May be involved in cell polarity control during the actin-dependent tip growth of pollen tubes. Inactive GDP-bound Rho GTPases reside in the cytosol, are found in a complex with Rho GDP-dissociation inhibitors (Rho GDIs), and are released from the GDI protein in order to translocate to membranes upon activation. Interacts with SPK1. Associated with the membrane when activated. Ubiquitous. Preferentially expressed in mature pollen and pollen tubes. Belongs to the small GTPase superfamily. Rho family.