Absorption, Metabolism, and Translocation of 2,4-D by Honeyvine Milkweed

Abstract

Absorption of (2,4-dichlorophenoxy)acetic acid (2,4-D) by honeyvine milkweed [ Ampelamus albidus (Nutt.) Britt.] was 7.2, 9.3, and 10.9% of the applied herbicide at 1, 4, and 8 days after treatment, respectively. Addition of 1.0% v/v Tween 80 to the treatments increased absorption to 55.8, 71.3, and 78.7% at the same sampling dates. Metabolic alteration of the herbicide occurred only in the aerial portions of the plant, and this was not great enough to be considered as a means of resistance. Translocation of 2,4-D into the roots was more closely related to new root growth than to the amount of top growth. Plants with six leaves and no new root growth did not translocate 2,4-D into the root zone. Plants with the same number of leaves but with an average of five and 20 new roots translocated 2.5 and 7.7%, respectively, of the applied herbicide to the roots.