Basis for the selective action of fluroxypyr

Abstract

Summary: Résumé: Zusammenfassung The dose‐response, foliar uptake, translocation and metabolism of the methylheptyl ester (MHE) of fluroxypyr were examined in lambs‐quarters (Chenopodium album L.), wild buckwheat (Polygonum convolvulus L.), Canada thistle (Cirsium arvense L. Scop.) and field bindweed (Convolvulus arvensis L.). Under controlled environment growth room conditions, E50 values, determined from shoot dry weights of the susceptible species, wild buckwheat (16 g ha−1) and field bindweed (40 g ha−1), were markedly different than those of the tolerant species, lambsquarters (331 g ha−1) and Canada thistle (800 g ha−1). Regardless of species, more than 80% of applied [14C]fluroxypyr‐MHE was absorbed by foliar surfaces 120 h after treatment. Translocation of radioactivity out of the treated leaves of susceptible species was significantly greater than that of tolerant species. For example, 120 h after treatment with [14C]‐fluroxypyr‐MHE, the proportion of applied radioactivity translocated in tolerant Canada thistle and lambsquarters was 15 and 10%, respectively, whereas in susceptible wild buckwheat and field bindweed it was 41 and 40% of applied radioactivity, respectively. High‐performance liquid chromatography (HPLC) of plant extracts indicated four distinct chroma‐tographic peaks common to all four species. More fluroxypyr was recovered in the susceptible species (70%) than in the tolerant species (30%), 120 h after application. Selectivity differences between the tolerant and susceptible species may be the result of enhanced metabolic transformation of the herbicide to more polar, non‐phytotoxic compounds with limited mobility within the tolerant species. Les bases de la sélectivité du fluroxypyr La courbe dose effet, la pénétration foliaire, la migration et le métabolisme de Tester méthyle‐heptyle (MHE) du fluroxypyr ont étéétudiés chez le chénopode blanc (Chenopodium album L.), la renouée faux‐liseron (Polygonum con‐vulvulus L.), le chardon des champs (Cirsium arvense L. Scop.) et le liseron des champs (Convolvulus arvensis L.). En conditions de crois‐sance contrôlées, les valeurs ED50, déterminées à partir du poids de matière sèche des parties aériennes étaient nettement différentes chez les plantes sensibles et chez les plantes résistan‐tes:renouée faux‐liseron, 16 g ha−1; liseron des champs, 40 g ha−1; chénopode blanc, 331 g ha−1; chardon des champs, 800 g ha−1. Quelle que soit 1'espèce, plus de 80% du [14C]fluroxypyr‐MHE pénétrait dans les feuilles en 120 h. La migration de la radioactivité hors des feuilles traitérs était significativement plus importante chez les plantes sensibles que chez les plantes tolérantes. Par exemple, 120 h après le traite‐ment avec du [14C]fluroxypyr‐MHE, la proportion de radioactivité appliquée qui avait migré dans le chardon des champs et le chénopode, tolérants, était respectivement 15 et 10%, alors que chez la renouée faux‐liseron et le liseron des champs, sensibles, elle était respectivement 41 et 40%. Des analyses par HPLC des extraits de plantes montraient qua...

A Contribution to the Elucidation of the Reduction Mechanism of 2-Chloroisonicotinic Acid on Mercury Electrodes

“…4 Clopyralid is a pre-and postemergent translocation herbicide in sunflowers, cereals, and sugar beets. 5 Fluroxypyr is a translocation herbicide easily absorbed by leaves 6 with a half-life in soil of up to 2 months. Degradation of such herbicides in the environment takes place mainly by microbial activity.…”