Metabolism of Indole-3-acetic Acid

Abstract

The biological activity of 20 L-.alpha.-amino acid conjugates of IAA to stimulate cell elongation of Avena sativa coleoptile sections and to stimulate growth of soybean [Glycine max] cotyledon tissue cultures was examined at concentrations of 10-4 to 10-7 M. In the Avena coleoptile test most of the amino acid conjugates stimulated elongation. Several of the conjugates stimulated as much elongation as IAA, but their half-maximum concentrations tended to be higher. Some of the more active conjugates were alanine, glycine, lysine, serine, aspartic acid, cystine, cysteine, methionine and glutamic acid. In the soybean cotyledon tissue culture test all of the L-.alpha.-amino acid conjugates of IAA stimulated growth except for the phenylalanine, histidine and arginine conjugates. Most of the conjugates produced responses at least as great as that caused by IAA. Conjugates with half-maximum concentrations lower than IAA included cysteine, cystine, methionine and alanine. These conjugates exceed the IAA-induced callus growth at all tested concentrations. Other conjugates significantly better than IAA at 10-6 M were serine, glycine, leucine, proline and threonine.