Uptake and Translocation of 2,4-D-1-14C in Parrotfeather

Root applications of (2,4-dichlorophenoxy)acetic acid (2,4-D) at concentrations of 2.5 × 10−8M or higher inhibited growth of emersed parrotfeather (Myriophyllum brasiliense Camb.). There was little acropetal movement after applications of 1.1 × 10−5M 2,4-D-1-14C to the roots of emersed parrotfeather. When the metabolic inhibitor dinitrophenol at concentrations of 10−3 or 10−4M was root-applied concomitantly with 10−8M 2,4-D-1-14C, there was an acropetal movement of radioactivity in the transpiration stream to the plant shoot. Basipetal movement occurred in the phloem after applications of 2.2 μg 2,4-D-1-14C to mature leaves in the shoot center of emersed parrotfeather.