Auxinic Activity of Clomeprop and Its Hydrolytic Metabolite and Their Binding to Maize Auxin-Binding Protein

Clomeprop [2-(2, 4-dichloro-3-methyl phenoxy) propionanilide] is classified as a hormone-type herbicide, and was reported tohydrolyze to DMPA [2-(2, 4-dichloro-3-methyl phenoxy) propionic acid] in plants. Auxinic activity of clomeprop was compared with DMPA and several plant hormones to investigate whether clomeprop itself exhibit auxinic activity. Results were as follows: (1) In all the auxinic activity tests performed: maize coleoptile elongation test, mung bean slit test and ethylene production test, clomeprop exhibited lower auxinic activity than its metabolite DMPA. (2) DMPA showed higher inhibitory activity on maize and mung bean growth than clomeprop. (3) DMPA bound with the putative maize membrane-bound auxin receptor, while clomeprop did not. It can thus be concluded that clomeprop has no auxinic activity and that the metabolite DMPA is the active compound in the auxinic action.