Role of the oxidized secondary acceptor Q B of Photosystem II in the delayed 'afterglow' chlorophyll luminescence

Jean Marc Ducruet, Miruna Roman, Jose Maria Ortega, Tibor Janda

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

Leaf discs of dark-adapted tobacco plants were excited by 2 flashes and kept in darkness at 20°C for various time periods, then thermoluminescence emission was recorded without freezing the sample. The B band at 30°C decreased with a half-time t 1/2~1 min and the AG band at 45°C with a t 1/2~5 min. This corresponds to the decay kinetics of S 2/3 in PS II centres in the state S2/3 Q B - (B band) or S2/3 Q B . Assuming that the 45°C band is an 'afterglow' emission originating from those centres with an oxidized Q B on which an electron is back-transferred from stroma reductants through a pathway induced by warming, the theoretical ratio of the B and AG band was compared to that measured experimentally. After 2 or 3 flashes producing mainly S3, the intensity of AG band encompassed several fold that of the B band, because recombining S3 recreated S 2 Q B AG-emitting centres. In order to confirm that the AG band is governed by the heat-induced activation of a dark Q B -reducing pathway rather than by PS II charge recombination, the AG emission was characterized in triazine-resistant Chenopodium album weed biotypes. In these mutants where the Q B pocket is altered, the B band is strongly downshifted to 18°C, compared to 32°C in the wild type, whereas the AG band is only downshifted by 3 or 4°C, demonstrating that S2/3 Q B - is not the limiting step of the AG emission.

Original languageEnglish
Pages (from-to)161-166
Number of pages6
JournalPhotosynthesis research
Volume84
Issue number1-3
DOIs
Publication statusPublished - Jun 1 2005

Keywords

  • Chlororespiration
  • Cyclic electron flow
  • Photosystem II
  • Thermoluminescence

ASJC Scopus subject areas

  • Biochemistry
  • Plant Science
  • Cell Biology

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