Studies on phloem exudation from Yucca flaccida Haw. X. Translocation of indole-3-acetic acid

An investigation was made whether indoleacetic acid-1-l4C can be translocated through the phloem of segments of the apical part of the young inflorescence of Yucca flaccida Haw. The radioactivity in phloem exudate from wounds was used as a criterium for translocation. A polar movement (more upwards than downwards) could be observed during the first hours of the experiments; later the concentration of 14C in the exudate became equal in both directions. The relative radioactivity of the exudate was much lower with indoleacetic acid than with substances that are readily translocated through the phloem, e.g., sucrose or maleic hydrazide. Thin-layer chromatography of the exudate showed the presence of two major radioactive metabolites different in Rf from indoleacetic acid and an almost complete absence of indoleacetic acid itself.