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21Author    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 
22Author    A. Trebst, W. D. Onner, W. D. RaberRequires 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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 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-0405.pdf 
 Identifier    ZNC-1984-39c-0405 
 Volume    39 
23Author    K. N. Singh, J. Prakash, A. K. Agarwal, G. S. SinghalRequires 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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 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-0464.pdf 
 Identifier    ZNC-1984-39c-0464 
 Volume    39 
24Author    Angela Weber, Elke Fischer, Helmut Schipp Von Branitz, Ulrich LüttgeRequires cookie*
 Title    The Effects of the Herbicide Sethoxydim on Transport Processes in Sensitive and Tolerant Grass Species I. Effects on the Electrical Membrane Potential and Alanine Uptake  
 Abstract    Sethoxydim is a postemergence herbicide used to control grass weeds. Application at concen-trations higher than 0.1 mM to leaf segments of the sensitive grass species Poa pratensis and Festuca ovina and the tolerant species Poa annua and Festuca rubra, caused a reduction of the electrical membrane potential (AE). The depolarization was reversible and depended linearly on the herbicide concentration. The passive diffusion component of AE was not affected by sethoxy-dim indicating that the herbicide did not change passive permeability characteristics of the plas-malemma. Consequently sethoxydim reduced the active component of AE that depended on primary active transport processes across the plasmalemma. Moreover, sethoxydim increased the reduction of AE of grass leaf cells that was associated with the onset of H + -amino acid cotrans-port. Simultaneously the uptake of alanine into leaf segments was reduced. From these results it had to be concluded that the plasmalemma-bound H + -ATPase was inhibited by sethoxydim in sensitive and tolerant grasses. In vitro ATP hydrolysis of plasmalemma vesicles isolated from grass leaves by polymer phase partitioning, however, was not inhibited by sethoxydim. Apparent-ly another primary active transport mechanism that may contribute to an electrochemical H + -gradient across the plasmalemma, i.e. a plasmalemma-bound redox system, should be the site of inhibition responsible for the membrane effects of sethoxydim observed in vivo. 
  Reference    Z. Naturforsch. 43c, 249—256 (1988); received December 23 1987 
  Published    1988 
  Keywords    Plasmalemma, Membrane ATPase, Herbicide, Sethoxydim, Amino Acid Uptake 
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 TEI-XML for    default:Reihe_C/43/ZNC-1988-43c-0249.pdf 
 Identifier    ZNC-1988-43c-0249 
 Volume    43 
25Author    Angela Weber, Ulrich LüttgeRequires cookie*
 Title    The Effects of the Herbicide Sethoxydim on Transport Processes in Sensitive and Tolerant Grass Species II. Effects on Membrane-Bound Redox Systems in Plant Cells  
 Abstract    Leaf slices of sethoxydim-sensitive (Poa pratensis, Festuca ovina) and tolerant (Poa annua, Festuca rubra) grass species were found to be able to reduce extracellular ferricyanide by electron transport across the plasmalemma. This reduction was inhibited by the herbicide sethoxydim, and the sensitive species were much more strongly affected than the tolerant ones. The inhibition was concentration dependent. Sethoxydim affected the electron transport in isolated Poo chloroplasts. Polarographic and photometric measurements of ferricyanide reduction suggested photosystem II to be the site of action. Inhibition occurred only in the sensitive species Poa pratensis and was linearly dependent on concentration. In isolated mitochondria from sensitive Zea mays coleop-tiles sethoxydim also acted as an inhibitor of electron transport. Only slight inhibition was meas-ured with mitochondria from tubers of tolerant potato (Solanum tuberosum). It is concluded that sethoxydim generally acts as inhibitor of membrane-bound redox systems. The specific inhibition of the plasmalemma-bound redox system of sethoxydim-sensitive plants could contribute to a selective action of the herbicide. 
