Indoleacetic Acid in Cambial Tissue of Radiata Pine

Abstract

The major growth substance detected by mesocotyl bioassay in extracts from cambial tissue of mature radiata pine (Pinus radiata D. Don) was identified as indoleacetic acid by movement on chromatograms and electrophoretograms, by Salkowski test, and by absorption and fluorescence spectroscopy. Indoleacetic acid concentration increased in the top stem in late winter and in the mid and lower stem in mid-spring, consistent with auxin moving down the stem at this time. Since material chromatographically similar to indoleacetic acid was not formed when [14C]tryptophan was added to the extracting medium, the indoleacetic acid was not formed by oxidation of tryptophan during extraction.