The role of light in formation of modified S2-state upon low pH-treatment of oxygen-evolving Photosystem II

Jian Ren Shen, Taka aki Ono, Yorinao Inoue

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2 Citations (Scopus)


An abnormal, structurally modified, kinetically stable S2-state has been reported to be induced when Photosystem II was treated with NaCl-EGTA (or EDTA) in the light or with pH in darkness, both are assumed to release functional Ca2+. In order to compare the mechanism of induction of modified S2-state between the two treatments, effects of illumination during or before low pH-treatment on formation of the abnormal S2-state were investigated by means of thermoluminescence measurements and low temperature EPR spectroscopy. Following results have been obtained: Flash illumination during low pH-treatment did not practically induce the abnormal S2-state, whereas preflash illumination given immediately before low pH-treatment efficiently induced the abnormal S2-state, and its amplitude showed a period-four oscillation on varying the preflash number with maxima at the second and sixth flashes. The abnormal S2-state thus induced by preflashes was identical with the modified S2-state that could be induced in dark-low pH-treated Photosystem II by excitation at 0°C after neutralization to pH 6.5. It was inferred that in low pH-treatment, modified S2-state can be formed from both S2- and S3-states, but its yield from the latter is much higher than from the former, consistent with the early results by Boussac et al. obtained for NaCl-EGTA-light or NaCl-citrate-light treatment.

Original languageEnglish
Pages (from-to)71-78
Number of pages8
JournalPhotosynthesis research
Issue number1
Publication statusPublished - Apr 1992
Externally publishedYes


  • Ca
  • Photosystem II
  • S-state
  • low pH-treatment
  • manganese
  • oxygen evolution

ASJC Scopus subject areas

  • Biochemistry
  • Plant Science
  • Cell Biology


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