Greenhouse studies were conducted to evaluate absorption, translocation, and metabolism of 14C-glufosinate in glufosinate-resistant cotton, nontransgenic cotton, Palmer amaranth, and pitted morningglory. Cotton plants were treated at the four-leaf stage, whereas Palmer amaranth and pitted morningglory were treated at 7.5 and 10 cm, respectively. All plants were harvested at 1, 6, 24, 48, and 72 h after treatment (HAT). Absorption of 14C-glufosinate was greater than 85% 24 h after treatment in Palmer amaranth. Absorption was less than 30% at all harvest intervals for glufosinate-resistant cotton, nontransgenic cotton, and pitted morningglory. At 24 HAT, 49 and 12% of radioactivity was translocated to regions above and below the treated leaf, respectively, in Palmer amaranth. Metabolites of 14C-glufosinate were detected in all crop and weed species. Metabolism of 14C-glufosinate was 16% or lower in nontransgenic cotton and pitted morningglory; however, metabolism rates were greater than 70% in glufosinate-resistant cotton 72 HAT. Intermediate metabolism was observed for Palmer amaranth, with metabolites comprising 20 to 30% of detectable radioactivity between 6 and 72 HAT.
Nomenclature: Glufosinate; Palmer amaranth, Amaranthus palmeri S.Wats. AMAPA; pitted morningglory, Ipomoea lacunosa L. IPOLA; cotton, Gossypium hirsutum L.