root epidermal differentiation stage Root hairs come to full development beyond the region of elongation zone, approximately at the level where the xylem begins to mature. epidermial differentiation of crown root. (related) PO:0007516 epidermal differentiation of primary root (related) plant_structure_development_stage The stage at which the root epidermis becomes evident. epidermal differentiation of lateral root. (related) 3 establishment of tissue systems stage