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 −8 M or higher inhibited growth of emersed parrotfeather ( Myriophyllum brasiliense Camb.). There was little acropetal movement after applications of 1.1 × 10 −5 M 2,4-D-1- 14 C to the roots of emersed parrotfeather. When the metabolic inhibitor dinitrophenol at concentrations of 10 −3 or 10 −4 M was root-applied concomitantly with 10 −8 M 2,4-D-1- 14 C, 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- 14 C to mature leaves in the shoot center of emersed parrotfeather.