part_of part of part of protoxylem primary xylem tracheary element protoxylem tracheary element A primary xylem tracheary element (PO:0025444) with predominately annular or helical secondary wall thickening that are the first formed tracheary elements (PO:0000290) at a particular location. PO_GIT:440 In a given portion of primary xylem (PO:0005849), protoxylem tracheary elements are generally smaller in size, fewer in number, un-pitted and have less secondary wall material than metaxylem tracheary elements (PO:0025576). plant_anatomy elemento de traqueida del protoxilema (Spanish, exact) 2013-06-10T11:36:21Z PO:0025575 moorel 原生木部仮導管要素 (Japanese, exact)