Characterization of the alterations of the chlorophyll a fluorescence induction curve after addition of Photosystem II inhibiting herbicides

M. Hiraki, J.J.S. van Rensen, W.J. Vredenberg, K. Wakabayashi

Research output: Contribution to journalArticleAcademicpeer-review

31 Citations (Scopus)

Abstract

The effects of Photosystem II inhibiting herbicides, 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron), atrazine and two novel 2-benzylamino-1,3,5-triazine compounds, on photosynthetic oxygen evolution and chlorophyll a fluorescence induction were measured in thylakoids isolated from Chenopodium album (wild type and atrazine-resistant plants) and cyanobacterial intact cells. The resistant plants have a mutation of serine for glycine at position 264 of the D1 protein. Diuron and two members of a novel class of 2-benzylamino-1,3,5-triazine compounds were almost as active in wild-type as in atrazine-resistant thylakoids, indicating that the benzylamino substitution in the novel triazines may be important for the lack of resistance in these atrazine-resistant plants. The inhibition by the herbicides of oxygen evolution in the cyanobacteria was somewhat lower than in the thylakoids of Chenopodium album wild type, probably caused by a slower uptake in the intact cells. The so-called OJIP fluorescence induction curve was measured during a one second light pulse in the absence and in the presence of high concentrations of the four herbicides. In the presence of a herbicide we observed an increase of the initial fluorescence at the origin (Fo'), a higher J level, and a decreased steady state at its P level (Fp). The increase to Fo' and the decreased leveling Fp are discussed. After dark adaptation about 25% of the reaction centers are in the S-0 state of the oxygen evolving complex with an electron on the secondary electron accepting quinone, Q(B). The addition of a herbicide causes a transfer of the electron on Q(B) to the primary quinone acceptor, Q(A), and displacement of Q(B) by the herbicide; the reduced Q(A) leads to a higher Fo'. The decrease of Fp in the presence of the herbicides is suggested to be caused by inhibition of the photo-electrochemical stimulation of the fluorescence yield.
Original languageEnglish
Pages (from-to)35-46
JournalPhotosynthesis Research
Volume78
DOIs
Publication statusPublished - 2003

Keywords

  • photosynthetic electron-transport
  • triazine-resistant
  • chenopodium-album
  • reducing side
  • chloroplasts
  • cyanobacteria
  • derivatives
  • evolution
  • kinetics
  • plants

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