John P. Chupp

Differential inhibition of anthocyanin synthesis in etiolated sorghum (Sorghum bicolor (L.) Moench) mesocotyls by rotomeric 2-halo-N-methyl-N-phenylacetamides

Abstract Stable rotomeric forms of 2-iodo- and 2-bromo- N -methyl- N -phenylacetamides were compared in their inhibitory activity against anthocyanin synthesis. Rotomers known to readily undergo nucleophilic substitution, designated the cis or minor form, were potent inhibitors of anthocyanin synthesis, whereas their relatively nonreactive counterparts, the trans or major rotomers, were inactive as anthocyanin inhibitors. I 50 estimations for inhibition of anthocyanin synthesis for the cis forms of the 2-iodo- and 2-bromo- N -methyl- N -phenylacetamides were 4 and 13 μ M , respectively. Anthocyanin inhibition by a cis rotomer was neither enhanced nor prevented by the presence of a trans rotomer. These data suggest that there is a target site for cis 2-halo- N -phenylacetamide herbicides in the pathway leading to anthocyanin synthesis.