Provide a mechanistic link between auxin and plasma membrane H(+)-ATPases (PM H(+)-ATPases, e.g. AHA1 and AHA2), and triggers PM H(+)-ATPases activity by promoting phosphorylation of their C-terminal autoinhibitory domain as a result of PP2C-D subfamily of type 2C phosphatases inhibition, thus leading to the acidification of the apoplast and the facilitation of solutes and water uptake to drive cell expansion (By similarity). Triggers plant growth probably by promoting cell elongation (By similarity). Regulates branch angles and bending (By similarity). Expressed in organ primordia (PubMed:29258424). Hardly observed in leaves (PubMed:29258424). Highly active in root primordia, leaf primordia and flower primordia. Induced by zeatin (PubMed:29258424). Repressed by abscisic acid (PubMed:29258424). Belongs to the ARG7 family.