  Reference    Z. Naturforsch. 43c, 257—263 (1988); received December 23 1987 
  Published    1988 
  Keywords    Sethoxydim, Herbicide, Redox Systems, Isolated Organelles, Plasmalemma 
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 TEI-XML for    default:Reihe_C/43/ZNC-1988-43c-0257.pdf 
 Identifier    ZNC-1988-43c-0257 
 Volume    43 
26Author    Walter Oettmeier, Klaus Masson, Andreas DonnerRequires cookie*
 Title    QSAR of Nitro-diphenylethers as Inhibitors of Cyclic Photophosphorylation  
 Abstract    A number of 25 nitro-diphenylethers have been synthesized and assayed for their inhibitory activity in N-methylphenazonium-methosulfate mediated cyclic photophosphorylation. Their p/50-values were in the range from 3.5 to 5.3. A QSAR-analysis revealed that the lipophilicity of the nitro-diphenylethers as expressed by Z:t played a major role. In addition, the Taft steric parameter £s in positions 6', 4' and 2' (in decreasing order) contributed to the inhibitory activity. For maximal biological activity, positions 4' and 6' should be left unsubstituted whereas a bulky substituent is required for position 2'. 
  Reference    Z. Naturforsch. 43c, 705—708 (1988); received May 31 1988 
  Published    1988 
  Keywords    Cyclic Photophosphorylation, Herbicides, Nitro-diphenylethers, Quantitative Structure-Activity Relationship 
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 TEI-XML for    default:Reihe_C/43/ZNC-1988-43c-0705.pdf 
 Identifier    ZNC-1988-43c-0705 
 Volume    43 
27Author    G. Á Bor Horváth, M. Agdolna, D. Roppa, Ágnes PuskáRequires cookie*
 Title    Fluorescence Induction Characteristics of Wild-Type and Herbicide-Resistant Strain of the Photosynthetic Bacterium Rhodobacter capsulatus  
 Abstract    Fluorescence induction characteristics have been studied in wild-type and atrazine-resistant mutant o f Rhodobacter capsulatus. Fluorescence induction was found to be a useful technique to monitor the altered electron transfer in the atrazine-resistant mutants as well as in the differ­ ent membrane fractions o f wild-type R. capsulatus. In both cases, the proportion o f the fast rise o f variable fluorescence was increased indicating the enhancement o f QA. In the mutant strain, the / 50 value o f triazine herbicide terbutryn was increased by 1 0 0 -fold whereas the natu­ ral resistance o f R . capsulatus against diuron was abolished by the mutation. 
  Reference    Z. Naturforsch. 45c, 452 (1990); received N ovem ber 9 1989 
  Published    1990 
  Keywords    Fluorescence Induction, Electron Transport, Herbicide, Purple Bacteria, Photosynthesis 
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 TEI-XML for    default:Reihe_C/45/ZNC-1990-45c-0452.pdf 
 Identifier    ZNC-1990-45c-0452 
 Volume    45 
28Author    Carl Fedtke, RobertH. Strang, Bayer Ag, Geschäftsbereich Pflanzenschutz, Biologische Anwendungstechnik, ForschungRequires cookie*
 Title    Synergistic Activity of the Herbicide Safener Dichlormid with Herbicides Affecting Photosynthesis  
 Abstract    Dichlormid, a safener for thiolcarbamate herbicides, was tank-mixed with several herbicidal inhibitors of photosystem II, or with the herbicide acifluorfen, and applied postemergence to Ipomoea hederacea plants. Dichlormid had no visible effects on the plants when applied alone, but interacted synergistically with the herbicides in the combination treatments. Dichlormid strongly decreased the ascorbic acid levels in the Ipom oea hederacea cotyledons. Ascorbate is known to protect plant tissue from photooxidative damage. The herbicides which interacted synergistically with dichlormid are believed to generate their phytotoxic action via the produc­ tion of excess singlet oxygen. It is suggested that the decreased ascorbate levels in the Ipomoea hederacea cotyledons after dichlormid treatment result in an impaired singlet oxygen scaveng­ ing system and consequently lead to increased plant damage in the presence of singlet oxygen generating herbicides. 
