Phytotoxicity of 2,4,5-T, Picloram, and Dicamba, Alone and in Mixtures in Tissue Culture

The herbicide 2,4,5-T [(2,4,5-trichlorophenoxy) acetic acid], at concentrations of 10−4and 10−6M in nutrient media, was more inhibitory to the growth of soybean (Glycine max(L.) Merr. “Acme”) tissue culture than dicamba (3,6-dichloro-o-anisic acid) or picloram (4-amino-3,5,6-trichloropicolinic acid). Dicamba (10−6and 10−8M) and 2,4,5-T (10−8M) stimulated growth of soybean tissue. Mixing equimolar solutions of 2,4,5-T + dicamba, 2,4,5-T + picloram, or picloram + dicamba at 10−4, 10−6, and 10−8M did not increase phytotoxicity over that of the most phytotoxic herbicide of the pair.