In nonwoody plants the primary xylem is the only water-conducting tissue, but in mature plants with secondary growth this function is mostly taken over by the secondary xylem. 在尚未木质化的植物中，初生木质部是唯一的输水组织，但在具有次生生长的成熟植物中，该功能大多由次生木质部行使。
In nonwoody plants the primary xylem is the only water-conducting tissue, but in mature plants with secondary growth this function is mostly taken over by the secondary xylem. 在尚未木质化的植物中，初生木质部是唯一的输水组织，但在具有次生生长的成熟植物中，该功能大多由次生木质部行使。
