| | 3 | Author
| J.J S Van Rensen, D. Wong, Govindjee | Requires cookie* | | | Title
| Characterization of the Inhibition of Photosynthetic Electron Transport in Pea Chloroplasts by the Herbicide 4,6-Dinitro- o-cresol by Comparative Studies with 3-(3,4-Dichlorophenyl)-l,l- dimethylurea  | | | | Abstract
| An attempt to characterize the mechanism of inhibition of photosynthetic electron transport in isolated pea chloroplasts by the herbicide 4,6-dinitro-o-cresol (DNOC) by a comparison with the effects of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) revealed the following: | | | |
Reference
| Z. Naturforsch. 33c, 413 (1978); received April 12 1978 | | | |
Published
| 1978 | | | |
Keywords
| Photosynthesis, Electron Transport, Fluorescence, Herbicides | | | |
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| default:Reihe_C/33/ZNC-1978-33c-0413.pdf | | | | Identifier
| ZNC-1978-33c-0413 | | | | Volume
| 33 | |
| 4 | Author
| H. K. Kleudgen | Requires cookie* | | | Title
| Die Wirkung von Simazin auf die Bildung der plastidären Prenyllipide in Keimlingen von Hordeum vulgare L. Effect of Simazine on Formation of Chloroplasts Prenyllipids in Seedlings of H ordeum vulgare L | | | | Abstract
| Barley seedlings were grown for 7, 10 or 13 days under continuous white light (Fluora lamps) on a nutrient solution containing simazine (2-chloro-4,6-bis-(ethylamino)-s-triazine, 10, 100 j u m) . Accumulation of chlorophylls and in part of carotenoids was increasingly enhanced depending on age and concentrations applied. The ratio chlorophyll a/b decreased on this line in 10 and 13 day old plants, the ratio xanthophylls//?-carotene and the ratio chlorophyll a/prenylquinones (plasto-quinone-90x. + red. , a-tocopherol, a-tocoquinone) increased. The way how these prenyllipid ratios are changed in 10 and 13 day old plants is characteristic of a shade type adaptation, as it was shown earlier for other herbicides inhibiting photosystem II. In 7 day old plants the ratio chlorophyll a/prenylquinones decreased. Photosynthetic activity (Hill-reaction) was enhanced in the simazine plants. The ratio chlorophyll a/b was higher, the ratio xanthophylls//?-carotene was lower than in the older seedlings. Similar changes of prenyllipid ratios like in 7 day seedlings and a higher Hill activity were also found in plants grown under blue light (sun type adaptation) as compared to red light (shade type adaptation). This points to similar metabolic changes in the chloroplasts which could be related to a common site of regulation, perhaps the endogenuous cytokinins. The Hill activity, increasing with age in the 10 and 13 day plants, indicates that the mode of action of simazine may be a multiple process resulting to a parallel formation of shade type and sun type characteristics. | | | |
Reference
| Z. Naturforsch. 34c, 110 (1979); eingegangen am 13. November 1978 | | | |
Published
| 1979 | | | |
Keywords
| Herbicide, Simazine, Prenyllipids, Chloroplasts, Regulation | | | |
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| default:Reihe_C/34/ZNC-1979-34c-0110.pdf | | | | Identifier
| ZNC-1979-34c-0110 | | | | Volume
| 34 | |
| 6 | 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 | |
| 7 | Author
| A. Trebst, B. D. Epka, S. M. Ridley, A. F. Hawkins | Requires cookie* | | | Title
| Inhibition of Photosynthetic Electron Transport by Halogenated 4-Hydroxy-pyridines | | | | Abstract
| Herbicidal halogen substituted 4-hydroxypyridines are inhibitors of photosynthetic electron flow in isolated thylakoid membranes by interfering with the acceptor side of photosystem II. Tetrabromo-4-hydroxypyridine, the most active compound found, has a pl50-value of 7.6 in the inhibition of oxygen evolution in both the reduction of an acceptor of photosystem I and an acceptor of photosystem II. The new inhibitors displace both metribuzin and ioxynil from the membrane. The 4-hydroxypyridines, like ioxynil, have unimpaired inhibitor potency in Tris-treated chloroplasts, whereas the DCMU-type family of herbicides does not. It is suggested that 4-hydroxypyridines are complementary to phenol-type inhibitors, and a common essential element is proposed. The 4-hydroxypyridines do not inhibit photosystem I or non-cyclic electron flow through the cytochrome b/f complex. But they do have a second inhibition site in photosynthetic electron transport since they inhibit ferredoxin-catalyzed cyclic electron flow, indicating an antimycin-like property. A comparison of the in vitro potency of the compounds with the in vivo potency shows no correlation. A major herbicidal mode of action of the group is related to the inhibition of carotenoid synthesis, and access to the chloroplast lamellae in vivo for inhibition of electron transport may be restricted. | | | |
