| | 1 | Author
| G. Á Bor Horváth, M. Agdolna, D. Roppa, Ágnes Puská | Requires cookie* | | | Title
| Fluorescence Induction Characteristics of Wild-Type and Herbicide-Resistant Strain of the Photosynthetic Bacterium Rhodobacter capsulatus  | | | | Abstract
| Fluorescence induction characteristics have been studied in wild-type and atrazine-resistant mutant o f Rhodobacter capsulatus. Fluorescence induction was found to be a useful technique to monitor the altered electron transfer in the atrazine-resistant mutants as well as in the differ ent membrane fractions o f wild-type R. capsulatus. In both cases, the proportion o f the fast rise o f variable fluorescence was increased indicating the enhancement o f QA. In the mutant strain, the / 50 value o f triazine herbicide terbutryn was increased by 1 0 0 -fold whereas the natu ral resistance o f R . capsulatus against diuron was abolished by the mutation. | | | |
Reference
| Z. Naturforsch. 45c, 452 (1990); received N ovem ber 9 1989 | | | |
Published
| 1990 | | | |
Keywords
| Fluorescence Induction, Electron Transport, Herbicide, Purple Bacteria, Photosynthesis | | | |
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| default:Reihe_C/45/ZNC-1990-45c-0452.pdf | | | | Identifier
| ZNC-1990-45c-0452 | | | | Volume
| 45 | |
| 2 | Author
| JeffA. Nemson, Anastasios Melis | Requires cookie* | | | Title
| Light-Induced Oxidation-Reduction Reactions of Photosystem II in Dichlorophenyl-dimethyl Urea (DCM U) Inhibited Thylakoids | | | | Abstract
| Illumination o f thylakoid membranes in the presence o f 3-(3',4'-dichlorophenyl)-1,1-di-methyl urea (D C M U) causes the reduction o f the primary quinone acceptor QA o f photosys tem II (PS II) and the storage o f a positive charge on the donor side o f the photochem ical reac tion center. These oxidation-reduction reactions are accompanied by characteristic changes o f absorbance in the ultra-violet region o f the spectrum. The PS II-related absorbance difference spectra (2 5 0 -3 5 0 nm) were compared in control and hydroxylamine-treated thylakoid mem branes, and in thylakoids suspended in the presence o f carbonyl cyanide-/7-(trifluoromethoxy)-phenylhydrazone (FCCP). The light minus dark difference spectra were dominated by the QA minus QA difference spectrum. Qualitatively, the three spectra were identical in the 3 0 0 -3 5 0 nm region, however, they showed distinct differences in the 2 5 0 -3 0 0 nm region. The latter arose because o f different contributions from the donor side o f PS II in the thylakoid membrane o f the three samples. The result suggested that FCCP acts as the ultimate electron donor in D C M U -poisoned chloroplasts. Therefore, the absorbance difference spectrum in the presence o f FCCP reflected a contribution from the QA minus QA com ponent only. D econvolu tion o f the absorbance difference spectra o f control and hydroxylamine-treated thylakoids yielded difference spectra attributed to the oxidation o f a com ponent on the donor side o f PS II. This com ponent did not conform with the known M n(III) — ■ > M n(IV) transition. R ath er, it indicated the oxidation o f a modified form o f Mn in the presence o f D C M U , probably a Mn(II) —> M n(III) transition. The results are discussed in terms o f the use o f D C M U -poisoned thylakoid membranes in the quantitation o f the primary quinone acceptor Q A by spectro-photom etric approaches. | | | |
Reference
| Z. Naturforsch. 45c, 258 (1990); received July 25/August 21. 1989 | | | |
Published
| 1990 | | | |
Keywords
| Absorbance Difference Spectra, Photosystem II, Electron Transport, Primary Quinone Acceptor, Electron D onor Tyrosine | | | |
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| default:Reihe_C/45/ZNC-1990-45c-0258.pdf | | | | Identifier
| ZNC-1990-45c-0258 | | | | Volume
| 45 | |
| 3 | Author
| Jack Dekker, RonaldG. Burmester | Requires cookie* | | | Title
| Differential Pleiotropy in a psbA Gene Mutant of Brassica napus Implies Altered Temporal Photosynthesis and Thermal Tolerance | | | | Abstract
| Studies were conducted to test the hypothesis that the mutation to the psbA. plastid gene that confers s-triazine resistance (R) also results in an altered diurnal pattern o f photosynthetic car bon reduction (CER) relative to that o f the susceptible (S) wild-type. In all experiments CER approximated the increasing and decreasing light levels during the diurnal. S C ER exceeded that o f R during the midday period, but R CER was greater early and late in the diurnal at 25 °C. R CER exceeded that o f S for most o f the diurnal at 35 °C and in older, crowded, nitrogen-starved plants. These studies support the stated hypothesis and indicate a more complex model o f photosynthetic productivity than previously observed. An assessment o f the photosynthetic competence o f either biotype may be a function o f the time o f day or the environmental condi tions the plants are exposed to, especially temperature. | | | |
Reference
| Z. Naturforsch. 45c, 474 (1990); received October 18 1989 | | | |
Published
| 1990 | | | |
Keywords
| Photosystem II, D -l Protein, Electron Transport, C hronobiology, Diurnal Rhythms | | | |
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| default:Reihe_C/45/ZNC-1990-45c-0474.pdf | | | | Identifier
| ZNC-1990-45c-0474 | | | | Volume
| 45 | |
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