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1Author    E. De Frenne, J. Eberspächer, F. Lingens, W. SchäferRequires cookie*
 Title    Bacterial Hydroxylation of Pyrazon Compounds  
 Abstract    In cell suspensions of bacteria grown with 5-amino-4-chloro-2-phenyl-3 (2H)-pyridazinone (pyra­ zon) as sole source of carbon o-methyl-pvrazon and /n-methyl-pyrazon were converted to the cor­ responding hydroxymethyl compounds. p-Methyl-pyrazon was not metabolized. 
  Reference    (Z. Naturforsch. 29c, 283 [1974]; eingegangen am 14. Dezember 1973) 
  Published    1974 
  Keywords    Bacterial Degradation, Bacterial Hydroxylation, Herbicides 
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 TEI-XML for    default:Reihe_C/29/ZNC-1974-29c-0283.pdf 
 Identifier    ZNC-1974-29c-0283 
 Volume    29 
2Author    A. Trebst, H. WietoskaRequires cookie*
 Title    Hemmung des photosynthetischen Elektronentransports von Chloroplasten durch Metribuzin * Mode of Action and Structure-Acitivity-Relationships of the Aminotriazinone Herbicide Metribuzin Inhibition of Photosynthetic Electron Transport in 'Chloroplasts by M etribuzin  
 Abstract    The influence of the aminotriazinone herbicide Metribuzin on photosynthetic reactions of iso­ lated chloroplasts is investigated. Metribuzin inhibits all Hill-reactions when water is the electron donor, but not photoreductions by photosystem I at the expense of an artificial electron donor. The PIso-value is 6.7. Cyclic photophosphorylation is not affected by Metribuzin. Measurements of the prompt and delayed fluorescence of the photosynthetically active chlorophyll support the notion, that Metribuzin inhibits photosynthetic electron flow between the primary and secondary electron acceptor of photosystem II (Q and plastoquinone). The relationship of inhibitory potency to chemical structure is investigated by comparing a number of related aminotriazinones. The effect of various substituents is discussed. E in le itu n g 
  Reference    (Z. Naturforsch. 30c, 499 [1975]; eingegangen am 7. April 1975) 
  Published    1975 
  Keywords    Photosynthesis, Chloroplasts, Herbicide, Metribuzin, Aminotriazinone 
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 TEI-XML for    default:Reihe_C/30/ZNC-1975-30c-0499.pdf 
 Identifier    ZNC-1975-30c-0499 
 Volume    30 
3Author    J.J S Van Rensen, D. Wong, GovindjeeRequires 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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 TEI-XML for    default:Reihe_C/33/ZNC-1978-33c-0413.pdf 
 Identifier    ZNC-1978-33c-0413 
 Volume    33 
4Author    H. K. KleudgenRequires 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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 TEI-XML for    default:Reihe_C/34/ZNC-1979-34c-0110.pdf 
 Identifier    ZNC-1979-34c-0110 
 Volume    34 
5Author    PeterM. Fredericks, LindsayA. SummersRequires cookie*
 Title    Synthesis and Biological Activity of Aminomethylphosphonic Acids Related to the Herbicide Glyphosate  
 Abstract    Several aminomethylphosphonic acids related to the herbicide glyphosate have been syn­ thesised and their post-emergent herbicidal properties studied. 
  Reference    Z. Naturforsch. 36c, 242 (1981); received September 301980 
  Published    1981 
  Keywords    Aminomethylphosphonic Acids, Herbicides, Glyphosate Analogues 
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 TEI-XML for    default:Reihe_C/36/ZNC-1981-36c-0242.pdf 
 Identifier    ZNC-1981-36c-0242 
 Volume    36 
6Author    K. K. Arl-Josef, UnertRequires 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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 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-0476.pdf 
 Identifier    ZNC-1984-39c-0476 
 Volume    39 
7Author    A. Trebst, B. D. Epka, S. M. Ridley, A. F. HawkinsRequires 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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 TEI-XML for    default:Reihe_C/40/ZNC-1985-40c-0391.pdf 
 Identifier    ZNC-1985-40c-0391 
 Volume    40 
8Author    A. Trebst, E. HarthRequires 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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 TEI-XML for    default:Reihe_C/29/ZNC-1974-29c-0232.pdf 
 Identifier    ZNC-1974-29c-0232 
 Volume    29 
9Author    D. Urbach, M. Suchanka, W. UrbachRequires 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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 TEI-XML for    default:Reihe_C/31/ZNC-1976-31c-0652.pdf 
 Identifier    ZNC-1976-31c-0652 
 Volume    31 
10Author    H. K. Lichtenthaler, H. K. KleudgenRequires 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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 TEI-XML for    default:Reihe_C/32/ZNC-1977-32c-0236.pdf 
 Identifier    ZNC-1977-32c-0236 
 Volume    32 
11Author    S. Reimer, K. Link, A. TrebstRequires 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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 TEI-XML for    default:Reihe_C/34/ZNC-1979-34c-0419.pdf 
 Identifier    ZNC-1979-34c-0419 
 Volume    34 
12Author    A. Trebst, S. R. Eim Er, W. Draber, H. J. KnopsRequires 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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 TEI-XML for    default:Reihe_C/34/ZNC-1979-34c-0831.pdf 
 Identifier    ZNC-1979-34c-0831 
 Volume    34 
13Author    KennethW. Right, J. R. CorbettRequires cookie*
 Title    Biochemistry of Herbicides Affecting Photosynthesis  
 Abstract    This paper reviews the inhibitory effects of herbicides at three locations within photosynthetic electron transport, on photophosphorylation, and on pigm ent synthesis. 
