|
|
||||||||
|
First published online July 10, 2003; 10.1104/pp.103.022939 Plant Physiology 132:2144-2151 (2003) © 2003 American Society of Plant Biologists Changes in the Redox Potential of Primary and Secondary Electron-Accepting Quinones in Photosystem II Confer Increased Resistance to Photoinhibition in Low-Temperature-Acclimated Arabidopsis1Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, Umeå S901 87, Sweden (P.V.S., V.H., G.O.); and Biology Department, University of Western Ontario, London, Ontario, Canada N6A 5B7 (A.G.I., N.P.A.H.)
Exposure of control (non-hardened) Arabidopsis leaves for 2 h at high irradiance at 5°C resulted in a 55% decrease in photosystem II (PSII) photochemical efficiency as indicated by Fv/Fm. In contrast, cold-acclimated leaves exposed to the same conditions showed only a 22% decrease in Fv/Fm. Thermoluminescence was used to assess the possible role(s) of PSII recombination events in this differential resistance to photoinhibition. Thermoluminescence measurements of PSII revealed that S2QA- recombination was shifted to higher temperatures, whereas the characteristic temperature of the S2QB- recombination was shifted to lower temperatures in cold-acclimated plants. These shifts in recombination temperatures indicate higher activation energy for the S2QA- redox pair and lower activation energy for the S2QB- redox pair. This results in an increase in the free-energy gap between P680+QA- and P680+Pheo- and a narrowing of the free energy gap between primary and secondary electron-accepting quinones in PSII electron acceptors. We propose that these effects result in an increased population of reduced primary electron-accepting quinone in PSII, facilitating non-radiative P680+QA- radical pair recombination. Enhanced reaction center quenching was confirmed using in vivo chlorophyll fluorescence-quenching analysis. The enhanced dissipation of excess light energy within the reaction center of PSII, in part, accounts for the observed increase in resistance to high-light stress in cold-acclimated Arabidopsis plants.
1 This work was supported by the Swedish Foundation for International Cooperation in Research and Higher Education, by the Swedish Research Council, and by the Natural Science and Engineering Research Council of Canada. * Corresponding author; e-mail gunnar.oquist{at}plantphys.umu.se; fax 46907866676. Received March 4, 2003; returned for revision March 9, 2003; accepted April 29, 2003. This article has been cited by other articles:
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| ASPB Publications | PLANT PHYSIOLOGY® | THE PLANT CELL | |
|---|---|---|---|