Many of the synthetic auxins (artificially produced) like 204D (2-4 dichlorophenoxy acetic acid) are selective weed killers and are employed in fields. 2-4D kills broad leaved plants, while it is relatively ineffective against narrow leaved ones. Hence 2-4D can be used to kill dicotyledonous weeds in a field with monocotyledonous crops. It has been demonstrated that 2-4D increases carbohydrate metabolism (by increased rate of respira­tion) so that plants die due to exhaustion of nutrients. Another advantage of 2-4D is, it is less toxic to animals and human beings.