  Reference    Z. Naturforsch. 45c, 565—567 (1990); received October 13 1989 
  Published    1990 
  Keywords    Herbicide, Synergism, Safener, Oxygen Toxicity, Ascorbic Acid 
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 TEI-XML for    default:Reihe_C/45/ZNC-1990-45c-0565.pdf 
 Identifier    ZNC-1990-45c-0565 
 Volume    45 
29Author    Zsigmond Ekler, FerencD. UtkaRequires cookie*
 Title    Chemical Reactivity and Safener Activity of Acetal Compounds  
 Abstract    Although detailed examinations have been published on structure-activity relationships of herbicide safeners, only a few data are available on chemical reactivity-safener activity rela­ tionships. Chemical reactivity o f acetamide type compounds as well as their safener activity against thiocarbamate herbicides change with the number o f chlorine substituents in the order: non-chlorinated < monochloro < dichloro. Several compounds of another chemical group, acetals (e.g. MG-191, 2-dichloromethyl-2-methyl-l,3-dioxolane), are also effective safeners for thiocarbamate herbicides. According to our growth room studies, the safener activity o f ace­ tals also increases with increasing chlorine content up to two chlorine atoms on the same car­ bon. A number of differently chlorinated acetals have been synthesized and their acid-cata­ lyzed hydrolysis rate determined in order to establish a relationship between their bioactivity and chemical reactivity. The hydrolysis rate order of acetals containing no, one or two chlorine atoms: non-chlorinated > monochloro > dichloro, is just the opposite than what has been found for acetamides. Thus, safener activity of acetals increases with decreasing chemical reac­ tivity. The opposite reactivity order of acetamides and acetals can be explained by the different mechanisms of their hydrolysis. Dichloroacetals may not be effective safeners in their original structure. In plants, however, they can be biologically activated to active safeners by a trans­ formation other than hydrolysis. 
  Reference    Z. Naturforsch. 46c, 810—814 (1991); received March 26 1991 
  Published    1991 
  Keywords    Acetals, Hydrolysis, Herbicides, Herbicide Safeners, Zea mays (L) 
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 TEI-XML for    default:Reihe_C/46/ZNC-1991-46c-0810.pdf 
 Identifier    ZNC-1991-46c-0810 
 Volume    46 
30Author    Bernd Schneider, Manfred Stock, Gernot Schneider, HorstRobert Schütte, Klaus Schreiber, Angela Brauner, ErnstUlrich KaußmannRequires cookie*
 Title    Metabolism of Amitrole in Apple: I. Soluble Metabolites from Mature Fruits  
 Abstract    Mature fruits from apple trees contain residual amounts of radiolabel derived from soil-ap-plied [3,5-14C]amitrole. This report deals with characterization of the soluble part of this radio­ activity. By GC/MS of suitable derivatives 3-(l,2,4-triazol-l-yl)-2-aminopropionic acid was identi­ fied as a new metabolite of amitrole. Significant parts of radiolabel were incorporated into genuine plant products, indicating liberation of 14C 0 2 from the applied substance followed by reassimilation. Possible pathways of metabolism of amitrole within the system soil/apple tree are discussed. 
  Reference    Z. Naturforsch. 47c, 120—125 (1992); received June 18/October 24 1991 
  Published    1992 
  Keywords    Herbicide, Amitrole, Metabolism, Reassimilation, Structural Elucidation 
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 TEI-XML for    default:Reihe_C/47/ZNC-1992-47c-0120.pdf 
 Identifier    ZNC-1992-47c-0120 
 Volume    47 
31Author    A. Aiach, U. Bodner, U. JohanningmRequires cookie*
 Title    A Herbicide Resistant Euglena Mutant Carrying a Ser to Thr Substitution at Position 265 in the D 1 Protein of Photosystem II  
 Abstract    A herbicide resistant Euglena mutant (M SI) has been obtained by adapting wild type cells to increasing concentrations o f D C M U (3-(3',4'-dichlorophenyl)-l ,1-dimethylurea). Lower re­ sistance levels towards D C M U and metribuzin were observed in MSI when compared with Euglena or C hlam ydom onas mutants with Ser 264 to Ala substitutions. RNA-sequence analysis identified a Ser to Thr change at position 265 (equivalent to position 264 in other organisms), thus making it possible to compare the influence o f amino acids Ser, Ala and Thr at identical positions on the inhibitory effect o f structurally different herbicides in the same species. 
