Article

Planta

, Volume 205, Issue 1, pp 132-139

First online:

The kinetics of sucrose concentration in the phloem of individual vascular bundles of the Ricinus communis seedling measured by nuclear magnetic resonance microimaging

  • Jutta VerschtAffiliated withPflanzenphysiologie, Universität Bayreuth, D-95440 Bayreuth, Germany
  • , Bernhard KaluscheAffiliated withExperimentelle Physik V, Universität Würzburg, D-97074 Würzburg, Germany
  • , Jutta KöhlerAffiliated withPflanzenphysiologie, Universität Bayreuth, D-95440 Bayreuth, Germany
  • , Walter KöckenbergerAffiliated withPflanzenphysiologie, Universität Bayreuth, D-95440 Bayreuth, Germany
  • , Alexander MetzlerAffiliated withFachbereich Biologie/Chemie, Universität Bremen, D-28334 Bremen, Germany
  • , Axel HaaseAffiliated withExperimentelle Physik V, Universität Würzburg, D-97074 Würzburg, Germany
  • , Ewald KomorAffiliated withPflanzenphysiologie, Universität Bayreuth, D-95440 Bayreuth, Germany

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Abstract.

The sucrose concentration was measured at 70-min intervals in the phloem of individual bundles of the hypocotyl of Ricinus seedlings by 1H nuclear magnetic resonance (NMR) spectroscopic imaging. The sucrose concentration stayed fairly constant in all bundles for more than 7 h if the cotyledons were embedded in the endosperm or excised and incubated in 100 mM sucrose. If, however, the sucrose solution was replaced by sucrose-free buffer solution, the sucrose levels in the phloem decreased with a kinetic depending on the seedling: in some cases there was a smooth decline, in some a decline followed by a slight recovery and in some cases a clear-cut oscillation. The sucrose concentration was often not identical in the phloem of the individual bundles. The oscillations were larger in the phloem at the apex of the hypocotyl than in the phloem at the base of the hypocotyl. Cutting the petiole of one cotyledon led to a decrease in sucrose not only in the four bundles directly connected to the severed petiole but in all eight bundles of the hypocotyl. Cutting the petiole and dividing the vascular ring at the cotyledonary node and at the root crown did not prevent the decline of sucrose in all eight bundles. Therefore, a functional equilibration of translocated solutes between the eight bundles may occur within the 1-h measuring interval by radial diffusion through the parenchyma of the hypocotyl.

Key words: Node (vasculature) Phloem Ricinus (phloem sucrose) Sieve tube Sucrose deprivation