root cap formation stage PO:0007501 The number and origin of root cap initials that form the root cap varies among species. The root cap initials become independent from the more internally located root meristem cells by an increase in the thickness of the cell wall that separates them. The stage at which the root cap becomes evident. plant_structure_development_stage root cap formation in crown root. (related) root cap formation in lateral root. (related) root cap formation in primary root. (related) 3 establishment of tissue systems stage