Reference
| Z. Naturforsch. 40c, 391—399 (1985); received February 28 1985 | | | |
Published
| 1985 | | | |
Keywords
| Herbicides, Hydroxypyridines, Inhibitors, Photosynthesis | | | |
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| default:Reihe_C/40/ZNC-1985-40c-0391.pdf | | | | Identifier
| ZNC-1985-40c-0391 | | | | Volume
| 40 | |
| 8 | Author
| A. Trebst, E. Harth | Requires cookie* | | | Title
| Herbicidal N-Alkylated-Ureas and Ringclosed N-Acylamides as Inhibitors of Photosystem II | | | | Abstract
| The inhibitory action of some herbicides on photosynthetic electron flow at photosystem I I in isolated chloroplasts was investigated. Emphasis in the study is on compounds, whose chemical structure seemed to be in disaccordance with the basic structural element, proposed to be required for a photosystem II inhibitor. The effective inhibition of photosynthetic oxygen evolution by N-alkylated urea-, pyrrolidone-and by substituted pyridazine-derivatives without a free NH-group is reported. A revised basic chemical structural element responsible for inhibition is deduced in order to include lactames (ringclosed N-acylamides) with and without hetero atoms. From this new groups of potential inhibitors, like triazolone-, thiadiazolone-and oxadiazolone-derivatives may be conceived. | | | |
Reference
| (Z. Naturforsch. 29c, 232 [1974]; received February 4 1974) | | | |
Published
| 1974 | | | |
Keywords
| Inhibitor, Herbicides, Photosynthesis, Photosystem II, Chloroplasts | | | |
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| default:Reihe_C/29/ZNC-1974-29c-0232.pdf | | | | Identifier
| ZNC-1974-29c-0232 | | | | Volume
| 29 | |
| 9 | Author
| D. Urbach, M. Suchanka, W. Urbach | Requires cookie* | | | Title
| Effect of Substituted Pyridazinone Herbicides and of Difunone (EMD-IT 5914) on Carotenoid Biosynthesis in Green Algae | | | | Abstract
| The carotenoid biosynthesis of the green alga A n kistrodesm u s braunii is blocked if these cells are cultured in presence of sublethal doses of pyridazinone herbicides (San 9789, San 6706, BASF 44521) or of the herbicide difunone (EMD-IT 5914). The amount of colored carotenoids normally found in these algae is reduced drastically and the precursors phytoene and phytofluene are ac cumulated. Furthermore a decrease in the chlorophyll level occurs in the treated cells, but there is a stronger loss of chlorophyll a, resulting in a lowering of the chlorophyll a/b ratio with time. Concerning the activity of substituted pyridazinones leading to inhibition of carotenoid biosynthesis this effect can be related to the chemical structure of these compounds: a trifluoromethyl substitu tion of the phenyl ring an d a mono-or dimethyl substitution of the amine (San 9789, San 6706) or a methoxy group instead of the substituted amine (BASF 44521) are required both for this effect. Other pyridazinone derivatives with eith er a trifluoromethyl substitution of the phenyl ring (San 9774) or a dimethyl substitution of the amine (San 9785) or a methoxy group (BASF 13761) are without any effect on the pigment pattern of these algae. | | | |
Reference
| (Z. Naturforsch. 31c, 652 [1976]; received July 28 1976) | | | |
Published
| 1976 | | | |
Keywords
| Herbicides, Pyridazinone, Difunone, Carotenoid Biosynthesis, Green Algae | | | |
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| default:Reihe_C/31/ZNC-1976-31c-0652.pdf | | | | Identifier
| ZNC-1976-31c-0652 | | | | Volume
| 31 | |
| 10 | Author
| H. K. Lichtenthaler, H. K. Kleudgen | Requires cookie* | | | Title
| Effect of the Herbicide San 6706 on Biosynthesis of Photosynthetic Pigments and Prenylquinones in Raphanus and in Hordeum Seedlings | | | | Abstract
| The pyridazinone herbicide San 6706 blocks chlorophyll and carotenoid formation simultaneously in a correlated way in both Raphanus and Hordeum seedlings. With decreasing carotenoid content the carotenoid precursor phytoene appears in San 6706-treated plants. The accumulation of the chloroplast prenylquinones (plastoquinone-9, a-tocopherol, <x-toco-quinone and vitamin Kj) is much less affected. This indicates that the biosynthesis of C20-and C45-prenyl chains (geranyl-geraniol, phytol and solanesol) which are incorporated in prenylquinones is not blocked by San 6706. It is assumed that the block of chlorophyll and carotenoid formation is due to one basic inhibi tion mechanism. The possibility that San 6706 may interfere with chloroplast ribosome formation, is discussed. | | | |
Reference
| (Z. Naturforsch. 32c, 236 [1977]; received December 13 1976) | | | |
Published
| 1977 | | | |
Keywords
