Photosynthetic electron transport activity in heat-treated barley leaves: The role of internal alternative electron donors to photosystem II

Szilvia Z. Tóth, Gert Schansker, Gyozo Garab, Reto J. Strasser

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107 Citations (Scopus)

Abstract

Electron transport processes were investigated in barley leaves in which the oxygen-evolution was fully inhibited by a heat pulse (48 °C, 40 s). Under these circumstances, the K peak (∼ F400 μs) appears in the chl a fluorescence (OJIP) transient reflecting partial QA reduction, which is due to a stable charge separation resulting from the donation of one electron by tyrozine Z. Following the K peak additional fluorescence increase (indicating QA- accumulation) occurs in the 0.2-2 s time range. Using simultaneous chl a fluorescence and 820 nm transmission measurements it is demonstrated that this QA- accumulation is due to naturally occurring alternative electron sources that donate electrons to the donor side of photosystem II. Chl a fluorescence data obtained with 5-ms light pulses (double flashes spaced 2.3-500 ms apart, and trains of several hundred flashes spaced by 100 or 200 ms) show that the electron donation occurs from a large pool with t1/2 ∼ 30 ms. This alternative electron donor is most probably ascorbate.

Original languageEnglish
Pages (from-to)295-305
Number of pages11
JournalBiochimica et Biophysica Acta - Bioenergetics
Volume1767
Issue number4
DOIs
Publication statusPublished - Apr 1 2007

Keywords

  • 820 nm transmission
  • Alternative electron donor
  • Chlorophyll a fluorescence
  • Heat pulse
  • OJIP-transient
  • Photosystem II

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology

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