PHloem transport: Cellular pathways and molecular trafficking

Robert Turgeon*, Shmuel Wolf

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

360 Scopus citations


The phloem transports nutrients, defensive compounds, and informational signals throughout vascular plants. Sampling the complex components of mobile phloem sap is difficult because of the damage incurred when the pressurized sieve tubes are breached. In this review we discuss sampling methods, the artifacts that can be introduced by different sampling procedures, the intricate pathways by which materials enter and exit the phloem, and the major types of compounds transported. Loading and unloading patterns are largely determined by the conductivity and number of plasmodesmata and the position-dependent function of solute-specific, plasma membrane transport proteins. Recent evidence indicates that mobile proteins and RNA are part of the plant's longdistance communication signaling system. Evidence also exists for the directed transport and sorting of macromolecules as they pass through plasmodesmata. A future challenge is to dissect the molecular and cellular aspects of long-distance macromolecular trafficking in the signal transduction pathways of the whole plant.

Original languageAmerican English
Pages (from-to)207-221
Number of pages15
JournalAnnual Review of Plant Biology
StatePublished - Jun 2009


  • Apoplast
  • Companion cell
  • Phloem loading
  • Plasmodesmata
  • Sieve element
  • Symplast


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