| Herbicide, Pyridazinone, Prenyl Biosynthesis, Carotenoids, Prenylquinones | | | |
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| default:Reihe_C/32/ZNC-1977-32c-0236.pdf | | | | Identifier
| ZNC-1977-32c-0236 | | | | Volume
| 32 | |
| 11 | Author
| S. Reimer, K. Link, A. Trebst | Requires cookie* | | | Title
| Comparison of the Inhibition of Photosynthetic Reactions in Chloroplasts by Dibromothymoquinone, Bromonitrothymol and Ioxynil | | | | Abstract
| The inhibition of photosynthetic electron flow in broken chloroplasts by dibromothymoquinone and dibromothymohydroquinone (DBMIBH2) is reversed by dithiothreitol (DTT) as well as by serum albumin. The reversal of DBMIBH2 inhibition by DTT shows a time lag, that of DBMIB only, when chloroplasts and DBMIB had been preilluminated. This is to show that chloroplasts reduce DBMIB and that probably DBMIBH2 is the actual inhibitor species. Bromonitrothymol, ioxynil and related inhibitory phenolic compounds have a different relation ship of inhibitory potency to chemical structure than DCMU and the analogous triazinone herbicide metribuzin but nevertheless inhibit photosynthetic electron flow at the same functional site. This is supported by the finding that labelled metribuzin is displaced from the thylakoid membrane by bromonitrothymol and ioxynil indicating identical binding sites. On the other hand inhibition by the phenolic inhibitors bromonitrothymol and ioxynil but not that of DCMU and metribuzin has a time lag of about 4 min. | | | |
Reference
| Z. Naturforsch. 34c, 419 (1979); received October 31 1978 | | | |
Published
| 1979 | | | |
Keywords
| Photosynthesis, Inhibition, Herbicides, Dibromo-thymoquinone, Bromonitrothymol, Ioxynil | | | |
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| default:Reihe_C/34/ZNC-1979-34c-0419.pdf | | | | Identifier
| ZNC-1979-34c-0419 | | | | Volume
| 34 | |
| 12 | Author
| A. Trebst, S. R. Eim Er, W. Draber, H. J. Knops | Requires cookie* | | | Title
| The Effect of Analogues of Dibromothymoquinone and of Bromonitrothymol on Photosynthetic Electron Flow | | | | Abstract
| Alkyl substituted derivatives of halogenated p-benzoquinones, of halogenated /7-nitrophenols, and of 2,4-dinitrophenols were tested in the inhibition of photosynthetic electron flow in chloro plasts. The effect of the compounds on photoreductions by photosystem I or II, on a TMPD bypass in NADPH formation and the reversibility of the inhibition by dithiothreitol is used to distin guish between an inhibition site before or after plastoquinone function, i. e. between a DBMIB versus a DCMU inhibition pattern. It is shown, that different isopropyl and /-butyl substituted halogenated p-benzoquinones are as effective and specific as DBMIB in the inhibition of plastoquinone function. Alkyl substituted /^-nitrophenols, with an additional halogen-or nitro-group at C-2, are shown to be effective electron flow inhibitors. The new potent nitrophenol derivatives inhibit at the site of DCMU action, nevertheless they do not contain the basic chemical element essential for inhibi tion common to DCMU and its many herbicidal analogues. Small changes in the ring-substitution can alter the inhibition pattern from a DCMU typ to a DBMIB typ inhibition. | | | |
Reference
| Z. Naturforsch. 34c, 831 (1979); received June 1 1979 | | | |
Published
| 1979 | | | |
Keywords
| Photosynthesis, Inhibitors, Herbicides, Dibromothymoquinone, Nitrophenols, Chloroplast | | | |
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| default:Reihe_C/34/ZNC-1979-34c-0831.pdf | | | | Identifier
| ZNC-1979-34c-0831 | | | | Volume
| 34 | |
| 14 | Author
| Klaus Pfister, CharlesJ. Arntzen | Requires cookie* | | | Title
| The Mode of Action of Photosystem II-Specific Inhibitors in Herbicide-Resistant Weed Biotypes | | | | Abstract
| This report reviews studies which provide evidence defining the mode of action and site of action of photosystem II (PS II) herbicides; the involvement of the secondary electron carrier on the reducing side of PS II (called B) is indicated as the target site for these compounds. These studies of the action of PS II-inhibitors were perform ed in chloroplasts of various weed species in order to define the mechanism which is responsible for herbicide tolerance at the level of chloroplast mem branes in newly discovered triazine-resistant weed biotypes. M any species of triazine-resistant weed biotypes have been collected in N orth America and Europe. W here data is available, these plants have been found to share the following common fe atu res: a) they were discovered in areas where triazine herbicides had been used repeatedly, b) resistance to the triazines is extrem