Final answer:
The water-conducting cells of xylem that have thick walls and are dead at functional maturity are tracheids and vessel elements.
Step-by-step explanation:
The water-conducting cells of xylem that have thick walls and are dead at functional maturity are tracheids and vessel elements.
Tracheids are xylem cells with thick secondary cell walls that are lignified. Water moves from one tracheid to another through pits on the side walls.
Vessel elements are shorter and have thinner walls compared to tracheids, and they are connected to each other through perforation plates.