Graduate Thesis Or Dissertation
 

Effects of lactofen herbicide on cellular uptake of glyphosate herbicide in malva parviflora L.

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/w3763907z

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  • Time-course growth chamber studies were conducted on little mallow (Malva parviflora L.) to determine whether sublethal doses of lactofen (1'-(carboethoxy)ethyl-5-[2-chloro-4-(trifluoromethyl) phenoxy]-2- nitrobenzoate) would enhance uptake of glyphosate (N'-(phosphonomethyl) glycine) by altering membrane permeability. Lactofen-induced membrane peroxidation was determined by harvesting leaf discs, measuring stress ethylene evolution, and recording increases in electrical conductivity. Sublethal doses were established by determining the point at which stress ethylene was evolved, but increases in electrical conductivity were not significant; dosages above this point caused significant disruption of membrane integrity. Because shikimate accumulation requires biochemically active cells and shikimic acid concentration is directly correlated with glyphosate dose, glyphosate entry into cells was determined by measuring increases in shikimic acid content over time. By 84 h after application, shikimate accumulation in little mallow increased three- to four-fold when sublethal doses of lactofen were added to glyphosate spray solutions compared with glyphosate alone. Because light-activation of lactofen was not required, enhancement of cellular uptake of glyphosate was not attributed to subtle membrane perturbations induced by the peroxidative mechanism of action of sublethal lactofen doses. The absence of thick epicuticular wax deposits on little mallow leaf surfaces was revealed by scanning electron microscopy. Abrading cuticles physically did not enhance shikimate levels when glyphosate was applied alone or in combination with lactofen. The cuticle therefore was not a significant barrier to glyphosate uptake in little mallow grown under conditions of these experiments. The enhancing effect of lactofen on cellular uptake of glyphosate occurred at the cellular level but was not due to the normal light-activated mechanism of lactofen action.
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