A portion of meristem tissue (PO:0009013) that is committed to the development of a root primordium (PO:0005029). [source: POC:curators]
Comment
Only detectable by gene expression, not morphology. May arise in a pericycle (PO:0006203), as for lateral roots in most seed plants, an endodermis (PO:0000252), as for lateral roots in ferns, or from parenchyma cells (PO:0000074) that are part a shoot axis (PO:0025029), in the case of a basal root (PO:0025002) or shoot-borne root (PO:0000042).