title: Singlet oxygen production in herbicide-treated photosystem II.
abstract: Photo-generated reactive oxygen species in herbicide-treated photosystem II were investigated by spin-trapping. While the production of .OH and O2-* was herbicide-independent, 1O2 with a phenolic was twice that with a urea herbicide. This correlates with the reported influence of these herbicides on the redox properties of the semiquinone QA-* and fits with the hypothesis that 1O2 is produced by charge recombination reactions that are stimulated by herbicide binding and modulated by the nature of the herbicide. When phenolic herbicides are bound, charge recombination at the level of P+*Pheo-* is thermodynamically favoured forming a chlorophyll triplet and hence 1O2. With urea herbicides this pathway is less favourable.
authors.affiliation: Institut für Biologie II, Biochemie der Pflanzen, Universität Freiburg, Schänzlestr. 1, 79104, Freiburg, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Fufezan
authors.forename: A William
authors.initials: AW
authors.lastname: Rutherford
authors.forename: Anja
authors.initials: A
authors.lastname: Krieger-Liszkay
mesh_terms: D001665:Binding Sites; D002462:Cell Membrane / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D004237:Diuron / Q000494:pharmacology; D004578:Electron Spin Resonance Spectroscopy; D006540:Herbicides / Q000494:pharmacology*; D008027:Light; D045342:Light-Harvesting Protein Complexes; D009570:Nitriles / Q000494:pharmacology; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000187:drug effects*; D045332:Photosystem II Protein Complex; D017382:Reactive Oxygen Species; D018724:Spinacia oleracea; D014508:Urea / Q000494:pharmacology
chemical_list: D006540:Herbicides; D045342:Light-Harvesting Protein Complexes; D009570:Nitriles; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D017382:Reactive Oxygen Species; D002734:Chlorophyll; D014508:Urea; D004237:Diuron; C006826:bromoxynil; D010100:Oxygen