A Microautoradiographic Study of Auxin Transport in the Stem of Intact Pea Seedlings (Pisum sativumL.)

Abstract

Soluble-compound microautoradiography was used to determine the distribution of radioactivity in transverse sections of intact dwarf pea stems (Pisum sativum L.) following the application of [³H]IAA to the apical bud. Near the transport front label was confined to the cambial zone of the axial bundles, including the differentiating secondary vascular elements. Fully differentiated phloem and xylem elements remained unlabelled and no radioactivity was detected in the leaf or stipule traces. Similar results were obtained in experiments with Vicia faba L. plants. Nearer the labelled apical bud of the pea there was a more general distribution of label and evidence was found of free-space transport of radioactive material in the pith.