Extracellular signaling peptide that may regulate primary root growth rate and systemic nitrogen (N)-demand signaling. Interacts with CEP receptors (e.g. CEPR1 and CEPR2). Accumulates in xylem sap. Slightly repressed in roots by carbon dioxide CO(2). Induced in shoots by osmotic stress (e.g. mannitol). The mature small signaling peptide is generated by proteolytic processing of the longer precursor. Belongs to the C-terminally encoded plant signaling peptide (CEP) family.