Extracellular signal peptide that regulates cell fate. Represses root apical meristem maintenance. Mostly expressed in heart-shape embryos, pollen and young flower buds, and, to a lower extent, in inflorescence, leaves and roots. The O-glycosylation (arabinosylation) of the hydroxyproline Pro-68 enhances binding affinity of the CLE19p peptide for its receptor. Belongs to the CLV3/ESR signal peptide family.