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1999 (1)
1Author    N. Orbert, G. Rotjohann, David Messdaghi, Wolfgang KowallikRequires cookie*
 Title    Oxygen Uptake during Photosynthesis of Isolated Pea Chloroplasts  
 Abstract    Mass spectrometric analysis of the gas exchange of illuminated leaflets of 10-14 d old pea seedlings revealed not only 160 2-liberation from photosynthetic H2160-splitting, but also uptake of ls0 2, applied to the gas phase of the reaction vessel. Isolated intact chloroplasts of such leaflets suspended in a medium containing N aH C 03 and glycerate 3-phosphate, on irradiation with blue (A. 448 nm) or red (X 679 nm) light also produced 160 2 from water oxidation and consumed 180 2 from the gas phase. The two reactions were saturated at the same quantum fluence rates. Uptake of 18oxygen was not affected by inhibitors of mito­ chondrial respiration (alternative pathway included), such as rotenone (5 x l0 -5 m), antimycin A (5 x l0 ~6 m), KCN (10-3 m), SHAM (10-3 m), or propylgallate (10-3 m). It was, however, absent, when photosynthetic 16oxygen evolution was completely inhibited by DCMU (10-? m). DBMIB (10~5 m), assumed to prevent electron flow from plastoquinone pool to the cyto­ chrome ö6//-complex, suppressed photosynthetic oxygen evolution, but did not impair uptake of 180 2. A similar result was obtained at application of 4 x l0 _e; m antimycin A. The data are interpreted to show a drain off to molecular oxygen of light-excited electrons from the photosynthetic electron transport chain at the site of plastoquinone pool during photosynthesis. This corresponds to chlororespiration, originally described for Chlamydomo-nas in darkness by Bennoun (1982). It is discussed, whether 0 2-uptake during photosynthesis is an additional means for providing ATP for photosynthetic C 0 2-reduction by increasing the proton gradient across the thylakoid membrane. 
  Reference    Z. Naturforsch. 54c, 209—219 (1999); received October 5/November 13 1998 
  Published    1999 
  Keywords    Pisum sativum, Chlororespiration, 18Oxygen Consumption, Photophosphorylation, Intact Isolated Chloroplasts 
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 TEI-XML for    default:Reihe_C/54/ZNC-1999-54c-0209.pdf 
 Identifier    ZNC-1999-54c-0209 
 Volume    54