Plant Ontology National Agricultural Library Thesaurus Source
http://purl.obolibrary.org/obo/PO_0009065 http://lod.nal.usda.gov/nalt/210684 LOOM
http://purl.obolibrary.org/obo/PO_0020061 http://lod.nal.usda.gov/nalt/28072 LOOM
http://purl.obolibrary.org/obo/PO_0009053 http://lod.nal.usda.gov/nalt/57197 LOOM
http://purl.obolibrary.org/obo/PO_0025388 http://lod.nal.usda.gov/nalt/853 LOOM