Journal Article

Potential Errors in Electron Transport Rates Calculated from Chlorophyll Fluorescence as Revealed by a Multilayer Leaf Model

John R. Evans

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 50, issue 4, pages 698-706
Published in print April 2009 | ISSN: 0032-0781
Published online March 2009 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcp041
Potential Errors in Electron Transport Rates Calculated from Chlorophyll Fluorescence as Revealed by a Multilayer Leaf Model

More Like This

Show all results sharing these subjects:

  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

GO

Show Summary Details

Preview

Increasingly, photosynthetic electron transport rate is being calculated from chlorophyll fluorescence measure-ments. The fluorescence signal is a complex mixture of contributions from different depths within the mesophyll. One condition required for electron transport calculated from fluorescence to represent the rate accurately is that the ratio of photosynthetic capacity to light absorbed be constant throughout the leaf. In order to explore the fluorescence properties of leaves where this assumption is not true, a new approximation for φPSII is used to generate Fm and Fs values throughout the leaf. Fs is assumed to be proportional to the amount of light absorbed from the fluorescence measuring beam and constant, i.e. indep-endent of the actinic irradiance or CO2 concentration. This assumption is validated by measurements from Eucalyptus maculata, Flaveria bidentis and Triticum aestivum, with two different types of fluorometer, where irradiance or CO2 response curves were measured with normal or inverted leaf orientations. The new approach enables fluorescence values to be generated at each layer in a multilayer model. Two applications using this approach are presented. First, the model is used to show that when quantum yield varies through a leaf, then fluorescence will lead to an incorrect estimate of electron transport rate. Secondly, since chlorophyll fluorescence is also used to calculate the CO2 concentration at the sites of carboxyla-tion within chloroplasts, Cc, the model is also used to show that Cc may vary with depth. Significant variation in Cc through the mesophyll could lead to an apparent dependence of internal conductance on irradiance or CO2.

Keywords: Chloroplast; Internal conductance; Leaf anatomy; Light profiles; Mesophyll conductance; Rubisco

Journal Article.  5022 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

Full text: subscription required

How to subscribe Recommend to my Librarian

Users without a subscription are not able to see the full content. Please, subscribe or login to access all content.