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, T. 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 2005

Fingerprint

Triazines
Thermoluminescence
Photosystem II Protein Complex
Tobacco
luminescence
Reducing Agents
Chlorophyll
Luminescence
Freezing
photosystem II
Chenopodium album
Chemical activation
chlorophyll
Kinetics
Electrons
Darkness
Genetic Recombination
Hot Temperature
reducing agents
triazines

Keywords

  • Chlororespiration
  • Cyclic electron flow
  • Photosystem II
  • Thermoluminescence

ASJC Scopus subject areas

  • Plant Science

Cite this

Role of the oxidized secondary acceptor Q B of Photosystem II in the delayed 'afterglow' chlorophyll luminescence. / Ducruet, Jean Marc; Roman, Miruna; Ortega, Jose Maria; Janda, T.

In: Photosynthesis Research, Vol. 84, No. 1-3, 06.2005, p. 161-166.

Research output: Contribution to journalArticle

Ducruet, Jean Marc ; Roman, Miruna ; Ortega, Jose Maria ; Janda, T. / Role of the oxidized secondary acceptor Q B of Photosystem II in the delayed 'afterglow' chlorophyll luminescence. In: Photosynthesis Research. 2005 ; Vol. 84, No. 1-3. pp. 161-166.
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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.",
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AB - 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.

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