  Reference    Z. Naturforsch. 47c, 245 (1992); received October 31 1991 
  Published    1992 
  Keywords    Herbicides, D 1-Protein, Point M utation, Resistance, Euglena 
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 TEI-XML for    default:Reihe_C/47/ZNC-1992-47c-0245.pdf 
 Identifier    ZNC-1992-47c-0245 
 Volume    47 
32Author    R. Jockers, R. D. SchmidRequires cookie*
 Title    Synthesis of Long-Chain Triazine Aldehydes -Substrates of Bacterial Luciferase and Photosynthetic Inhibitors  
 Abstract    S-triazines are photosynthetic inhibitors. They have been substituted with co-aminoundeca-noic acid. The coupling products have been transformed into triazine aldehydes. These com ­ pounds displace radioactive terbutryn and have inhibitory effects on photosynthesis in plants and bacteria. Triazine aldehydes were shown to be effective substrates for bacterial luciferase. A competitive assay between photosystem-II-herbicides and aldehyde-labeled triazines is dis­ cussed. 
  Reference    Z. Naturforsch. 47c, 573—5 (1992); received April 7/June 15 1992 
  Published    1992 
  Keywords    Herbicides, Bacterial Luciferase, Triazines, Aldehyde, Photosystem II, Biosensor 
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 TEI-XML for    default:Reihe_C/47/ZNC-1992-47c-0573.pdf 
 Identifier    ZNC-1992-47c-0573 
 Volume    47 
33Author    H. Adar Kless3, Michal Oren-Shamirb, ItzhakO. Hadc, M. Arvin Edelm, Wim VermaasaRequires cookie*
 Title    Protein Modifications in the D 2 Protein of Photosystem II Affect Properties of the Q B/Herbicide-Binding Environment  
 Abstract    The D 2 protein contains an extended loop (the D-de loop) between helices D and de at the reducing side o f photosystem II (PS II). Characterization o f D 2 mutants o f the cyanobacte­ rium Synechocystis sp. PCC 6803 has indicated that the length and amino acid com position o f the D-de loop are not critical for basic PS II functions, although most o f the residues in that region are conserved phylogenetically. Here we show using herbicide binding and electron-flow inhibition measurements that drastic modifications in the D-de loop o f the D 2 protein modify the interaction o f some PS II-directed herbicides with their binding niche. The stability o f (semi-)reduced Q B in its binding pocket is altered in at least two o f the mutants, as indicated by a shifted peak temperature o f the thermoluminescence signal originating from charge recombi­ nation involving QB. These results suggest a close functional association between the D-de loop o f the D 2 protein and the Q B/herbicide-binding environment, which is viewed as being coordinated mostly by re­ sidues o f the D 1 protein. This represents one o f the first examples o f m odification o f the Q B/ herbicide-binding domain by mutations in the D 2 protein. 
  Reference    Z. Naturforsch. 48c, 185—190 (1993); received November 23 1992 
  Published    1993 
  Keywords    Herbicides, Plastoquinone, Photosystem II, Thermoluminescence, Cyanobacteria 
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 TEI-XML for    default:Reihe_C/48/ZNC-1993-48c-0185.pdf 
 Identifier    ZNC-1993-48c-0185 
 Volume    48 
34Author    HartmutB. Stegmann, Paul Schuler, Stefan Westphal, Edgar WagnerRequires cookie*
 Title    Oxidative Stress of Crops Monitored by EPR  
 Abstract    Treatm ent of leaves of spinach, corn, and peas with the herbicides paraquat, am itrole or acifluorfen leads to oxidative stress resulting in a light driven drastically increased production of ascorbic acid radical (monodehydroascorbic acid, M DAA) which could be dem onstrated by in vivo EPR analysis. A discrimination of the M D A A form ation between the action of elec­ tron uncouplers and catalase inhibitors can be achieved by observation of the radical rise ki­ netics. Significant M DAA signal intensities are detected in the darkness likewise. These signals are probably due to the action of ascorbic acid oxidase activated by membrane destruction. 
