Comparative Degradation of [14C]-2,4-Dichlorophenoxyacetic Acid in Wheat and Potato after Foliar Application and in Wheat, Radish, Lettuce, and Apple after Soil Application

• Published in: Journal of agricultural and food chemistry 2001-01, Vol.49 (1), p.146-155
• Main Authors: Hamburg, Arlene, Puvanesarajah, Velupillai, Burnett, Thomas J, Barnekow, David E, Premkumar, Noel D, Smith, Gregory A
• Format: Article
• Language: English
• Subjects: 2,4-Dichlorophenoxyacetic Acid - administration & dosage; 2,4-Dichlorophenoxyacetic Acid - metabolism; Biodegradation, Environmental; Biological and medical sciences; Carbon Radioisotopes; Chemical control; Fruit - metabolism; Fundamental and applied biological sciences. Psychology; Herbicides - metabolism; Parasitic plants. Weeds; Phytopathology. Animal pests. Plant and forest protection; Plant Leaves; Soil; Solanum tuberosum - metabolism; Triticum - metabolism; Vegetables - metabolism; Weeds
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf000120q

The fate of 2,4-dichlorophenoxyacetic acid (2,4-D) applied foliarly as the 2-ethylhexyl ester (EHE) to wheat and potatoes, to the soil as the dimethylamine (DMA) salt under apple tree canopies, and preplant as the free acid for wheat, lettuce, and radish was studied to evaluate metabolic pathways. Crop fractions analyzed for 14C residues included wheat forage, straw, and grain; potato vine and tubers; and apple fruit. The primary metabolic pathway for foliar application in wheat is ester hydrolysis followed by the formation of base-labile 2,4-D conjugates. A less significant pathway for 2,4-D in wheat was ring hydroxylation to give NIH-shift products 2,5-dichloro-4-hydroxyphenoxyacetic acid (4-OH-2,5-D), 4-OH-2,3-D, and 5-OH-2,4-D both free and as acid-labile conjugates. The primary metabolic pathway in potato was again ester hydrolysis. 2,4-D acid was further transformed to 4-chlorophenoxyacetic acid and 4-OH-2,5-D. For the soil applications, 14C residues in the crops were low, and characterization of the 14C residues indicated association with or incorporation into the biochemical matrix of the tissue. The degradative pathways observed in wheat are similar to those characterized in other intact plant studies but differ from those in studies in wheat cell suspension culture in that no amino acid conjugates were observed. Keywords: 2,4-Dichlorophenoxyacetic acid; 2,4-D; herbicide; metabolism; wheat; potato; apple; lettuce; radish; rotational crop