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'Herbicides' in keywords Facet   section ZfN Section C:Volume 034  [X]
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1979 (6)
1Author    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 
2Author    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 
3Author    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 
4Author    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 
5Author    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 
6Author    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