Phloem pp 215-221 | Cite as

Quantification of Symplasmic Phloem Loading Capacity with Live-Cell Microscopy

  • Helle Juel Martens
  • Chen Gao
  • Johannes LiescheEmail author
Part of the Methods in Molecular Biology book series (MIMB, volume 2014)


Sugars produced by photosynthesis in leaves get transported to other organs in the phloem vascular tissue. Three general mechanisms have been proposed for the loading of sugars into the phloem. These differ in the involvement of active transport across the phloem cell’s membrane and their capacity for passive intercellular transport through plasmodesmata. This capacity for diffusion from the mesophyll into the phloem cells can be quantified by live-cell microscopy. Instead of sugar molecules, the movement of fluorescent tracers of similar size can be observed. In this chapter, a simple method is described that allows quantification of plasmodesmata-mediated intercellular diffusion across the mesophyll-bundle sheath interface and the bundle sheath-phloem cell interfaces. The fluorescent tracer carboxyfluorescein is loaded into intact leaves and its diffusion monitored with confocal microscopy after photobleaching of a bundle sheath cell.

Key words

Plasmodesmata Phloem loading Carbon allocation Live-cell microscopy Fluorescent tracer Photobleaching 


  1. 1.
    Liesche J, Patrick J (2017) An update on phloem transport: a simple bulk flow under complex regulation. F1000Res 6:2096CrossRefGoogle Scholar
  2. 2.
    Rennie EA, Turgeon R (2009) A comprehensive picture of phloem loading strategies. Proc Natl Acad Sci U S A 106:14162–14167CrossRefGoogle Scholar
  3. 3.
    Liesche J, Gao C, Binczycki P, Andersen SR, Rademaker H, Schulz A, Martens H (2019) Direct comparison of leaf plasmodesmatal structure and function in relation to phloem loading type. Plant Physiol 179(4):1768–1778CrossRefGoogle Scholar
  4. 4.
    Liesche J, Schulz A (2013) Modeling the parameters for plasmodesmal sugar filtering in active symplasmic phloem loaders. Front Plant Sci 4:207CrossRefGoogle Scholar
  5. 5.
    Liesche J, Schulz A (2012) Quantification of plant cell coupling with three-dimensional photoactivation microscopy. J Microsc 247:2–9CrossRefGoogle Scholar
  6. 6.
    Liesche J, Schulz A (2015) Quantification of plant cell coupling with live-cell microscopy. Methods Mol Biol 1217:137–148CrossRefGoogle Scholar
  7. 7.
    Liesche J, Schulz A (2012) In vivo quantification of cell coupling in plants with different phloem-loading strategies. Plant Physiol 159:355–365CrossRefGoogle Scholar
  8. 8.
    Schindelin J, Arganda-Carreras I, Frise E, Kaynig V, Longair M, Pietzsch T, Preibisch S, Rueden C, Saalfeld S, Schmid B, Tinevez JY, White DJ, Hartenstein V, Eliceiri K, Tomancak P, Cardona A (2012) Fiji: an open-source platform for biological-image analysis. Nat Methods 28:676–682CrossRefGoogle Scholar
  9. 9.
    Oparka KJ, Prior DAM (1992) Direct evidence for pressure-generated closure of plasmodesmata. Plant J 2:741–750CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2019

Authors and Affiliations

  • Helle Juel Martens
    • 1
  • Chen Gao
    • 2
  • Johannes Liesche
    • 2
    Email author
  1. 1.Department of Geosciences and Natural ResourcesUniversity of CopenhagenCopenhagenDenmark
  2. 2.College of Life SciencesNorthwest A&F UniversityYanglingChina

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