  Reference    Z. Naturforsch. 48c, 766—772 (1993); received M arch 3/July 1 1993 
  Published    1993 
  Keywords    Herbicides, Paraquat, Amitrole, Ascorbic Acid Radicals 
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 TEI-XML for    default:Reihe_C/48/ZNC-1993-48c-0766.pdf 
 Identifier    ZNC-1993-48c-0766 
 Volume    48 
35Author    Friedhelm Blobel, Jürgen Eberspächer, Siegfried Haug, Franz LingensRequires cookie*
 Title    eines M uconsäurederivates m it H ilfe Pyrazon- abbauender B akterien Enzymatic Form ation of a cis,cis-Muconic Acid D erivative Using Pyrazon-D egrading Bacteria  
 Abstract    The cis,cis-muconic acid derivative of pyrazon, which was formerly isolated from the medium of pyrazon-de-grading bacteria, was formed enzymatically by incubation of the catechol derivative of pyrazon with partially purified ortho pyrocatechase from pyrazon-degrading bacteria. 
  Reference    (Z. Naturforsch. 31c, 756 [1976]; eingegangen am 6. September 1976) 
  Published    1976 
  Keywords    Pyrazon, Herbicide, Microbial Degradation, Muconic Acid Derivative, ortho-Cleavage 
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 TEI-XML for    default:Reihe_C/31/ZNC-1976-31c-0756_n.pdf 
 Identifier    ZNC-1976-31c-0756_n 
 Volume    31 
36Author    A. TrebstRequires cookie*
 Title    Inhibition of Photosynthetic Electron Flow by Phenol and Diphenylether Herbicides in Control and Trypsin-Treated Chloroplasts  
 Abstract    Alkyl substituted 2-halogen-4-nitro-phenols (like brom onitrothymol) are potent inhibitors of photosynthetic electron flow in chloroplasts. There inhibition site is identical to that of DCMU, though the phenols do not contain th eir essential chemical elem ent responsible for inhibition nor do they follow their correlation of chemical structure and biochemical function. Binding of labelled m etribuzin on the chloroplast m em brane and its replacem ent by the phenol inhibitors support the notion of identical binding sites, however. In trypsin treated chloroplasts, the prim ary acceptor of photosystem II becomes accessible to ferricyanide, whose photoreduction is therefore DCMU insensitive. A fter trypsin treatm ent also the sensitivity of ferricyanide reduction to phenol inhibitors is lost as is the binding of labelled m etri­ buzin. The dinitrophenylethers of brom onitrothym ol and of ioxynil and other diphenylethers are potent inhibitors of photosynthetic electron flow. T heir site of inhibition is after the function of plasto-quinone, i. e. they are DBMIB analogues. 
  Reference    Z. Naturforsch. 34c, 986 (1979); received May 26 1979 
  Published    1979 
  Keywords    Photosynthesis, Herbicides, Trypsin Treatm ent, Brom onitrothymol, Ioxynil, Diphenylether 
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 TEI-XML for    default:Reihe_C/34/ZNC-1979-34c-0986.pdf 
 Identifier    ZNC-1979-34c-0986 
 Volume    34 
37Author    M. D. Arie-Jose, ElrieuRequires 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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 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-0347.pdf 
 Identifier    ZNC-1984-39c-0347 
 Volume    39 
38Author    J.Dirk Naber, JackJ S Van RensenRequires cookie*
 Title    Activity of Photosystem II Herbicides Is Related with Their Residence Times at the D 1 Protein  
 Abstract    The reversible binding kinetics o f atrazine, diuron and ioxynil were measured via their bind­ ing and release parameters during steady state inhibition o f electron transport. The parameters were determined in isolated chloroplasts o f peas and o f triazine-resistant and -susceptible bio­ types o f Chenopodium album using a kinetic model. This model is based on the flash-induced oxygen evolution patterns o f isolated broken chloroplasts. It was found that the binding parameters were always significantly higher in the case o f an oxidized acceptor quinone complex as compared with a semi-reduced complex. Triazine resist­ ance seems to originate from a significant increase o f the release kinetics. The release parame­ ters could be used to calculate the residence times o f the herbicides at the D 1 protein. The values o f these residence times were always much higher for the herbicides than for Q B; this explains the inhibition o f electron transport. The only exception was the residence time o f atra­ zine in the resistant biotype, where the value was close to that o f Q B. It is concluded that the "on" kinetics o f a com pound to its binding environment at the D 1 protein are determined principally by the accessibility o f the niche to the com pound. The dif­ ferences in activity between herbicides are mainly due to variations in the release kinetics. 
