Promotes plant cell differentiation, organogenesis and somatic embryogenesis as well as cell proliferation. Expressed in roots, mature leaves, stems, flowers and siliques. Most abundant in vascular bundles. Up-regulated by wounding. Sulfation is important for activity and for the binding to a putative membrane receptor. PSK-beta is an enzymatic derivative of PSK-alpha. Belongs to the phytosulfokine family. Truncated N-terminus.