root development stage At present the stages are described for primary, lateral and crown roots and stages for adventitious root formed by wounding or hormone treatment is not described. Finer resolution of root stages has been kept in the obsolete node as they are not consistently used in the consulted literature. These terms will be reintroduced into the ontology when there is a specific user request. PO:0007011 PO:0007520 Stages of development of a root defined by characteristic morphological, structural, histological or other visible features. plant_structure_development_stage root development stage (related) plant organ development stage