xylem element造句

• Protoxylem the primary xylem elements that are formed from the procambium first
  原生木质部：初生木质部的成分，最早由原形成层形成。
• Lumen the central space that remains , surrounded by cell walls , in a cell that has lost its living contents ( e . g . in xylem elements )
  胞腔：由细胞壁围成的空腔，其中的活性物质消失（如木质部中的管状分子） 。