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Symplasmic Transport in Phloem Loading and Unloading

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Symplasmic Transport in Vascular Plants

Abstract

The coordinated distribution of carbohydrates between different plant organs takes place in the phloem. Understanding how carbohydrates are loaded into and unloaded from this long-distance transport system is essential for our understanding of carbon allocation in plants and the mechanism of phloem transport.

In this chapter, we present the current knowledge on how sugars move from the site of production in the leaf parenchyma towards the phloem and how they exit the phloem in sink organs and move to the sites of consumption or storage. The main focus lies on symplasmic transport through plasmodesmata, which is central to all questions of intercellular carbohydrate transport. Recent investigations in non-model plant species, especially the gymnosperms, provide a more comprehensive picture of phloem loading and unloading processes than ever before, but many questions regarding underlying mechanisms, evolution, pathway capacity, and regulation remain.

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Abbreviations

BSC:

Bundle sheath cell

CF:

Carboxyfluorescein

CC:

Companion cell

IC:

Intermediary cell

PD:

Plasmodesmata

SE:

Sieve element

SECCC:

Companion cell/sieve element complex

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  1. Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, Frederiksberg, C 1871, Copenhagen, Denmark

    Johannes Liesche Ph.D. & Alexander Schulz Ph.D.

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  1. Johannes Liesche Ph.D.
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  2. Alexander Schulz Ph.D.
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Correspondence to Johannes Liesche Ph.D. .

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  1. Dept. Plant Morphology and Development, University of Wrocław, Wrocław, Poland

    Katarzyna Sokołowska

  2. Dept. of Plant Molecular Ecophysiology Faculty of Botany, University of Warsaw, Warsaw, Poland

    Paweł Sowiński

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Liesche, J., Schulz, A. (2013). Symplasmic Transport in Phloem Loading and Unloading. In: Sokołowska, K., Sowiński, P. (eds) Symplasmic Transport in Vascular Plants. Springer, New York, NY. https://doi.org/10.1007/978-1-4614-7765-5_5

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