Estimation of the steady-state cyclic electron flux around PSI in spinach leaf discs in white light, CO2-enriched air and other varied conditions

Jiancun Kou, Shunichi Takahashi, Riichi Oguchi, Da Yong Fan, Murray R. Badger, Wah Soon Chow

Research output: Contribution to journalArticlepeer-review

30 Citations (Scopus)


Cyclic electron flux (CEF) around PSI is essential for efficient photosynthesis and aids photoprotection, especially in stressful conditions, but the difficulty in quantifying CEF is non-trivial. The total electron flux through PSI (ETR1) and the linear electron flux (LEFO2) through both photosystems in spinach leaf discs were estimated from the photochemical yield of PSI and the gross oxygen evolution rate, respectively, in CO2-enriched air. ΔFlux = ETR1 - LEFO2 is an upper estimate of CEF. Infiltration of leaf discs with 150 μM antimycin A did not affect LEFO2, but decreased ΔFlux 10-fold. ΔFlux was practically negligible below 350 μolphotonsm -2s-1, but increased linearly above it. The following results were obtained at 980 μolphotonsm-2s-1. ΔFlux increased 3-fold as the temperature increased from 5°C to 40°C. It did not decline at high temperature, even when LEFO 2 decreased. ΔFlux increased by 80% as the relative water content of leaf discs decreased from 100 to 40%, when LEFO 2 decreased 2-fold. The method of using ΔFlux as a non-intrusive upper estimate of steady-state CEF in leaf tissue appears reasonable when photorespiration is suppressed. Journal compilation

Original languageEnglish
Pages (from-to)1018-1028
Number of pages11
JournalFunctional Plant Biology
Issue number10
Publication statusPublished - 2013
Externally publishedYes


  • Antimycin A
  • Cyclic electron flow
  • Linear electron flow
  • P700
  • Photosystem I

ASJC Scopus subject areas

  • Agronomy and Crop Science
  • Plant Science


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