ON THE MANNER OF TRIIODOBENZOIC ACID INHIBITION OF AUXIN TRANSPORT

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Abstract
The effects of 2, 3, 5-triiodobenzoic acid on the transport of indoleacetic acid by corn coleoptile sections were examined relative to the entry and exit components of the transport system. The TIBA inhibition of IAA entry was found to be relatively weak, requiring about 1,000-fold higher concentrations than the inhibition of exit. The preferential inhibition of exit can account for the accumulation of IAA in TIBA-inhibited tissue sections. The kinetics of the TIBA inhibitions indicate markedly different characteristics of the entry and exit components, and implicate exit as a rate-limiting step in the auxin transport mechanism.