root cap formation stage root cap formation in crown root. (related) plant_structure_development_stage 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. PO:0007501 root cap formation in primary root. (related) root cap formation in lateral root. (related) The stage at which the root cap becomes evident. 3 establishment of tissue systems stage