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1Author    MarcelA K Jansen, ChristoM. Alan, Yoseph Shaaltiel, Jonathan GresselRequires cookie*
 Title    Mode of Evolved Photooxidant Resistance to Herbicides and Xenobiotics  
 Abstract    A few species have evolved resistance to paraquat after repeated selection. As paraquat still inhibited N A D P reduction, we hypothesized that resistance might be due to (a) detoxification o f the paraquat-generated active oxygen species and (b) that resistant plants would have some cross resistance to other xenobiotic oxidants as well as to photoinhibition, which we subse­ quently demonstrated. The levels o f plastid isozymes o f the oxygen detoxification pathway: (CuZn) superoxide dismutase, ascorbate peroxidase and glutathione reductase were genetical­ ly higher in the resistant than in the sensitive biotype o f C onyza bonariensis through the F2 generation. Resistance was suppressed by chelators o f copper and/or zinc. Intact chloroplasts from resistant plants had less membrane damage with and without paraquat, than those from sensitive plants. Resistant C onyza plants recover from paraquat inhibition o f photosynthesis in 3 -4 h in high light, whereas sensitive plants died. Both resistant and sensitive plants recov­ ered from paraquat in 3 -4 h in low light intensities. Paraquat-resistant Conyza plants were cross-tolerant to S 0 2, atrazine, acifluorfen and to photoinhibition. Drought-tolerant maize inbreds were cross-tolerant to paraquat, SO, and acifluorfen (compared to sensitive lines) and they also possessed higher levels o f (Cu/Zn) superoxide dismutase and glutathione reductase. The tolerance to oxidant stresses in C onyza and maize increases with plant age, suggesting that the shift to resistance is a constitutive, earlier expression o f the genes normally expressed later in development. 
  Reference    Z. Naturforsch. 45c, 463 (1990); received November 9 1989 
  Published    1990 
  Keywords    Paraquat, Acifluorfen, Atrazine, Photoinhibition, Superoxide Dismutase 
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 TEI-XML for    default:Reihe_C/45/ZNC-1990-45c-0463.pdf 
 Identifier    ZNC-1990-45c-0463 
 Volume    45