Abstract:Autoinhibition in polar transport of 3H-IAA from donor to receiver was demonstrated in pea ( Pisum sativum L. ) and mung bean ( Phaseolus radiatus L. ) using either classic "donor-receiver system" where unlabelled IAA was present in the receiver or using "Y" form explants where tmlabelled IAA in lanolin was applied to the cut surface of a separate side of the explants. Application of unlabelled IAA resulted in accmnulation and high rate of metabolism of SH-IAA in the labelled tissues, and these were further stimulated by prolonging the experimental period.