Hydrotropism: Root Bending Does Not Require Auxin Redistribution

The widely accepted Cholodny-Went theory posits that asymmetrical auxin redistribution is required for tropic growth of plant organs. We demonstrate, using the sensitive auxin-sensor protein DII-VENUS that, in the presence and absence of auxin polar transport inhibitors, root tropism toward moisture (hydrotropism) does not involve auxin redistribution. Moreover, highly specific auxin signaling antagonists accelerate hydrotropism. Thus, hydrotropism is an exception to the Cholodny-Went theory.