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'Photosystem II Herbicides' in keywords Facet   Publication Year 1982  [X]
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1982[X]
1Author    K. H. GrumbachRequires cookie*
 Title    Herbicides which Inhibit Electron Transport or Produce Chlorosis and Their Effect on Chloroplast Development in Radish Seedlings I. Chlorophyll a Fluorescence Transients and Photosystem II Activity  
 Abstract    Diuron and bentazon are very strong inhibitors o f the photosynthetic electron transport in isolated radish chloroplasts. The chlorosis producing herbicide SAN 6706 also inhibited the photosystem II dependent oxygen evolution. Aminotriazole had no effect. The inhibitor concentration for 50% inhibition o f photosystem II activity was 10-7 m for diuron and 10-4 m for bentazon and SAN 6706 respectively. Diuron and bentazon quenched the chlorophyll a fluorescence transients in isolated radish chloroplasts drastically, while aminotriazole was not effective. It was o f particular interest that the bleaching herbicide SAN 6706 inhibited photosystem II dependent oxygen evolution in a similar concentration as bentazon but had no effect on the chlorophyll a-fluorescence transients suggesting that SAN 6706 is not binding to the same site o f the electron transport chain as diuron and bentazon. Apart from their direct influence on electron transport in isolated photosynthetically active chloroplasts the photosystem II and bleaching herbicides assayed also strongly affected photosynthesis in radish seedlings that were grown in the presence o f the herbicides for a long time. As already obtained using isolated chloroplasts, photosystem II dependent oxygen evolution like the chlorophyll a fluorescence transients were strongly inhibited by the photosystem II herbicides diuron and bentazon. A reduction but no inhibition o f photosystem II activity was observed in plants that were grown in the presence o f aminotriazole. The pyridazinone SAN 6706 was behaving contradictory. In partly green plants photosystem II activity was still maintained and even higher than in untreated plants while in albinistic plants no photosynthetic activity was detected. 
  Reference    Z. Naturforsch. 37c, 268—275 (1982); received December 3 1981 
  Published    1982 
  Keywords    Bleaching Herbicides, Photosynthesis, Photosystem II Herbicides, Photosystem II Activity, Chlorophyll Fluorescence 
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 TEI-XML for    default:Reihe_C/37/ZNC-1982-37c-0268.pdf 
 Identifier    ZNC-1982-37c-0268 
 Volume    37 
2Author    C. Buschm, K.H G RuRequires cookie*
 Title    Herbicides which Inhibit Electron Transport or Produce Chlorosis and Their Effect on Chloroplast Development in Radish Seedlings II. Pigment Excitation, Chlorophyll Fluorescence and Pigment-Protein Complexes  
 Abstract    DCM U, bentazon, amitrole and SA N 6706 affected the form ation o f the pigm ent-protein com ­ plexes and caused drastic alterations in the absorption o f light and in the transfer o f the absorbed energy in the antennae systems. Bentazon and D C M U , photosystem II inhibitors, did not change the pigment absorption and fluorescence excitation spectra. After application o f both herbicides the long wavelength fluorescence em ission band at 740 nm was reduced sim ilar as in young d e ­ veloping leaves. Although D C M U and bentazon inhibit the photosynthetic electron transport at the same site, bentazon mainly suppressed the form ation o f the photosystem I com plexes C P Ia and CPI while DC M U mainly reduced the photosystem II com plex CPa. Bentazon specifically en­ hanced the formation o f LHCP3. This may be im portant for the increased grana stacking in plas-tids from bentazon treated plants. The bleaching herbicides amitrole and SA N 6706 inhibited the form ation o f carotenoids lead ­ ing to an accumulation o f lycopene, phytofluene and phytoene, w hile the accum ulation o f chloro­ phylls was suppressed. This bleaching effect was m ost pronounced during growth under higher intensities o f light. In weak light (100 lux) am itrole reduced the long wavelength fluorescence maximum but the fluorescence excitation was not affected. W ith am itrole at 2000 lux and SAN 6706 at 100 lux the long wavelength em ission band was further decreased and the fluores­ cence excitation spectra point to a less efficient energy transfer to chlorophyll a. The fluorescence spectra changed due to herbicide treatment resem bled those o f not yet fully developed leaves. In contrast to the photosystem II herbicides the bleaching herbicides am itrole and SA N 6706 had a similar effect on the formation o f pigm ent-protein com plexes. After growth at 2000 lux both herbicides suppressed the formation o f the photosystem I com plex C P Ia and the photosystem II complex CPa. At 100 lux only the formation o f C P Ia was affected. Except for D C M U all herbicides assayed primarily changed the form ation o f photosystem I. 
  Reference    Z. Naturforsch. 37c, 632 (1982); received April 2 1982 
  Published    1982 
  Keywords    Bleaching Herbicides, Carotenoids, Chlorophylls, C hlorophyll Fluorescence, Photosystem II Herbicides, Pigm ent-Protein-Complexes 
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 TEI-XML for    default:Reihe_C/37/ZNC-1982-37c-0632.pdf 
 Identifier    ZNC-1982-37c-0632 
 Volume    37