| | 2 | Author
| SeymourSteven Brody | Requires cookie* | | | Title
| Flash Photolysis of Liposomes Containing Chlorophyll and Zeaxanthin, as a Function of Temperature (2 °—34 °C)  | | | | Abstract
| The transfer o f triplet excitation from chlorophyll to zeaxanthin in lip osom es is a function o f temperature and pigment concentration. At 525 nm both chlorophyll and zeaxanthin triplet states are observed. The result is a biphasic increase in absorption. The rise time o f absorption by the chlorophyll triplet is much faster, than by the zeaxanthin triplet. With increasing temperature the contribution o f absorption by zea xanthin (relative to that o f chlorophyll) at 525 nm increases, and its rise tim e gets faster. At high ratios o f zeaxanthin to chlorophyll, temperature has less effect on both the rise tim e and absorption by the zeaxanthin triplet state. The chlorophyll triplet is measured at 780 nm. It decays faster with increasing temperature and or increasing ratio o f zeaxanthin to chlorophyll. The results are interpreted in terms of: increasing fluidity o f the lipid lip osom e with tem per ature, formation o f zeaxanthin-chlorophyll com plexes at high ratios o f zeaxanthin and chloro phyll, presence o f different lipid phases in the lip osom e bilayer. | | | |
Reference
| Z. Naturforsch. 39c, 1108—1111 (1984); received June 15 1984 | | | |
Published
| 1984 | | | |
Keywords
| Chlorophyll, Carotenoid, Liposomes, Triplet States, Excitation Energy Transfer | | | |
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| | | | | TEI-XML for
| default:Reihe_C/39/ZNC-1984-39c-1108.pdf | | | | Identifier
| ZNC-1984-39c-1108 | | | | Volume
| 39 | |
| 3 | Author
| Jürgen Feierabend | Requires cookie* | | | Title
| Comparison of the Action of Bleaching Herbicides | | | | Abstract
| Among chlorosis-inducing herbicides that interfere with carotenoid synthesis two groups o f different potency can be discriminated (group 1; aminotriazole amd haloxidine; group 2 with more extensive photodestructions: pyridazinone herbicides and difunon). After application o f herbicides o f group 2 colored carotenoids were com pletely absent and preexisting chlorophyll was degraded by photochem ical reactions requiring high light intensity and 0 2, that occurred also at 0 °C . In treatments with group 1 herbicides direct photodegradation o f chlorophyll was not sufficient to generate the chlorosis. Light-induced interference with constituents o f the chloroplast protein synthesis apparatus being more sensitive to ph otooxidative dam age than chlorophyll, appeared to indirectly m ediate the chlorosis. In the absence o f chloroplast protein synthesis further chlorophyll accum ulation is prevented. Photodegradation o f chlorophyll in the presence o f group 2 herbicides involved the participation o f 0 2~ radicals and was accom panied by lipid peroxidation. In all herbicide treatments the catalase activity o f the leaves was very low. Only in the presence o f group 2 herbicides chloroplast enzym es o f cytoplasm ic origin (e.g. NADP-glyceraldehyde-3-phosphate dehydrogenase) were also inactivated. Rapid inactivation o f catalase as well as o f N A D P-glyceraldehyde-3-phosphate dehydrogenase was induced by exposure o f dim-light-grown herbicide-treated leaves to bright light, also at 0 ° C . In treatments with herbicides o f group 2 also other peroxisom al enzymes (e.g. glycolate oxidate, hydroxy-pyruvate reductase) were affected. The elim ination o f these peroxisom al enzym es also appeared to depend on photooxidative processes o f the chloroplast. | | | |
Reference
| Z. Naturforsch. 39c, 450 (1984); received N ovem ber 4 1983 | | | |
Published
| 1984 | | | |
Keywords
| Bleaching Herbicides, Carotenoids, Catalase, Chlorosis, Leaf Peroxisom es, Photooxidation | | | |
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| default:Reihe_C/39/ZNC-1984-39c-0450.pdf | | | | Identifier
| ZNC-1984-39c-0450 | | | | Volume
| 39 | |
| 4 | Author
| K. H. Grumbach | Requires cookie* | | | Title
| Herbicides which Interfere with the Biosynthesis of Carotenoids and Their Effect on Pigment Excitation, Chlorophyll Fluorescence and Pigment Composition of the Thylakoid Membrane | | | | Abstract
| Plants grown in the presence o f the herbicides assayed synthesized chlorophylls during growth at low fluence rates. Subsequent irradiation with higher fluence rates o f red light induced a strong chlorosis with SAN 6706 being a much stronger herbicide than J 852 or am ino-triazole. All herbicides assayed also changed the content and com position o f chlorophylls, carotenoids and pigment-protein-complexes o f the thylakoid m em brane and therefore the pigm ent excitation and chlorophyll fluorescence em ission spectra o f the plastid. W ith increasing herbicide toxicity the main characteristic em ission bands at 690 and 730 nm disappeared and new em ission bands at 715 (J 852) and 700 nm (SA N 6706) appeared. Such "artificial" m em branes with a changed pigment composition were very susceptible to light. Presented data m ay be taken as evidence, that the lack o f photoprotective cyclic carotenoids caused by the specific action o f a bleaching herbicide is the primary event that m ay lead to a disturbed form ation o f the thylakoid membrane and its destruction by light and oxygen. | | | |
Reference
| Z. Naturforsch. 39c, 455—458 (1984); received N ovem ber 29 1983 | | | |
Published
| 1984 | | | |
Keywords
| Bleaching Herbicides, Carotenoids, Chlorophylls, F luorescence, Pigm ent Excitation | | | |
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| default:Reihe_C/39/ZNC-1984-39c-0455.pdf | | | | Identifier
| ZNC-1984-39c-0455 | | | | Volume
| 39 | |
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