Auxin Transport in Geotropic Curvatures of a Branched Plant

Publisher Website
Google Scholar
Abstract
Immature plants from a clone of Coleus blumei were used to trace the movement of indoleacetic acid-2-C14 during the development of curvatures in branches and axis, as determined by radioassays after growth. The auxin was suppled either to defoliated stems as terminal caps of 1% IAA in lanolin or through a film on 1 leaf that was left on the upper side of the horizontal branch. In both cases the extract able, unaltered IAA was found to be disturbed in a ratio of approximately 40:60 in the upper and lower halves of the curvatures. Most of the C14 was extracted in nonvolatile degradation products of the IAA but the same 40:60 ratio held for the total radioactivity in the opposing sides of the stems when the C14 was supplied directly to the stem. The evidence supports the concept of downward transport of unaltered IAA as the basis for more rapid growth of the lower tissues in a geotropic curvature of a branch or main axis.