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Published online by Cambridge University Press: 12 June 2017
Experiments were conducted on poison ivy (Rhus radicans L.) to determine the effect of auxin on the formation of sprouts. Stump sprouting occurred where poison ivy propagules were decapitated. The influence of the shoot could be replaced by applying indoleacetic acid (hereinafter referred to as IAA) in lanolin paste to the cut surface of the stump. When the paste was removed after inhibiting stump sprouting for a month, sprouts formed within 35 days. This evidence supports the apical dominance theory of stump sprouting. When IAA-2-14C in lanolin was applied to the cut surface of the root stump, autoradiographs showed that 14C activity was concentrated where the majority of stump sprouts would develop, and chromatography of an extract indicated the presence of an auxin oxidation product of IAA. Dialyzed enzyme preparations from poison ivy stumps oxidized IAA in a Warburg apparatus which demonstrated that an IAA oxidizing system was present.