ABSORPTION AND TRANSLOCATION OF GLUFOSINATE ON 4 WEED SPECIES

Greenhouse and laboratory experiments were conducted to evaluate folia r absorption, translocation, and efficacy of glufosinate on four weed species. The rare of glufosinate required to reduce shoot dry weight b y 50% (GR(50)) varied between weed species. GR(50) values for giant fo xtail, barnyardgrass, velvetleaf, and common lambsquarters were 69, 18 6, 199, and 235 g ai ha(-1), respectively. Absorption of C-14-glufosin ate increased with time and reached a plateau 24 hours after treatment (HAT). Absorption of C-14-glufosinate was 67, 53, 42, and 16% for gia nt foxtail, barnyardgrass, velvetleaf, and common lambsquarters, respe ctively. Translocation of absorbed C-14-glufosinate from the treated l eaf was greatest for giant foxtail and barnyardgrass (15 and 14% 24 HA T of absorbed C-14-glufosinate, respectively). This compared to 5 and < 1% for translocation of absorbed C-14-glufosinate from the treated l eaves of velvetleaf and common lambsquarters. The majority of C-14-glu fosinate translocated by giant foxtail and barnyardgrass was found bel ow the treated leaf and in the roots, indicating phloem mobility of th e herbicide. Differential absorption and translocation of C-14-glufosi nate may be contributing factors to the differential sensitivity obser ved between weed species.