Tolerance of Birdsfoot Trefoil (Lotus corniculatus) to 2,4-D

Abstract

Translocation and metabolism of14C-2,4-D [(2,4-dichlorophenoxy)acetic acid] and effects of 2,4-D on protein synthesis were compared in ‘T–68’ (2,4-D tolerant) and ‘Viking’ (susceptible) birdsfoot trefoil (Lotus corniculatusL.) in an attempt to elucidate some tolerance mechanisms. After14C-2,4-D was applied to upper trifoliate leaves, significantly less 2,4-D was found in stems, in leaves below the treated leaves, and in roots of T–68 compared to Viking. More 2,4-D was bound to alcohol-insoluble cellular constituents of T–68 leaves, stems, and roots. When alcohol-soluble components were fractionated, slightly more14C water-soluble compounds were found in T–68, indicating further inactivation by glycosylation. No amino acid-2,4-D conjugates were found. The rate of14CO2evolution from14C-2,4-D treated seedlings in T–68 was five times that in Viking. Protein synthesis appeared to be more rapid in T–68 but the relationship to 2,4-D was not clear. In part, 2,4-D resistance in T–68 may result from its ability to inactivate 2,4-D by differential binding and conjugation and by side chain breakdown as indicated by14CO2release.