Maintenance of Polarity of Auxin Movement by Basipetal Transport

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Abstract
The aerobic basipetal transport of indoleacetic acid (IAA) in coleoptiles of Avena sativa reduced the acropetal diffusion of IAA. In all experiments, sections of coleoptiles took up C14 carboxyl labelled IAA anaerobically and all had a similar distribution of diffusing auxin. After uptake, the sources of IAA were removed and half the sections were transferred to air to allow transport to begin; the rest were kept anaerobic. When basipetal transport was totally inhibited by anaerobic conditions, movement of auxin was nonpolar and proceeded either basipetally or acropetally depending on the existing concentration gradient. When air was readmitted, basipetal transport resumed within 15 minutes; and the acropetal movement decrease equalled the increase in basipetal movement.