Probable GTP-binding protein involved in cell wall expansion. Required for appropriate root and root hair cells enlargement. May inhibit vacuole enlargement during root hair cell expansion. Plays a role in cell wall biosynthesis and actin organization. Seems to act independently from auxin and ethylene pathways. May regulate membrane traffic from the Golgi apparatus towards the endoplasmic reticulum (ER). Highly expressed in fiber and xylem cells. Expressed in roots, cotyledons, seedling hypocotyls, stems, pedicel, stigmatic papillae cells and anthers. Expressed in the embryo throughout development. Reduced root and root hair length due to defect in epidermal cell growth and enlargement. Reduced size of vacuole and increase in the proportion of cytoplasm in root hair cells. Strong reduction in the cell wall thickness of fibers, vessels and pith cells in the inflorescence stems. Reduced cellulose content and altered composition of the cell wall. Altered organization of the actin cytoskeleton. Belongs to the TRAFAC class dynamin-like GTPase superfamily. GB1/RHD3 GTPase family. RHD3 subfamily.