Performance of active Photosystem II centers in photoinhibited pea leaves

Gert Schansker, Jack J.S. Van Rensen

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Abstract

Effects of photoinhibition on photosynthesis in pea (Pisum sativum L.) leaves were investigated by studying the relationship between the severity of a photoinhibitory treatment (measured as F(v)/F(m)) and several photoacoustic and chlorophyll a fluorescence parameters. Because of the observed linear relationship between the decline of F(v)/F(m) and the potential oxygen evolution rate determined by the photoacoustic method, the parameter F(v)/F(m) was used as an indicator for the severity of photoinhibition. Our analysis revealed that part of the Photosystem II (PS II) reaction centers is inactive in oxygen evolution and is also less sensitive to photoinhibition. Correcting the parameter q(p) (fraction of open PS II reaction centers) for inactive PS II centers unveiled a strong increase of q(p) in severely inhibited pea leaves, indicating that the inactivated active centers do no longer contribute to q(p) and that photoinhibition has an all or none effect on PS II centers. Analysis of q(E) (energy quenching) demonstrated its initial increase possibly associated with dephosphorylation of LHC II. Analysis of q(I) (photoinhibition dependent quenching) showed that the half-time of recovery of q(I) increases steeply below an F(v)/F(m) of 0.65. This increase of the relaxation half-time corresponds with a decrease of the electron transport rate J and tentatively indicates that the supply of ATP, needed for the recovery, starts to decrease. The data indicate the necessity of correcting for inactive centers in order to make valuable conclusions about effects of photoinhibition on photosynthetic parameters.

Original languageEnglish
Pages (from-to)175-184
Number of pages10
JournalPhotosynthesis research
Volume62
Issue number2
Publication statusPublished - Jan 1 1999

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Keywords

  • Chlorophyll fluorescence quenching
  • F(v)/F(m)
  • LHC II phosphorylation
  • Photoacoustic spectroscopy
  • Photoinhibition
  • Pisum

ASJC Scopus subject areas

  • Biochemistry
  • Plant Science
  • Cell Biology

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