Description; Application; 4-Chlorophenoxyacetic acid has been used in para-chlorophenoxyacetic acid (p-CPA) residue assay.; 4-chlorophenoxy acetic acid (4-CPA), a chlorine derivative of phenoxyacetic acid (PA), is a plant growth regulator used as a herbicide.; Biochem/physiol Actions; 4-Chlorophenoxyacetic acid is a synthetic auxin, that is used to induce parthenocarpic ovary growth on flowers of wild type plants.