Somed-amino acid (glutamic acid, valine, or leucine) conjugates of 2,4-dichlorophenoxyacetic acid (2,4-D) at 10−5molar, stimulated elongation ofAvena sativaL. var Mariner coleoptile sections and growth of soybean (Glycine max.L. var Amsoy) tissue as much as did thel-amino acid conjugates at 10−6molar. Thed-methionine conjugate did not stimulate growth of soybean root callus tissue but did stimulateAvenaelongation. Thed-aspartic acid conjugate did not stimulate elongation ofAvenacoleoptiles 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 [1-14C]2,4-D resulted in a greater uptake of [1-14C]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 [14C]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 preincubati