e; it is not due to a m inor shift in herbicidal response, c) no changes in herbicide uptake, translocation or metabolism — as compared to susceptible bio types — can be detected, d) resistance is selective for only certain classes of photosynthetic herbicides, and, e) chloroplasts isolated from triazine-resistant weeds display high preferential resistance to the triazines in assays of photosystem II partial reactions. To focus on the mechanism which regulates preferential herbicide activity, we have characterized susceptible and resistant chloroplasts in the presence and absence of herbicides. Properties of the PS II complex of chloroplasts from several different triazine-resistant weed biotypes share the fol lowing tr a its : a) the herbicide binding site (as measured by direct binding of radiolabeled herbicides or by in hibition experiments) is modified such that the affinity for triazines is dram atically reduced. b) alterations in response to many PS II-herbicides occur such th at the triazine-resistant chloro plasts are very strongly resistant to all sym m etrical triazines, strongly resistant to assymmetrical triazinones, partially resistant to pyridazones and uracils, only slightly resistant to ureas or amides, and increasingly susceptible to nitrophenols, phenols and the herbicide bentazon (all as compared to susceptible chloroplasts), c) there is a change in the reaction kinetics of the electron transport step between the prim ary and secondary electron acceptors (referred to as Q and B), and d) in two examples, specific small changes in a m em brane polypeptide can be detected in the resistant thylakoids. We suggest that certain amino acids or segments of the apoprotein of B (the bound quinone which acts as the secondary electron carrier) are modified or deleted in these chloroplasts. Such a polypeptide change could affect both the redox poising of the Q~/B reaction pair, and the specific binding of herbicides. | | | |
Reference
| Z. Naturforsch. 34c, 996—1009 (1979); received June 29 1979 | | | |
Published
| 1979 | | | |
Keywords
| Herbicide, Resistance, Photosynthesis, Electron Transport, Inhibitors | | | |
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| | | | | TEI-XML for
| default:Reihe_C/34/ZNC-1979-34c-0996.pdf | | | | Identifier
| ZNC-1979-34c-0996 | | | | Volume
| 34 | |
| 15 | 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 | |
| 17 | Author
| Henrik Laasch, Klaus Pfister, Wolfgang Urbach | Requires cookie* | | | Title
| Comparative Binding of Photosystem II — Herbicides to Isolated Thylakoid Membranes and Intact Green Algae | | | | Abstract
| The binding of the photosystem II herbicides diuron (DCM U), atrazine (s-triazine), ioxynil and dinoseb (substituted phenols) to isolated spinach thylakoids was saturated in less than 2 min in the dark. In intact cells of the green alga Ankistrodesmus b. it took 10 to 20 min to reach the binding equilibrium. Binding affinity of diuron, atrazine, dinoseb, measured as equilibrium binding constants, was found to be comparable in isolated thylakoids and intact algal cells. For ioxynil, reduced binding affinity was observed in algae. The concentration of binding sites in thylakoids and intact cells was determined to be 300-500 chl/inhibitor binding site, suggesting a 1:1 stoichiometry between bound herbicide and electron transport chains. In intact cells only the phenol herbicides ioxynil and dinoseb showed increased concentrations of binding sites. Strong correlation of herbicide binding and inhibition o f electron transport was found for diuron in isolated thylakoids and intact cells. In thylakoids this is valid also for atrazine and dinoseb. For ioxynil a difference between the amount of binding and inhibition was found. This correlation o f herbicide binding and inhibition proves that binding specifically occurs at the inhibition site at photosystem H. In addition to the specific binding, for all four herbicides studied, (except for ioxynil in thylakoids) unspecific binding was observed in thylakoids as well as in algae, which was not related to inhibition. | | | |
Reference
| Z. Naturforsch. 36c, 1041—1049 (1981); received July 13 1981 | | | |
Published
| 1981 | | | |
Keywords
| Herbicides, Herbicide Binding, Photosynthesis, Thylakoids, Algae | | | |
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| default:Reihe_C/36/ZNC-1981-36c-1041.pdf | | | | Identifier
| ZNC-1981-36c-1041 | | | | Volume
| 36 | |
| 19 | 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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| | | | | TEI-XML for
| default:Reihe_C/39/ZNC-1984-39c-0368.pdf | | | | Identifier
| ZNC-1984-39c-0368 | | | | Volume
| 39 | |
|
