Biological Properties of d-Amino Acid Conjugates of 2,4-D 1

Some d -amino acid (glutamic acid, valine, or leucine) conjugates of 2,4-dichlorophenoxyacetic acid (2,4-D) at 10 −5 molar, stimulated elongation of Avena sativa L. var Mariner coleoptile sections and growth of soybean ( Glycine max. L. var Amsoy) tissue as much as did the l -amino acid conjugates at 10 −6 molar. The d -methionine conjugate did not stimulate growth of soybean root callus tissue but did stimulate Avena elongation. The d -aspartic acid conjugate did not stimulate elongation of Avena coleoptiles but did stimulate growth of root callus tissue. Pretreatment of root callus tissue with 100 micromolar 2,4-D-( d ) -or ( l ) glutamic acid for 18 hours prior to incubation for 6 hours in [1- 14 C]2,4-D resulted in a greater uptake of [1- 14 C]2,4-D than did pretreatment with 2,4- d . Qualitatively the metabolites were similar in all preincubation treatments. Preincubation with 2,4-D-( d )-glutamic acid also resulted in larger free [ 14 C]2,4-D pool and a significant increase in water-soluble conjugates when compared with 2,4-D, or 2,4-D-( l )-glutamic acid preincubations.