Modulates cell morphogenesis by regulating cell wall formation and assembly, and/or growth polarization. Together with LRX2, component of the extracellular mechanism regulating root hair morphogenesis and elongation. Specifically localized in the wall of the root hair proper. Expressed in root hair cells (at protein level). First observed in differentiating trichoblast and later confined to root hair proper. Soluble in the early stages of root hair development and becomes insolubilized in later stages. Hydroxylated on proline residues in the S-P-P-P-P repeat. O-glycosylated on hydroxyprolines. Irregular root hair development that frequently abort, swell, or branch. Stronger phenotype when associated with LRX2 disruption; frequent rupture of root hairs soon after their initiation.