Promotes plant cell differentiation, organogenesis and somatic embryogenesis as well as cell proliferation. Sulfation is important for activity and for the binding to a putative membrane receptor. Belongs to the phytosulfokine family. This potential protein codes for a PSK precursor that would produce a PSK-alpha that differs in the last residue (His) from a normal PSK-alpha (Gln). Furthermore there are no ESTs or cDNAs so far for this potential gene.