2 results
Dissipation and Water Activation of UCC-C4243
- Terry R. Wright, Alex G. Ogg, Jr., E. Patrick Fuerst
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- Journal:
- Weed Science / Volume 43 / Issue 1 / March 1995
- Published online by Cambridge University Press:
- 12 June 2017, pp. 149-155
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Field experiments were conducted in 1992 and 1993 to determine the timing and amount of rainfall required to activate UCC-C4243 applied preemergence. UCC-C4243 at 0, 70, and 140 g ai ha−1 was applied 1, 7, 14, and 21 d before 0.5 or 2 cm of simulated rainfall. Temporary rainshelters protected field plots from natural rainfall during the 21 d dry period. Herbicide activity was determined in the field by seeding lentil, wheat, common lambsquarters, and field pennycress and in the greenhouse by a sugarbeet bioassay of soil samples (0 to 3 cm depth) taken from all plots immediately before irrigation. UCC-C4243 did not injure wheat; however, lentil population was reduced when simulated rainfall occurred within 7 d after application. Lentil injury was greater with higher herbicide rate and higher water level. UCC-C4243 at 70 and 140 g ha−1 reduced populations of both weed species by 75 and 90%, respectively, when either 0.5 or 2 cm simulated rainfall was received within 1 d after herbicide application. Weed control was reduced with a 21 d delay between herbicide application and water activation. The sugarbeet bioassay showed a linear decrease of herbicide activity over time and also with accumulated photosynthetically active radiation. After 17.9 d, herbicide activity on a dry soil surface decreased 50%. Laboratory investigations show that [14C]-UCC-C4243 on glass slides was photodegraded by near ultraviolet light (290 to 400 nm). Volatilization of 14C-labeled herbicide from glass slides was less than 5% after exposure to turbulent air for 48 h.
Herbicidal Activity of UCC-C4243 and Acifluorfen is Due to Inhibition of Protoporphyrinogen Oxidase
- Terry R. Wright, E. Patrick Fuerst, Alex G. Ogg, Jr., Ujjana B. Nandihalli, Hee Jae Lee
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- Journal:
- Weed Science / Volume 43 / Issue 1 / March 1995
- Published online by Cambridge University Press:
- 12 June 2017, pp. 47-54
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Laboratory and greenhouse studies were conducted to determine the mode of action of soil- and foliar-applied UCC-C4243. Experiments demonstrated that UCC-C4243 required light for phytotoxicity, phytotoxic symptoms were similar to inhibitors of porphyrin synthesis such as acifluorfen, and UCC-C4243 potently inhibited protoporphyrinogen oxidase. Germination and emergence of field pennycress and lentil in the dark were not affected by soil-incorporated UCC-C4243 at rates more than 10 times greater than like treatments that killed all plants in the light. Soil-incorporated UCC-C4243 required light for activity and killed seedlings within 1 d after emergence; sublethal doses caused desiccation, veinal necrosis, and leaf deformation. Field pennycress and lentil were susceptible to soil-incorporated UCC-C4243 and acifluorfen in the light, but were 5 to 93 times less sensitive to the herbicides in the dark. Wheat was not affected by either herbicide in the light or dark. Injury symptoms from UCC-C4243 applied POST to redroot pigweed were similar to symptoms from diphenyl ether and bipyridinium herbicides: rapid, light-dependent chlorophyll bleaching, desiccation, and necrosis. UCC-C4243, acifluorfen-methyl, and acifluorfen acid caused light- and concentration-dependent chlorophyll bleaching and electrolyte leakage from cucumber leaf disks (I50 = 1.0, 1.8, and 4.3 μM, respectively). An inhibitor of the porphyrin synthesis pathway, 4,6-dioxoheptanoic acid, almost completely inhibited herbicide-induced electrolyte leakage. δ-Aminolevulinic acid, a tetrapyrrole precursor and stimulator of the porphyrin synthesis pathway, caused synergistic effects with each herbicide. Protoporphyrinogen oxidase from barley etioplast preparations was inhibited 50% by 40 nM UCC-C4243. Barley leaf sections treated with 100 μM UCC-C4243 accumulated protoporphyrin IX in vivo to levels > 75 times non-treated controls. These data indicate the light-requiring herbicide activity of UCC-C4243, like acifluorfen, is due to inhibition of protoporphyrinogen oxidase.