  Reference    Z. Naturforsch. 34c, 966 (1979); received May 24 1979 
  Published    1979 
  Keywords    Herbicides, Photosynthesis, Pigm ent Synthesis, Inhibition 
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 TEI-XML for    default:Reihe_C/34/ZNC-1979-34c-0966.pdf 
 Identifier    ZNC-1979-34c-0966 
 Volume    34 
14Author    Klaus Pfister, CharlesJ. ArntzenRequires 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 
15Author    ErichF. Elstner, W. OsswaldRequires 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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 TEI-XML for    default:Reihe_C/35/ZNC-1980-35c-0129.pdf 
 Identifier    ZNC-1980-35c-0129 
 Volume    35 
16Author    Magdolna Droppa, Sándor Dem, G. Ábor, H. OrváthRequires cookie*
 Title    Two Sites of Inhibition of the Photosynthetic Electron Transport Chain by the Herbicide Trifluralin  
 Abstract    The effect o f trifluralin on the photosynthetic electron transport has been investigated by oxygen evolution and thermoluminescence m easurem ents. The results confirm the earlier observations that trifluralin at low concentrations blocks electron transport between the two photosystems probably at the same site as DBMIB does. A t higher concentrations however, trifluralin inhibits the reaction from H aO -*■ /?BQ also and affects the thermoluminescence of chloroplasts in a manner sim ilar to DCM U. These results suggest that trifluralin has a second inhibitory site therefore the use o f trifluralin as a specific inhibitor o f electron transport has to be questioned. 
  Reference    Z. Naturforsch. 36c, 853—855 (1981); received June 25 1981 
  Published    1981 
  Keywords    Herbicide, Inhibition, Photosynthetic Electron Transport, Trifluralin, Thermoluminescence 
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 TEI-XML for    default:Reihe_C/36/ZNC-1981-36c-0853.pdf 
 Identifier    ZNC-1981-36c-0853 
 Volume    36 
17Author    Henrik Laasch, Klaus Pfister, Wolfgang UrbachRequires 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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 TEI-XML for    default:Reihe_C/36/ZNC-1981-36c-1041.pdf 
 Identifier    ZNC-1981-36c-1041 
 Volume    36 
18Author    Bernhard HuchzermeyerRequires cookie*
 Title    Energy Transfer Inhibition Induced by Nitrofen  
 Abstract    The herbicide nitrofen was shown to act as an energy transfer inhibitor. The results proved nitrofen to act by inhibiting nucleotide exchange on the chloroplast coupling factor. A strong correlation was found between the inhibition o f phosphorylation, ATPase activity, and nucleotide exchange. These results are discussed in terms of a regulatory effect o f tightly bound A D P on the enzymatic activity o f the chloroplast coupling factor. 
  Reference    Z. Naturforsch. 37c, 787—792 (1982); received April 30/June 8 1982 
  Published    1982 
  Keywords    Herbicides, Nitrofen, Energy Transfer Inhibition, Photophosphorylation, N ucleotide Exchange 
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 TEI-XML for    default:Reihe_C/37/ZNC-1982-37c-0787.pdf 
 Identifier    ZNC-1982-37c-0787 
 Volume    37 
19Author    W. Im, F. J. Vermaas, G. Ern O, R. Enger, J. A. Arles, RntzenRequires 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 
20Author    Klaus Pfister, U. Lrich, S. ChreiberRequires cookie*
 Title    Comparison of Diuron-and Phenol-Type Inhibitors: Additional Inhibitory Action at the Photosystem II Donor Site  
 Abstract    Inhibitors o f photosystem II reactions from the "diuron-type" and "phenol-type" have been compared regarding their m echanism o f action. "Diuron-" as well as "phenol-type" inhibitors act at the acceptor site o f photosystem II by displacing the secondary acceptor quinone Q B from its binding site. "Phenol-type" inhibitors additionally interfere with the donor site, which is demonstrated in studies o f chlorophyll fluorescence and lum inescence. This m echanism o f action is shown to be similar but not identical to that reported for hydroxylam ine. 
  Reference    Z. Naturforsch. 39c, 389 (1984); received D ecem ber 1 1983 
  Published    1984 
  Keywords    Herbicides, Photosynthesis, Fluorescence, Lum inescence, Inhibitors 
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 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-0389.pdf 
 Identifier    ZNC-1984-39c-0389 
 Volume    39