Journal article
Phloem Ultrastructure and Pressure Flow: Sieve-Element-Occlusion-Related Agglomerations Do Not Affect Translocation[W]
The Plant cell, Vol.23(12), pp.4428-4445
12/2011
Handle:
https://hdl.handle.net/2376/109005
PMCID: PMC3269875
PMID: 22198148
Abstract
Several protocols and methods were developed to study the in vivo structure, ultrastructure, and physiology of sieve tubes. The ultrastructure of sieve tubes differs significantly from what has been shown so far. The impact on phloem function is discussed.
Since the first ultrastructural investigations of sieve tubes in the early 1960s, their structure has been a matter of debate. Because sieve tube structure defines frictional interactions in the tube system, the presence of P protein obstructions shown in many transmission electron micrographs led to a discussion about the mode of phloem transport. At present, it is generally agreed that P protein agglomerations are preparation artifacts due to injury, the lumen of sieve tubes is free of obstructions, and phloem flow is driven by an osmotically generated pressure differential according to Münch’s classical hypothesis. Here, we show that the phloem contains a distinctive network of protein filaments. Stable transgenic lines expressing
Arabidopsis thaliana
Sieve-Element-Occlusion-Related1 (SEOR1)–yellow fluorescent protein fusions show that At SEOR1 meshworks at the margins and clots in the lumen are a general feature of living sieve tubes. Live imaging of phloem flow and flow velocity measurements in individual tubes indicate that At SEOR1 agglomerations do not markedly affect or alter flow. A transmission electron microscopy preparation protocol has been generated showing sieve tube ultrastructure of unprecedented quality. A reconstruction of sieve tube ultrastructure served as basis for tube resistance calculations. The impact of agglomerations on phloem flow is discussed.
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Details
- Title
- Phloem Ultrastructure and Pressure Flow: Sieve-Element-Occlusion-Related Agglomerations Do Not Affect Translocation[W]
- Creators
- Daniel R Froelich - School of Biological Sciences, Washington State University, Pullman Washington 99164-4236Daniel L Mullendore - School of Biological Sciences, Washington State University, Pullman Washington 99164-4236Kåre H Jensen - Department of Physics, Technical University of Denmark, 2800 Kongens Lyngby, DenmarkTim J Ross-Elliott - School of Biological Sciences, Washington State University, Pullman Washington 99164-4236James A Anstead - College of Agricultural Sciences, Pennsylvania State University, Pennsylvania 16802Gary A Thompson - College of Agricultural Sciences, Pennsylvania State University, Pennsylvania 16802Hélène C Pélissier - School of Biological Sciences, Washington State University, Pullman Washington 99164-4236Michael Knoblauch - School of Biological Sciences, Washington State University, Pullman Washington 99164-4236
- Publication Details
- The Plant cell, Vol.23(12), pp.4428-4445
- Academic Unit
- Biological Sciences, School of
- Publisher
- American Society of Plant Biologists
- Identifiers
- 99900547348201842
- Language
- English
- Resource Type
- Journal article