Acts as a GTPase activator for the Rac-type GTPase by converting it to an inactive GDP-bound state. Maintains the global inactivation of ARAC11/ROP1 at the apex in pollen tubes in order to regulate the polar cell growth. Interacts with ARAC11/ROP1. Localizes to the apical plasma membrane and accumulates in the clear zone of growing pollen tubes. Expressed in pollen and pollen tubes. Male gametophyte defect characterized by sterile pollen grains developing balloon-like tubes.