Imaging of NPQ and ROS formation in tobacco leaves: Heat inactivation of the water-water cycle prevents down-regulation of PSII

Éva Hideg, Péter B. Kós, Ulrich Schreiber

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Non-photochemical chlorophyll fluorescence quenching (NPQ) plays a major role in the protection of the photosynthetic apparatus against damage by excess light, which is closely linked to the production of reactive oxygen species (ROS). The effect of a short heat treatment on NPQ and ROS production was studied with detached tobacco leaves by fluorescence imaging of chlorophyll and of the ROS sensor dye HO-1889NH. NPQ was stimulated >3-fold by 3 min pre-treatment at 44°C, in parallel with suppression of CO2 uptake, while no ROS formation could be detected. In contrast, after 3 min pre-treatment at 46°C, NPQ was suppressed and ROS formation was indicated by quenching of HO-1889NH fluorescence. After 3 min pre-treatment at 46°C and above, partial inactivation of ascorbate peroxidase and light-driven accumulation of H2O2 was also observed. These data are discussed as evidence for a decisive role of the Mehler ascorbate peroxidase or water-water cycle in the formation of the NPQ that reflects down-regulation of PSII.

Original languageEnglish
Pages (from-to)1879-1886
Number of pages8
JournalPlant and Cell Physiology
Issue number12
Publication statusPublished - Dec 1 2008



  • Fluorescence imaging
  • Heat stress-reactive oxygen species (ROS)
  • Mehler ascorbate peroxidase (MAP) cycle
  • PAM fluorometry
  • Photosynthetic electron transport

ASJC Scopus subject areas

  • Physiology
  • Plant Science
  • Cell Biology

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