Promotes differentiation and/or maintenance of the vascular procambium, the initial cells of the developing vasculature (PubMed:20044450). Part of the TDIF-TDR-WOX4 signaling pathway that plays a crucial role in the maintenance of the vascular meristem organization during secondary growth (PubMed:20729381). Is required for promoting the proliferation of procambial/cambial stem cells but not for repressing their commitment to xylem differentiation in response to the TDIF signal (PubMed:20729381). Acts redundantly with WOX14 downstream of the TDR/PXY receptor kinase to regulate procambial cell proliferation and differentiation in vascular tissue, independently of any role in vascular (PubMed:23578929). Acts as a cambium regulator in the inflorescence stem (PubMed:21926336). Is required for auxin-dependent cambium stimulation in the inflorescence stem (PubMed:21926336). Expressed in the vasculature of the whole plant (roots, hypocotyls, cotyledons and leaves), trichomes and stomata (PubMed:20729381). Expresse in the developing vascular bundles of root and shoot lateral organs (PubMed:20044450). No visible phenotype under normal growth conditions (PubMed:20729381). The double mutants wox4 and wox14 exhibit reductions in vascular cell division (PubMed:23578929). Belongs to the WUS homeobox family.