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Bundle sheath chloroplast volume can house sufficient Rubisco to avoid limiting C4 photosynthesis during chilling.

Authors
  • Pignon, Charles P1
  • Lundgren, Marjorie R2, 3, 4
  • Osborne, Colin P5
  • Long, Stephen P1, 4
  • 1 University of Illinois, Carl R. Woese Institute for Genomic Biology and Departments of Crop Sciences and of Plant Biology, Urbana, IL, USA.
  • 2 Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, USA.
  • 3 Arnold Arboretum, Harvard University, Boston, USA.
  • 4 Lancaster Environment Centre, Lancaster University, Lancaster, UK.
  • 5 Department of Animal and Plant Sciences, Alfred Denny Building, University of Sheffield, Sheffield, UK.
Type
Published Article
Journal
Journal of Experimental Botany
Publisher
Oxford University Press
Publication Date
Jan 01, 2019
Volume
70
Issue
1
Pages
357–365
Identifiers
DOI: 10.1093/jxb/ery345
PMID: 30407578
Source
Medline
Language
English
License
Unknown

Abstract

C4 leaves confine Rubisco to bundle sheath cells. Thus, the size of bundle sheath compartments and the total volume of chloroplasts within them limit the space available for Rubisco. Rubisco activity limits photosynthesis at low temperatures. C3 plants counter this limitation by increasing leaf Rubisco content, yet few C4 species do the same. Because C3 plants usually outperform C4 plants in chilling environments, it has been suggested that there is insufficient chloroplast volume available in the bundle sheath of C4 leaves to allow such an increase in Rubisco at low temperatures. We investigated this potential limitation by measuring bundle sheath and mesophyll compartment volumes and chloroplast contents, as well as leaf thickness and inter-veinal distance, in three C4 Andropogoneae grasses: two crops (Zea mays and Saccharum officinarum) and a wild, chilling-tolerant grass (Miscanthus × giganteus). A wild C4 Paniceae grass (Alloteropsis semialata) was also included. Despite significant structural differences between species, there was no evidence of increased bundle sheath chloroplast volume per leaf area available to the chilling-tolerant species, relative to the chilling-sensitive ones. Maximal theoretical photosynthetic capacity of the leaf far exceeded the photosynthetic rates achieved even at low temperatures. C4 bundle sheath cells therefore have the chloroplast volume to house sufficient Rubisco to avoid limiting C4 photosynthesis during chilling.

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