title: Indoleacetic Acid biosynthesis in Avena coleoptile tips and excised bean shoots.
abstract: Avena coleoptiles did not elongate when incubated with tryptophan under sterile conditions. Indole, anthranilic acid, and tryptamine promoted elongation. Under the same conditions, the tissue converted tryptophan-(14)C to IAA-(14)C. More IAA-(14)C was produced from indole-(14)C than from tryptophan-(14)C; however, the free tryptophan content of the tissue was also greatly increased by the indole treatment. Tryptophan-(14)C was readily taken up by the tissue but was mainly incorporated into protein and did not increase the free tryptophan level. When bean shoots were labeled with tryptophan-(14)C or indole-(14)C, the label incorporation into IAA-(14)C was very nearly the same. In this tissue the free tryptophan level in the tryptophan-(14)C and indole-(14)C treatments was also about equal. These results suggest that failure of exogenously supplied tryptophan to promote the elongation of Avena coleoptiles is a result of its predominant incorporation into protein and consequent unavailability for conversion to IAA.
authors.affiliation: Department of Biology, The Pennsylvania State University, University Park, Pennsylvania 16802.
authors.forename: R C
authors.initials: RC
authors.lastname: Black
authors.forename: R H
authors.initials: RH
authors.lastname: Hamilton