| | 1 | Author
| N. Orbert, G. Rotjohann, David Messdaghi, Wolfgang Kowallik | Requires 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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| default:Reihe_C/54/ZNC-1999-54c-0209.pdf | | | | Identifier
| ZNC-1999-54c-0209 | | | | Volume
| 54 | |
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