NPQ activation reduces chlorophyll triplet state formation in the moss Physcomitrella patens

Donatella Carbonera, Caterina Gerotto, Bianca Posocco, Giorgio Mario Giacometti, Tomas Morosinotto

Research output: Contribution to journalArticlepeer-review


Plants live in variable environments in which light intensity can rapidly change, from limiting to excess conditions. Non-photochemical quenching (NPQ) is a regulatory mechanism which protects plants from oxidative stress by dissipating excess Chl singlet excitation. In this work, the physiological role of NPQ was assessed by monitoring its influence on the population of the direct source of light excess damage, i.e., Chl triplets (3Chl*). 3Chl* formation was evaluated in vivo, with the moss Physcomitrella patens, by exploiting the high sensitivity of fluorescence-detected magnetic resonance (FDMR). A dark adapted sample was compared with a pre-illuminated sample in which NPQ was activated, the latter showing a strong reduction in 3Chl* yield. In line with this result, mutants unable to activate NPQ showed only a minor effect in 3Chl* yield upon pre-illumination.The decrease in 3Chl* yield is equally experienced by all the Chl pools associated with PSII, suggesting that NPQ is effective in protecting both the core and the peripheral antenna complexes. Moreover, the FDMR results show that the structural reorganization in the photosynthetic apparatus, required by NPQ, does not lead to the formation of new 3Chl* traps in the LHCs. This work demonstrates that NPQ activation leads to effective photoprotection, promoting a photosystem II state characterized by a reduced probability of 3Chl* formation, due to a decreased singlet excited state population, while maintaining an efficient quenching of the 3Chl* eventually formed by carotenoids.

Original languageEnglish
Pages (from-to)1608-1615
Number of pages8
JournalBiochimica et Biophysica Acta - Bioenergetics
Issue number9
Publication statusPublished - Sep 2012


  • Carotenoid
  • FDMR
  • LHC
  • NPQ
  • Physcomitrella patens
  • Triplets

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Cell Biology


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