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1991 (1)
1982 (1)
1980 (1)
1Author    DonaldE M Oreland, FrederickT. CorbinRequires cookie*
 Title    Influence of Safeners on the in vivo and in vitro Metabolism of Bentazon and Metolachlor by Grain Sorghum Shoots: a Preliminary Report  
 Abstract    Metabolism of bentazon and m etolachlor by excised shoots and a microsomal fraction iso­ lated from the shoots, of 3-day-old, dark-grown, grain sorghum (Sorghum bicolor cv. Funk G 522 DR) seedlings was studied. The effects of seed treatments, on the subsequent m etabo­ lism of the herbicides, with the safeners naphthalic anhydride, oxabetrinil, and CGA 133205 were compared against surface-sterilization and Captan-treatm ents. Bentazon was aryl hydroxylated in both in vivo and in vitro studies with the hydroxylated derivative undergoing glycosylation only under in vivo conditions. Both shoots and microsomes isolated from shoots of safener-treated seed showed enhanced metabolism of bentazon relative to the controls. In­ hibition by tetcyclacis, a potent inhibitor of plant cytochrome P-450 monooxygenases, in both the in vivo and in vitro studies, and a requirement for N A DPH in the in vitro studies suggested that the formation of hydroxybentazon was mediated by a cytochrome P-450 monooxygenase. Metolachlor was metabolized to polar material and O-desmethylmetolachlor under in vivo conditions. Only the demethylated product was formed in vitro. Shoots isolated from safener-treated seed showed enhanced form ation o f polar com pounds which were assumed to have arisen from conjugation with glutathione. Tetcyclacis did not affect the formation of the polar components. However, the form ation of O-desmethylmetolachlor was depressed in the shoots excised from safener-treated seed under both in vivo and in vitro conditions. Tetcyclacis com ­ pletely prevented form ation of the demethylated metabolite. Hence, formation of this m eta­ bolite is considered to be P-450 mediated. The differential response obtained with the safeners, i.e., stimulation of aryl hydroxylation o f bentazon and depression of metolachlor demethyla-tion, suggests that the reactions are probably catalyzed by different cytochrome P-450 m ono­ oxygenases. 
  Reference    Z. Naturforsch. 46c, 906—914 (1991); received M arch 26 1991 
  Published    1991 
  Keywords    Microsomes, Metolachlor, Bentazon, Cytochrome P-450, Mixed Function Oxidase 
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 TEI-XML for    default:Reihe_C/46/ZNC-1991-46c-0906.pdf 
 Identifier    ZNC-1991-46c-0906 
 Volume    46 
2Author    D. Meier, H. K. Lichtenthaler, G. BurkardRequires cookie*
 Title    Change of Chloroplast Ultrastructure in Radish Seedlings under the Influence of the Photosystem II-Herbicide Bentazon  
 Abstract    The influence of the photosystem II-herbicide bentazon on the ultrastructure o f chloroplasts o f radish seedlings (Raphanus sativus L.) was investigated with special emphasis on thylakoid developm ent and grana formation. Bentazon application (10-3 m) induces the formation of broader and higher grana stacks (grana width: 0 .5 -0 .6 n m ; greatest frequency: 3 -8 thylakoids per granum) than in the control plants (grana width: 0.3 |im; greatest frequency: 2 -4 thylakoids per granum). Furtherm ore, the am ount of chloroplast lamellae is enhanced, as are the stacking degree of thylakoids and the grana area. The chloroplasts of bentazon-treated plants appear to be shorter and thicker than in the controls and show all signs of a shade-type adaptation of the photosynthetic apparatus. 
  Reference    Z. Naturforsch. 35c, 656 (1980); received March 17 1980 
  Published    1980 
  Keywords    Bentazon, Chloroplast-Ultrastructure, G rana Form ation, Photosystem II-Herbicide, Shade-type Chloroplasts 
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 TEI-XML for    default:Reihe_C/35/ZNC-1980-35c-0656.pdf 
 Identifier    ZNC-1980-35c-0656 
 Volume    35 
3Author    H. K. Lichtenthaler, D. M. Eier, G. Retzlaff, R. HammRequires cookie*
 Title    Distribution and Effects of Bentazon in Crop Plants and Weeds  
 Abstract    The inhibition of photosynthetic C 0 2-assimilation and o f the variable chlorophyll fluorescence as well as uptake and transport of 14C-labelled bentazon and the possibilities for a herbicide-induced shade-type modification of the photosynthetic apparatus were investigated in bentazon-sensitive weeds (Galium, Sinapis, Raphanus) and in the tolerant crop plants wheat and maize. 1. In weeds the depression o f photosynthetic C 0 2-assimilation is irreversible, whereas tolerant plants recover due to the metabolization o f the active herbicide. 2. A lower rate of uptake and transport o f bentazon associated with its fast metabolization is the reason for the tolerance o f crop plants towards bentazon. 3. The transport of [l4C]bentazon proceeds in the tracheary elements of the xylem. Uptake and transport of bentazon in the weeds are light dependent. 4. The loss o f variable fluorescence (Kautsky effect) in the leaves after root application o f bentazon proceeds much faster at high-light than at low light conditions and confirms the light-dependency of the bentazon transport. 5. In the sensitive dicot weeds bentazon not only inhibits photosynthetic electron flow and depresses C 0 2-fixation but also induces the formation o f shade-type chloroplasts which are less efficient in photosynthetic quantum conversion. This bentazon-induced modification of the photosynthetic apparatus (e.g. changes in ultrastructure, pigment ratios, and levels o f chloro-phyll-proteins) contributes to the effectiveness o f bentazon as a herbicide. 
  Reference    Z. Naturforsch. 37c, 889—8 (1982); received July 9 1982 
  Published    1982 
  Keywords    Bentazon, C 0 2-Assimilation, Inhibition of Photosynthesis, Photosystem 2-Herbicide, Shade-Type Adaptation of Chloroplasts 
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 TEI-XML for    default:Reihe_C/37/ZNC-1982-37c-0889.pdf 
 Identifier    ZNC-1982-37c-0889 
 Volume    37