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The Effect of pH on the Nonphotochemical Quenching of Chlorophyll Fluorescence of Thylakoid Membranes

  • Young-Jae Eu
  • Sujata R. Mishra
  • Ismayil S. Zulfugarov
  • Chin Bum Lee
  • Choon-Hwan Lee

Abstract

Nonphotochemical quenching (NPQ) is important means in plants to dissipate excess light energy. To determine whether the pH of the stromal part of thylakoid membrane affects the development of NPQ, the chlorophyll fluorescence induction curves of thylakoid samples at various pHs were examined with imaging system. The maximum fluorescence(Fm) showed a bell-shaped curve with peak from pH 7 to 8. The minimum fluorescence (Fo) was not affected by low pH, but increased in high pH. The pH-dependency of photochemical efficiency was the inverse of that for Fo and changed little at low pH, but decreased at high pH. The effect of pH on electron transport activity from photosystem II to photosystem I was similar to that on Fm. Fm did not recover after turning off actinic light at pH lower than 6.5, resulting in negative qE. The variation of qE at various pHs of thylakoid suspension medium showed a bell-shaped curve with pH maximum at 7.5. These results suggest that the sensor of thylakoid membranes detects the relative proton gradient between lumen and stroma of thylakoids, but not the absolute value of pH of the lumen.

Keywords

Nonphotochemical quenching chlorophyll fluorescence pH thylakoid imaging 

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Copyright information

© Springer Science + Business Media, B.V. 2008

Authors and Affiliations

  • Young-Jae Eu
    • 1
  • Sujata R. Mishra
    • 1
  • Ismayil S. Zulfugarov
    • 1
  • Chin Bum Lee
    • 2
  • Choon-Hwan Lee
    • 1
  1. 1.Department of Molecular BiologyPusan National UniversityPusanKorea
  2. 2.Department of Molecular BiologyDong-eui UniversityPusanKorea

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