Growth-Regulating Chemicals Persist in Plants: Qualitative Bioassay

Scions from untreated tomato plants were grafted on plants treated with 2,4-dichlorophenoxyacetic acid by dipping one leaf in a solution containing 1000 parts per million. Subsequent malformations of the scion shoot and leaves were used as criteria of the presence of this chemical. The chemical or a substance causing similar symptoms persisted in the plant in physiologically active amounts for approximately 60 days.