, Volume 201, Issue 2, pp 195-201

First online:

Symplasmic connections between sieve element and companion cell in the stem phloem ofVicia faba L. have a molecular exclusion limit of at least 10 kDa

  • Ronald KempersAffiliated withTransport Physiology Research Group, Department of Plant Ecology and Evolutionary Biology, Utrecht University Email author 
  • , Aart J. E. van BelAffiliated withBotanisches Institut 1, Justus-Liebig University

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High-molecular-weight fluorochromes were intracellularly injected into a sieve element of the fascicular stem phloem ofVicia faba L., using a modified membrane-potential-recording pressure probe. After stabilization of the membrane potential following microelectrode impalement, either LYCH (Lucifer Yellow CH), 4.4-kDa FITC-dextran (fluoresceinisothiocyanate-dextran) conjugate, or 3-kDa, 10-kDa or 40-kDa LYCH-dextran conjugate was microinjected into the sieve element. Longitudinal fluorochrome movement across the sieve plates and lateral displacement to the companion cells was detected with all the probes except the 40-kDa conjugate. This indicates that the molecular exclusion limit of the pore/plasmodesma units between a sieve element and a companion cell in the fascicular stem phloem ofVicia faba lies between 10 kDa and 40 kDa.

Key words

Fluorescent dextran Intracellular microinjection Molecular exclusion limit Pore/plasmodesma unit Sieve element/companion cell complex Vicia