Skip Navigation


Plant and Cell Physiology Advance Access originally published online on November 20, 2007
Plant and Cell Physiology 2008 49(1):19-29; doi:10.1093/pcp/pcm160
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
49/1/19    most recent
pcm160v1
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrowRequest Permissions
Google Scholar
Right arrow Articles by Tazoe, Y.
Right arrow Articles by Terashima, I.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Tazoe, Y.
Right arrow Articles by Terashima, I.
Agricola
Right arrow Articles by Tazoe, Y.
Right arrow Articles by Terashima, I.
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?

© The Author 2007. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oxfordjournals.org

Relationships Between Quantum Yield for CO2 Assimilation, Activity of Key Enzymes and CO2 Leakiness in Amaranthus cruentus, a C4 Dicot, Grown in High or Low Light

Youshi Tazoe1,4,*, Yuko T. Hanba2, Tsuyoshi Furumoto3, Ko Noguchi1 and Ichiro Terashima1

1Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033 Japan
2Center for Bioresource Field Science, Kyoto Institute of Technology, Ukyo-ku, Kyoto, 616-8354 Japan
3Department of Biological Science, Graduate School of Science, Hiroshima University, Higashihiroshima, Hiroshima, 739-8526 Japan

*Corresponding author: E-mail, youshi.tazoe{at}anu.edu.au; Fax, +61-2-6125-4919.


  Abstract

In C4 photosynthesis, a part of CO2 fixed by phosphoenolpyruvate carboxylase (PEPC) leaks from the bundle-sheath cells. Because the CO2 leak wastes ATP consumed in the C4 cycle, the leak may decrease the efficiency of CO2 assimilation. To examine this possibility, we studied the light dependence of CO2 leakiness ({varphi}), estimated by the concurrent measurements of gas exchange and carbon isotope discrimination, initial activities of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) and pyruvate, orthophosphate dikinase (PPDK), the phosphorylation state of PEPC and the CO2 assimilation rate using leaves of Amaranthus cruentus (NAD-malic enzyme subtype, dicot) plants grown in high light (HL) and low light (LL). {varphi} was constant at photon flux densities (PFDs) >200 µmol m–2 s–1 and was around 0.3. At PFDs <150 µmol m–2 s–1, {varphi} increased markedly as PFD decreased. At 40 µmol m–2 s–1, {varphi} was 0.76 in HL and 0.55 in LL leaves, indicating that the efficiency of CO2 assimilation at low PFD was greater in LL leaves. The activities of Rubisco and PPDK, and the phosphorylated state of PEPC all decreased as PFD decreased. Theoretical calculations with a mathematical model clearly showed that the increase in {varphi} with decreasing PFD contributed to the decrease in the CO2 assimilation rate. It was also shown that the ‘conventional’ quantum yield of photosynthesis obtained by fitting the straight line to the light response curve of the CO2 assimilation rate at the low PFD region is seriously overestimated. Ecological implications of the increase in {varphi} in LL are discussed.

Keywords: Carbon isotope discrimination - Phosphoenolpyruvate carboxylase (PEPC) - Pyruvate, orthophosphate dikinase (PPDK) - Ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco)

Abbreviations: BS, bundle-sheath; DTT, dithiothreitol; HL, high light; LL, low light; ME, malic enzyme; PEP, phosphoenolpyruvate; PEPC, phosphoenolpyruvate carboxylase; PFD, photon flux density; PK, protein kinase; PPDK, pyruvate, orthophosphate dikinase; PVDF, polyvinylidenedifluoride; Rubisco, ribulose 1,5-bisphosphate carboxylase/oxygenase; RuBP, ribulose 1,5-bisphosphate.

4Present address: Research School of Biological Sciences, Australian National University, Canberra, Australian Capital Territory 2601, Australia.

(Received July 17, 2007; Accepted November 15, 2007)
Add to CiteULike CiteULike   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us    What's this?




Disclaimer:
Please note that abstracts for content published before 1996 were created through digital scanning and may therefore not exactly replicate the text of the original print issues. All efforts have been made to ensure accuracy, but the Publisher will not be held responsible for any remaining inaccuracies. If you require any further clarification, please contact our Customer Services Department.