cambium-like transitional zone If found, this zone is a temporary feature mostly in Gymnosperms. OBSOLETE. A cup-shaped region in the shoot apical meristem found between the central mother cell and the rib and peripheral zone. The cells of this zone are derived from the corpus intials, but in some cases they arise also from tunica initials. PO:0006067 adaxial meristem (related) leaf meristem (related) plant_anatomy true ventral meristem (related) zona transicional semejante al cambium (Spanish, exact) 形成層様移行帯 (Japanese, exact)