| | 1 | Author
| K. K. Arl-Josef, Unert | Requires cookie* | | | Title
| The Diphenyl-Ether Herbicide Oxyfluorfen: A Potent Inducer of Lipid Peroxidation in Higher Plants  | | | | Abstract
| Measurements o f ethane and ethylene as indices o f in vivo lipid peroxidation and o f chemically-induced stress, respectively, were done on mustard seedlings (Sinapis alba), treated with oxy-fluorfen[2-chloro-l-(3-ethoxy-4-nitrophenoxy)-4-(trifluorom ethyl)benzene]. W hen seedlings were exposed to low light intensity o f 14 W /m 2, only stress-ethylene production but not per oxidative ethane evolution was significantly higher over 1 0 days in herbicide-treated seedlings than in the untreated control. Exposure to high light intensity o f 390 W /m 2 did not increase stress-ethylene production in oxyfluorfen-treated plants after 24 h. Lipid peroxidation, however, measured as ethane evolution, was substantially higher after 24 h in herbicide-treated plants, exposed to high light intensity, than in the control, and peroxidation was directly related to strong oxidation o f antioxidants and to severe membrane dam age. | | | |
Reference
| Z. Naturforsch. 39c, 476—481 (1984); received September 15 1983 | | | |
Published
| 1984 | | | |
Keywords
| Herbicide, Diphenyl Ether, Peroxidation, Antioxidants | | | |
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| default:Reihe_C/39/ZNC-1984-39c-0476.pdf | | | | Identifier
| ZNC-1984-39c-0476 | | | | Volume
| 39 | |
| 2 | Author
| W. Im, F. J. Vermaas, G. Ern O, R. Enger, J. A. Arles, Rntzen | Requires cookie* | | | Title
| Herbicide/Quinone Binding Interactions in Photosystem II | | | | Abstract
| Many inhibitors prevent the oxidation o f the primary electron-accepting quinone (Q A) by the secondary quinone (Q B) in photosystem II by displacem ent o f Q B from its binding site. On the other hand, plastoquinone-1 and 6-azido-5-decyl-2,3-dim ethoxy-/?-benzoquinone displace herbicides. Binding studies show the herbicide/quinone interaction to be (apparently) competitive. The herbicide binding is influenced differentially by various treatments. In this paper it is shown that the affinity of, for example, brom oxynil is decreased by thylakoid unstacking or by light-or reductant-induced reduction o f certain thylakoid com ponents, whereas atrazine affinity remains unchanged. Furthermore, absence o f H C O j in the presence o f form ate leads to an affinity decrease o f bromoxynil and atrazine, but to an increase in i-dinoseb affinity. Other differential photosystem II herbicide effects are known from the literature. Since different and unrelated groups o f Q A oxidation inhibitors have been found, and because o f the above-mentioned dissim ilarities in binding characteristics for different inhibitor groups, the hypothesis o f non-identical, but "overlapping" binding sites for different herbicide groups and the native quinone must be more extensively defined. In this m anuscript we evaluate both the competitive herbicide/quinone binding m odel, and a m odel in which binding o f one ligand alters the protein conformation resulting in a dram atic decrease in the binding affinity o f ligands from other chemical groups; in this model ligands from the sam e or related chem ical groups bind competitively. Thus, the latter model proposes that only one herbicide or quinone m olecule can be bound with high affinity to the herbicide/quinone binding environm ent, but it depends on the chemical structure o f the ligands whether the binding interaction betw een two ligands is truly competitive or more indirect (allosteric), m ediated through the protein conform ation. | | | |
Reference
| Z. Naturforsch. 39c, 368 (1984); received D ecem ber 1 1983 | | | |
Published
| 1984 | | | |
Keywords
| Herbicide, Photosystem II, Plastoquinone, Photosynthesis, A llosteric interaction | | | |
