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Phloem pp 55-72 | Cite as

Quantification of Leaf Phloem Anatomical Features with Microscopy

  • Jared J. Stewart
  • Onno Muller
  • Christopher M. Cohu
  • Barbara Demmig-Adams
  • William W. AdamsIIIEmail author
Protocol
Part of the Methods in Molecular Biology book series (MIMB, volume 2014)

Abstract

Measurements of vein density and foliar minor vein phloem cell numbers, minor vein phloem cell sizes, and transfer cell wall ingrowths provide quantitative proxies for the leaf’s capacities to load and export photosynthates. While overall infrastructural capacity for sugar loading and sugar export correlated positively and closely with photosynthetic capacity, the specific targets of the adjustment of minor vein organization varied with phloem-loading mechanism, plant life-cycle characteristics, and environmental growth conditions. Among apoplastic loaders, for which sugar loading into the phloem depends on cell membrane-spanning transport proteins, variation in minor vein density, phloem cell number, and level of cell wall ingrowth (when present) were consistently associated with photosynthetic capacity. Among active symplastic loaders, for which sugar loading into the phloem depends on cytosolic enzymes, variation in vein density and phloem cell size were consistently associated with photosynthetic capacity. All of these anatomical features were also subject to acclimatory adjustment depending on species and environmental conditions, with increased levels of these features supporting higher rates of photosynthesis. We present a procedure for the preparation of leaf tissue for minor vein analysis, using both light and transmission electron microscopy, that facilitates quantification of not only phloem features but also xylem features that provide proxies for foliar water import capacity.

Key words

Phloem anatomy Photosynthesis Sugar transport Sieve element Transport capacity 

Abbreviations

CA

Cross-sectional area of cells per minor vein

CC

Companion cell

CN

Cell number per minor vein

EM

Electron microscopy

PC

Phloem parenchyma cell

SE

Sieve element

TE

Tracheary element

VD

Minor vein density

VP

Vascular parenchyma

XP

Xylem parenchyma

Notes

Acknowledgments

We thank Dr. Thomas Giddings, Dr. Véronique Amiard, and Prof. Robert Turgeon for instruction, advice, and valuable discussion. This work was supported by the National Science Foundation (Award Numbers IOS-0841546, DEB-0122236, and IBN-0235351) and the University of Colorado at Boulder.

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Copyright information

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

Authors and Affiliations

  • Jared J. Stewart
    • 1
  • Onno Muller
    • 2
  • Christopher M. Cohu
    • 3
  • Barbara Demmig-Adams
    • 1
  • William W. AdamsIII
    • 1
    Email author
  1. 1.Department of Ecology and Evolutionary BiologyUniversity of ColoradoBoulderUSA
  2. 2.Institue of Bio- and Geosciences, IBG-2: Plant SciencesForschungszentrum Jülich GmbHJülichGermany
  3. 3.Department of Environmental Sciences and TechnologyColorado Mesa UniversityGrand JunctionUSA

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