Auxin is a hormone essential for plant growth and development that affects many areas of development including root development, gravitropic and phototropic responses. The auxin-resistant4 (axr4) mutant of Arabidopsis is characterized by auxin-resistant roots with reduced lateral root growth and gravitropic response. The auxin importer AUX1 protein is mislocalized in axr4 mutants indicating that the AXR4 protein, localized to the endoplasmic reticulum, is necessary for proper AUX1 localization and regulates its function in membrane trafficking. The exact function of AXR4 remains unknown but this research shall help determine the function. Several putative enhancers of axr4-3 were isolated and characterized. Three enhancers that are more auxin resistant than axr4-3 and are inherited in an auxin sensitive, recessive manner were further analyzed. Root growth assays indicate the enhancers are more resistant than axr4-3 to 2,4-dichlorophenoxyacetic acid (2,4-D) and indole-3-acetic acid (IAA) but are sensitive to the diffusible naphthaleneacetic acid (1-NAA). The enhancers also demonstrate reduced lateral root formation and defective gravitropic responses. Three alleles of axr4 and the enhancers have reduced auxin influx The enhancers appear to affect the same responses as axr4-3 and further characterization of these enhancer lines will provide a better understanding of AXR4 and auxin transport.