Xylem-transported glucose as an additional carbon source for leaf isoprene formation in Quercus robur

Authors

  • Jürgen Kreuzwieser,

    1. Institut für Forstbotanik und Baumphysiologie, Professur für Baumphysiologie; Albert-Ludwigs-Universität Freiburg, Georges-Köhler-Allee Geb. 053/054, D–79110 Freiburg i. Br., Germany;
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  • Martin Graus,

    1. Institut für Ionenphysik; Leopold-Franzens-Universität Innsbruck, Technikerstrasse 25, A–6020 Innsbruck, Austria;
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  • Armin Wisthaler,

    1. Institut für Ionenphysik; Leopold-Franzens-Universität Innsbruck, Technikerstrasse 25, A–6020 Innsbruck, Austria;
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  • Armin Hansel,

    1. Institut für Ionenphysik; Leopold-Franzens-Universität Innsbruck, Technikerstrasse 25, A–6020 Innsbruck, Austria;
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  • Heinz Rennenberg,

    1. Institut für Forstbotanik und Baumphysiologie, Professur für Baumphysiologie; Albert-Ludwigs-Universität Freiburg, Georges-Köhler-Allee Geb. 053/054, D–79110 Freiburg i. Br., Germany;
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  • Jörg-Peter Schnitzler

    Corresponding author
    1. Institut für Meteorologie und Klimaforschung, Bereich Atmosphärische Umweltforschung (IMK-IFU); Forschungszentrum Karlsruhe GmbH, Kreuzeckbahnstr. 19, D–82467 Garmisch-Partenkirchen, Germany
      Author for correspondence:Jörg-Peter Schnitzler Tel: +49 8821183 131 Fax: +49 882173573 Email: joerg-peter.schnitzler@imk.fzk.de
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  • The work is dedicated to the memory of Wolfgang Zimmer, passed away on the 14th August 2002.

Author for correspondence:Jörg-Peter Schnitzler Tel: +49 8821183 131 Fax: +49 882173573 Email: joerg-peter.schnitzler@imk.fzk.de

Summary

  • • In order to test whether xylem-transported carbohydrates are a potential source for isoprene biosynthesis, [U- 13 C]-labelled α- d -glucose was fed via cut ends of stems into the xylem of Quercus robur seedlings and the incorporation of 13 C into isoprene emitted was studied. Emission of 13 C-labelled isoprene was monitored in real time by proton-transfer-reaction mass spectrometry (PTR-MS).
  • • A rapid incorporation of 13 C from xylem-fed glucose into single (mass 70) and double (mass 71) 13 C-labelled isoprene molecules was observed after a lag phase of approx. 5–10 min. This incorporation was temperature dependent and was highest (up to 13% 13 C of total carbon emitted as isoprene) at the temperature optimum of isoprene emission (40–42°C), when net assimilation was strongly reduced.
  • • Fast dark-to-light transitions led to a strong single or double 13 C-labelling of isoprene from xylem-fed [U-13C]glucose. During a period of 10–15 min up to 86% of all isoprene molecules became single or double 13 C-labelled, resulting in a 13 C-portion of up to 27% of total carbon emitted as isoprene.
  • • The results provide evidence that xylem-transported glucose or its degradation products can potentially be used as additional precursors for isoprene biosynthesis and that this carbon source becomes more important under conditions of limited photosynthesis.

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