Distribution of diclofop‐methyl and metabolites in oat (Avena sativa L.) protoplasts

Abstract

The metabolism of the herbicide diclofop-methyl and the distribution of it and its metabolites have been investigated in a system utilizing isolated oat protoplasts {Avena sativa L. 'Cascade')-Accumulations of '''C-diclofop-methyl were found in membrane fractions of the protoplasts. Diclofopmethyl partitioned into the lipid phase of the protoplast plasma membrane. Comparatively small amounts of diclofop were found associated with the protoplasts. Diclofop-methyl was converted to diclofop in the treatment solution by hydrolytic enzymes associated with the external surface of the protoplast. Approximately 78% of the radiolabel recovered from the treatment solution was diclofop. The two major accumulations of radiolabel were found in the water insoluble portion (membrane fraction) of the protoplast as diclofop-methyl and in the treatment solution as diclofop. Verteilung von Diclofop-methyl und Metaboliten in Hafer-(A\tn& sativa L.)-ProtoplastenDer Abbau von '''C-markiertem Diclofop-methyl und die Verteilung des Wirkstoffs sowie eines Metaboliten wurden in isolierten Protoplasten von Hafer {Avena sativa L. 'Cascade') untersucht. Der Wirkstoff war in den Protoplastenmembranen angereichert, wobei eine Anlagerung an die Lipidphase der Plasmamembran festgestellt wurde. Von Diclofop waren vergleichsweise geringe Mengen an die Protoplasten gebunden. Diclofop-methyl wurde in der Versuchslosung dureh hydrolytische Enzyme, die an der Protoplastenaussenflache lagen, zu Diclofop umgewandelt. Radioaktiv markierte Stoffe wurden hauptsachlich als Diclofop-methyl am Protoplastenmembransystem und als Diclofop (mit 78% der eingebrachten '''C-Aktivitat) in der Losung gefunden.

Fatty-acid biosynthesis and acetyl-coa carboxylase as a target of diclofop, fenoxaprop and other aryloxy-phenoxy-propionic acid herbicides

“…uptake and distribution within the plant) [1][2][3][4][5][6], their freeacid forms seem to represent the actual active ingredient. In fact, for some diphenoxy-propionic acid type herbicides it was shown that the applied esters are fast hydrolyzed within the plant cell to the free acids [33]. Similar results as described here for Avena chloroplasts, were also found for diclofop and fenoxaprop using maize chloroplasts [10].…”

Evidence Against a Direct Membrane Effect in the Mechanism of Action of Graminicides

“…The aryloxyphenoxypropionates are applied as esters but are rapidly converted to the active acid form of the herbicide (21,30). This esterification reaction presumably oc curs extracellularly (33). Following movement across the cell membrane, the graminicides are translocated to the meristematic regions.…”

Carboxylesterase activities toward pesticide esters in crops and weeds

“…Esterase activities toward the herbicides were significantly higher in the weeds than in wheat, most markedly with the AOPP herbicide diclofop-methyl. The respective enzymes have been shown to be expressed in the apoplast in both wild oat (Holl et al, 1986) and wheat (Haslam et al, 2001) and have recently been identified and cloned from black-grass (Cummins and Edwards, 2004). Based on sequence analysis, the 40 kDa esterase from black-grass showed homology to a large group of ill-characterised hydrolases found in micro-organisms and plants termed the GDSL lipases (Brick et al, 1995).…”