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| default:Reihe_C/39/ZNC-1984-39c-0368.pdf | | | | Identifier
| ZNC-1984-39c-0368 | | | | Volume
| 39 | |
| 4 | Author
| A. Trebst, W. D. Onner, W. D. Raber | Requires cookie* | | | Title
| Structure Activity Correlation of Herbicides Affecting Plastoquinone Reduction by Photosystem II: Electron Density Distribution in Inhibitors and Plastoquinone Species | | | | Abstract
| Molecular orbital calculations o f the net charge and the n charge distribution in several inhibitors and herbicides o f the functionally related group o f the diuron and dinoseb type are reported. They confirm the m odel that urea, am inotriazinone and triazine herbicides all have in common a positive ^-charge at a particular atom considered to be essential for binding. Phenol type inhibitors have different charge distribution and a m odel for their essential features is presented. The calculations support the finding that two different subunits with different binding characteristics are involved in inhibitor and plastoquinone function on the acceptor side o f photosystem II. Force-field model building and MO calculations o f the charge distribution o f a plastoquinone analogue with a butenyl side chain, o f two o f its sem iquinone forms and o f the hydroquinone, are reported, as well as their conform ation with the lowest energy content and their likely anionic forms. | | | |
Reference
| Z. Naturforsch. 39c, 405—411 (1984); received D ecem ber 23 1983 | | | |
Published
| 1984 | | | |
Keywords
| Herbicides, Plastoquinone, MO Calculation, Photosystem II | | | |
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| default:Reihe_C/39/ZNC-1984-39c-0405.pdf | | | | Identifier
| ZNC-1984-39c-0405 | | | | Volume
| 39 | |
| 5 | Author
| K. N. Singh, J. Prakash, A. K. Agarwal, G. S. Singhal | Requires cookie* | | | Title
| Interaction of Herbicides with Pea Chloroplasts | | | | Abstract
| We have studied the effect o f three herbicides viz., triazole, pyrazon and m etribuzin on total chlorophyll, carotenoids and cell protein in leaves, and PS II and PS I activity in the chloroplasts isolated from control and herbicide treated pea plants. Pyrazon and m etribuzin at 10 (iM concen tration affect these parameters resulting in the chlorosis o f the leaves. | | | |
Reference
| Z. Naturforsch. 39c, 464—467 (1984); received January 20 1984 | | | |
Published
| 1984 | | | |
Keywords
| Pea, Chloroplast, Herbicides, M etribuzin, Pyrazon, Triazole | | | |
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| default:Reihe_C/39/ZNC-1984-39c-0464.pdf | | | | Identifier
| ZNC-1984-39c-0464 | | | | Volume
| 39 | |
| 6 | Author
| M. D. Arie-Jose, Elrieu | Requires cookie* | | | Title
| The Effects of 3-(3,4-Dichlorophenyl)-l,l-dimethylurea on the Photosynthetic Oxygen Complex | | | | Abstract
| In the presence o f trypsin and ferricyanide as external electron acceptor, lettuce chloroplasts are resistant to DCM U, showing that the inhibitory site o f D C M U is only situated on the accep tor side o f photosystem II. However, kinetic properties o f the oxygen evolving com plex are m od i fied at non-saturating concentrations o f D C M U . These changes are interpreted in terms o f a model with two distinct charges separation systems on the sam e center: the auxiliary donor-acceptor system D Q L implicated in the transitions S| -» • S 2 and S2 -*■ S 3 would be m uch less affected by DCM U than the main donor-acceptor system Y Q H after the first flash. | | | |
Reference
| Z. Naturforsch. 39c, 347—350 (1984); received N ovem ber 28 1983 | | | |
Published
| 1984 | | | |
Keywords
| Herbicides, Oxygen Evolution, Photosystem II, Electron Acceptors, Electron D onors | | | |
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| default:Reihe_C/39/ZNC-1984-39c-0347.pdf | | | | Identifier
| ZNC-1984-39c-0347 | | | | Volume
| 39 | |
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