Skip Navigation



Plant and Cell Physiology Advance Access published online on October 15, 2007
Plant and Cell Physiology, doi:10.1093/pcp/pcm129
This Article
Right arrow Advance Access manuscript (PDF)
Right arrow All Versions of this Article:
48/11/1575    most recent
pcm129v1
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 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 Laisk, A.
Right arrow Articles by Scheibe, R.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Laisk, A.
Right arrow Articles by Scheibe, R.
Agricola
Right arrow Articles by Laisk, A.
Right arrow Articles by Scheibe, R.
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 e-mail: journals.permissions@oxfordjournals.org

Rates and Roles of Cyclic and Alternative Electron Flow in Potato Leaves

Agu Laisk*, Hillar Eichelmann, Vello Oja, Eero Talts and Renate Scheibe1

Tartu ülikooli Molekulaar- ja Rakubioloogia Instituut, Riia tn. 23, Tartu, 51010, Estonia
1Pflanzenphysiologie, FB5, Universität Osnabrück, 49069 Osnabrück, Germany

* Corresponding author; e-mail alaisk{at}ut.ee, fax 372 736 6021


  Abstract

Measurements of 810 nm transmittance changes in leaves, simultaneously with Chl fluorescence, CO2 uptake and O2 evolution, were carried out on potato (Solanum tuberosum L.) leaves with altered expression of plastidic NADP-dependent malate dehydrogenase. Electron transport rates were calculated, JC from the CO2 uptake rate considering RuBP carboxylation and oxygenation, JO from the O2 evolution rate, JF from Chl fluorescence parameters and JI from the post-illumination re-reduction speed of PSI donors. In the absence of external O2, JO equaled (1.005 ±0.003) JC, independent of the transgenic treatment, light intensity and CO2 concentration. This showed nitrite and oxaloacetate reduction rates were very slow. The Mehler type O2 reduction was evaluated from the rate of electron accumulation at PSI after O2 concentration was decreased from 210 to 20 mmol mol-1, and resulted in less than 1% of the linear flow. JF and JI did not differ from JC while photosynthesis was light-limited, but considerably exceeded JC at saturating light. Then typically JF = 1.2 JC and JI = 1.3 JC, and JF –JC and JI –JC little depended on CO2 and O2 concentrations. The results showed, the alternative and cyclic electron flow necessary to compensate variations in the ATP/NADPH ratio were only a few per cent of the linear flow. The data do not support the requirement of 14H+/3ATP by the chloroplast ATP synthase. We suggest that the fast PSI cyclic electron flow JI – JC, as well as the fast JF – JC are energy-dissipating cycles around PSI and PSII at light saturation.

Keywords: Leaf - Cyclic - Alternative - Electron transport

(Received July 13, 2007; Accepted October 3, 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.