The xylem is made from the xylem is made from elongated living cells intercellular spaces between cells tubular living cells dead, hollow cells

The xylem is made from dead, hollow cells.

Tracheids and vessel elements are the main components of xylem witch have a function to transport water. Those are elongated dead cells at maturity (without protoplast) with a thick, strengthened cellulose cell wall and a hollow lumen. Even though they are dead they still maintain a function, because are being protected by surrounding living cells.

The answer is ozone layer.