Question

Why can xylem transport water and minerals using dead cells whereas phloem requires living cells?

Answer 1

Xylem:

1. Xylem is the vascular tissue in plants, responsible for the conduction of water and mineral salts.
2. Additionally, the xylem provides mechanical strength.
3. It is composed of tracheids, xylem fibers, vessels, and xylem parenchyma.
4. Tracheids and vessels are the main water-conducting components of the xylem.
5. They are dead cells as they do contain any protoplasm.
6. They are elongated tube-like structures having a lignified wall.
7. The transport of water and minerals through the xylem occurs by the transpiration pull, i.e. the negative pressure which is generated due to the evaporation of water through leaves.

Phloem:

1. Phloem is also a vascular tissue in plants.
2. It transports food substances from leaves to growing parts.
3. It is composed of sieve tube elements, phloem parenchyma, companion cells, and phloem fibers in angiosperms.
4. It is composed of albuminous cells and sieve cells in gymnosperms.
5. Transport of food through the sieve tube elements of phloem require active transport.
6. This requires the expenditure of energy which can only be done by living cells.