  Reference    Z. Naturforsch. 46c, 575—5 (1991); received March 18 1991 
  Published    1991 
  Keywords    Chloroplasts, Photosystem II, D 1 Protein, Herbicides, Triazine Resistance 
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 TEI-XML for    default:Reihe_C/46/ZNC-1991-46c-0575.pdf 
 Identifier    ZNC-1991-46c-0575 
 Volume    46 
39Author    Barbara Schaller, Bernd Schneider, HorstRobert SchütteRequires cookie*
 Title    Metabolism of the Herbicide Bromoxynil in Hordeum vulgare and Stellaria media  
 Abstract    The metabolism of [3,5-14C]3,5-dibromo-4-hydroxybenzonitrile (bromoxynil) was studied in Hordeum vulgare and Stellaria media. In excised barley seedlings the time course of metabolism was followed over 48 h and the distribution of radioactivity to various metabolic fractions measured. The metabolites, sepa­ rated by TLC and HPLC, were identified by chemical and spectrometric methods. Bromo-hydroquinone and 2,6-dibromohydroquinone were found, indicating partly debromination and replacement of the nitrile group by hydroxyl. The major parts of bromoxynil and of the metabolites were recovered in glucosidic conjugates. In Stellaria media the same metabolites as in Hordeum vulgare were determined. Additional­ ly, metabolites of unknown structures without bromine were detected. 
  Reference    Z. Naturforsch. 47c, 126—131 (1992); received June 18/August 21 1991 
  Published    1992 
  Keywords    Herbicide, Bromoxynil, Metabolites, Structural Elucidation, Hordeum vulgare, Stellaria media 
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 TEI-XML for    default:Reihe_C/47/ZNC-1992-47c-0126.pdf 
 Identifier    ZNC-1992-47c-0126 
 Volume    47 
40Author    Sophie Creuzet, TeresaM. Iranda, Jean-M Arc DucruetRequires cookie*
 Title    Comparison of Experimental and Calculated Hydrogen Bonding Properties of Some Urea and Triazine Inhibitors of Photosystem II  
 Abstract    Previous studies o f structure/activity relationships o f photosystem II inhibitors, including com parisons o f their inhibitory power in herbicide-resistant and susceptible chloroplasts, have led to predict the role o f hydrogen bonding, associated to hydrophobicity, in the binding onto the Qb site. The crystallographic structures o f bacterial reaction centers now allow these bonds to be identified. In order to be able to understand the binding o f various herbicides and the effects o f resistance mutations within the Q B site, a reliable estimation o f hydrogen bonding strengths is needed. We show here, by calculating interactions with model com pounds, con ­ trolled by physicochemical measurements, that the hydrogen bonding properties o f the C = X nucleophilic moiety present in most PS II inhibitors are different for triazines as compared to urea or amide derivatives. Semiempirical methods (AM 1) fail to reproduce the energies o f hy­ drogen bonds between a triazine ring nitrogen and a phenolic proton. An empirical method (SI BFA), designed to reproduce interaction energies, has been adapted with the aim o f calculat­ ing the binding energies o f various herbicides with models o f the Q B site. 
  Reference    Z. Naturforsch. 48c, 179 (1993); received November 12 1992 
  Published    1993 
  Keywords    Herbicide, Herbicide Resistance, Hydrogen Bonding, M olecular Calculation, Photosystem II 
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 TEI-XML for    default:Reihe_C/48/ZNC-1993-48c-0179.pdf 
 Identifier    ZNC-1993-48c-0179 
 Volume    48 
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