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 (PubMed:29258424). Regulates branch angles and bending (PubMed:29258424). Expressed in etiolated hypocotyls, cotyledons, leaves, flowers and siliques. In flowers, present in petals, stamen, and pistils styles and stigma. Induced by zeatin (PubMed:29258424). Induced by auxin (PubMed:29258424). Triggered by brassinosteroids (PubMed:29258424). Accumulates in reduced red/far-red light ration (R:FR) conditions mimicking shaded conditions (PubMed:29258424). Repressed by abscisic acid (PubMed:29258424). Belongs to the ARG7 family.