Correlation of Root System Growth and Auxin Signaling

<p>Graphical presentation of a model explaining the opposite root system phenotypes of <i>hy5</i> and <i>hy5 hyh</i> mutants. The strength of (constitutive) auxin signaling in the respective genotype determines the extent of root system growth. Root system growth is maximal at a certain optimum auxin signaling level but decreases if this level is either lower or higher. This assumption is supported by the phenotypic response of wild-type seedling root systems to the external application of increasing amounts of auxin: whereas low auxin concentrations promote root system growth, high concentrations inhibit growth.