Why are functional xylem water-conducting cells dead?

Functional xylem water-conducting cells, such as tracheids and vessel members, are dead at maturity because their protoplasts—the living contents of the cell—break down and dissolve after their cell walls have fully developed and been reinforced with lignin.123

This process is a form of "programmed death" that serves a critical biological function: by removing the living cytoplasm, the entire interior of the cell becomes an empty, hollow space. This structural adaptation allows for the rapid, unimpeded transport of water and dissolved minerals from the roots to the rest of the plant. Because these cells are reinforced by strong, woody walls, they remain structurally sound even after the living components are gone, effectively forming a rigid, hollow skeleton that provides both the necessary conduit for fluid transport and essential physical support for the plant.14352