| | 1 | Author
| ErichF. Elstner, W. Osswald | Requires cookie* | | | Title
| Chlorophyll Photobleaching and Ethane Production in Dichlorophenyldimethylurea-(DCMU) or Paraquat-Treated Euglena gracilis Cells  | | | | Abstract
| Light dependent (35 Klux) chlorophyll bleaching in autotrophically grown Euglena gracilis cells at slightly acidic pH (6.5 —5.4) is stimulated by the photosystem II blockers DCMU and DBMIB (both 10~5 m) as well as by the autooxidizable photosystem I electron acceptor, paraquat (1 0 -3 m). Chlorophyll photobleaching is accompanied by the formation o f thiobarbituric acid — sensitive material ("malondialdehyde") and ethane. Both chlorophyll photobleaching and light dependent ethane formation are partially prevented by higher concentrations (10~* m) o f the autooxidizable photosystem II electron acceptor DBMIB or by sodium bicarbonate (25 m M). In vitro studies with cell free extracts (homogenates) from E. gracilis suggest that a-linolenic acid oxidation by excited (reaction center II) chlorophyll represents the driving force for both ethane formation and chlorophyll bleaching. Ethane formation thus appears to be a sensitive and non-destructive "in vivo'' marker for both restricted energy dissipation in photosystem II and, conditions yielding reactive oxygen species at the reducing side o f photosystem I. | | | |
Reference
| Z. Naturforsch. 35c, 129—135 (1980); received August 20/September 28 1979 | | | |
Published
| 1980 | | | |
Keywords
| Chlorophyll Bleaching, Herbicides, Euglena gracilis, Ethane, Fat Oxidation | | | |
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| default:Reihe_C/35/ZNC-1980-35c-0129.pdf | | | | Identifier
| ZNC-1980-35c-0129 | | | | Volume
| 35 | |
| 2 | Author
| E. F. Elstner, H. P. Fischer, W. Osswald, G. Kwiatkowski | Requires cookie* | | | Title
| Superoxide-and Ethane-Formation in Subchloroplast Particles: Catalysis by Pyridinium Derivatives | | | | Abstract
| Oxygen reduction by chloroplast lamellae is catalyzed by low potential redox dyes with E'0 values between -0 .3 8 V and -0 .6 V. Compounds o f E'0 values o f -0 .6 7 V and lower are inactive. In subchloroplast particles with an active photosystem I but devoid of photosynthetic electron transport between the two photosystems, the active redox compounds enhance chlorophyll bleaching, superoxide formation and ethane production independent on exogenous substrates or electron donors. The activities o f these compounds decrease with decreasing redox potential, with one exception: 1-methyl-4,4'-bipyridini urn bromide with an E'0 value o f lower -1 V (and thus no electron acceptor o f photosystem I in chloroplast lamellae with intact electron transport) stimulates light dependent superoxide formation and unsaturated fatty acid peroxidation in sub chloroplast particles, maximal rates appearing after almost complete chlorophyll bleaching. Since this activity is not visible with compounds with redox potentials below -0 .6 V lacking the nitrogen atom at the 1-position o f the pyridinium substituent, we assume that 1 -methyl-4,4'-bi-pyridinium bromide is "activated" by a yet unknown light reaction. | | | |
Reference
| Z. Naturforsch. 35c, 770—775 (1980); received May 23/June 6 1980 | | | |
Published
| 1980 | | | |
Keywords
| Superoxide, Lipid Peroxidation, Ethane, Chloroplasts, Pyridinium Salts | | | |
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| default:Reihe_C/35/ZNC-1980-35c-0770.pdf | | | | Identifier
| ZNC-1980-35c-0770 | | | | Volume
| 35 | |
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