (leaves # 7–10; Fig. 6A, B). The isoprene emission slightly decreased with leaf age or lower position in the plant canopy (leaves # 14–16; Fig 6C). The leaf position (i.e. age) effect was also visible over the duration of the experiment, with an increase of isoprene emission in young leaves and decrease in mature leaves (Fig. 6A, B, C). In experiments with detached shoots, lower DMADP pools were accompanied by lower isoprene emission rates (Fig. 7 and 9). We also observed a very low, but still detectable emission of isoprene from the root system (Fig. 6C), which might have resulted from chemical conversion of DMADP into isoprene, since no isoprene synthase activity was detectable in root protein extracts (data not shown).

Bottom Line: The daily C loss as BVOC ranged between 1.6% in mature leaves and 7.0% in young leaves.Non-isoprene BVOC accounted under light conditions for half of the BVOC C loss in young leaves and one-third in mature leaves.We quantified the plants' C loss as respiratory CO(2) and BVOC emissions, allowing in tandem with metabolic analysis to deepen our understanding of ecosystem C flux.

View Article: PubMed Central - PubMed

Affiliation: Karlsruhe Institute of Technology, Institute for Meteorology and Climate Research, Garmisch-Partenkirchen, Germany.

ABSTRACT

Background: Globally plants are the primary sink of atmospheric CO(2), but are also the major contributor of a large spectrum of atmospheric reactive hydrocarbons such as terpenes (e.g. isoprene) and other biogenic volatile organic compounds (BVOC). The prediction of plant carbon (C) uptake and atmospheric oxidation capacity are crucial to define the trajectory and consequences of global environmental changes. To achieve this, the biosynthesis of BVOC and the dynamics of C allocation and translocation in both plants and ecosystems are important.

Methodology: We combined tunable diode laser absorption spectrometry (TDLAS) and proton transfer reaction mass spectrometry (PTR-MS) for studying isoprene biosynthesis and following C fluxes within grey poplar (Populus x canescens) saplings. This was achieved by feeding either (13)CO(2) to leaves or (13)C-glucose to shoots via xylem uptake. The translocation of (13)CO(2) from the source to other plant parts could be traced by (13)C-labeled isoprene and respiratory (13)CO(2) emission.

Principal finding: In intact plants, assimilated (13)CO(2) was rapidly translocated via the phloem to the roots within 1 hour, with an average phloem transport velocity of 20.3±2.5 cm h(-1). (13)C label was stored in the roots and partially reallocated to the plants' apical part one day after labeling, particularly in the absence of photosynthesis. The daily C loss as BVOC ranged between 1.6% in mature leaves and 7.0% in young leaves. Non-isoprene BVOC accounted under light conditions for half of the BVOC C loss in young leaves and one-third in mature leaves. The C loss as isoprene originated mainly (76-78%) from recently fixed CO(2), to a minor extent from xylem-transported sugars (7-11%) and from photosynthetic intermediates with slower turnover rates (8-11%).

Conclusion: We quantified the plants' C loss as respiratory CO(2) and BVOC emissions, allowing in tandem with metabolic analysis to deepen our understanding of ecosystem C flux.

Show MeSH
Related in: MedlinePlus