What does it mean to impregnate xylem a cell wall?

The walls of xylem cells are lignified (strengthened with a substance called lignin). This allows the xylem to withstand pressure changes as water moves through the plant.

Explanation:

The xylem transports water and minerals from the roots up the plant stem and into the leaves.

In a mature flowering plant or tree, most of the cells that make up the xylem are specialised cells called vessels.

Vessels:

from my research i have to the conclusion that decomposers, such as fungi, bacteria and invertebrates, play a critical role in nutrient cycling and without them the earth's ecosystem may not support life as we know it. elements such as carbon, nitrogen and phosphorus exist in limited amounts on earth, although huge amounts of carbon are being released into the atmosphere from underground sources now by humans. it is still extremely important that other nutrients be retained by the process of re-use. decomposers are organisms that are able to chemically break down dead material and make these elements available for use by other organisms. without this breakdown of dead material, dead bodies would pile up. so decomposers also play a role in clean up also. without them, life might not continue as we know it and dead material would overwhelm the earth.    

several tissues working together form an organ, and several organs together make up an organisms.

the group of cell that carries out special jobs are tissue.