Xylem carries water and minerals upwards and supports the plant. Phloem carries sugar in both directions. Each structural feature matches one of these jobs.
This lesson belongs to transport in plants. It is the summary lesson, so it helps to have read explaining translocation first.
How do the two tissues compare?
Compare on the same row each time: substance, direction, cell type, walls and living status.
| Feature | Xylem | Phloem |
|---|---|---|
| Substance carried | Water and mineral ions | Sucrose and other organic substances |
| Direction | Upwards only | Up and down |
| Cells | Vessels, fibres | Sieve tubes, companion cells |
| Cell contents | Dead, hollow | Living |
| Walls | Thick, with lignin | Thin cellulose |
| Extra job | Supports the plant | None |
Why does each feature exist?
Every feature has a reason. Give it, and the comparison becomes an explanation.
- Xylem is hollow and dead so water flows without obstruction.
- Lignin strengthens the wall so the vessel does not collapse under the pull.
- Sieve tubes are living and have companion cells, because moving sugar needs energy.
Worked example: a three-mark comparison
Question: compare xylem and phloem. (3 marks)
- Xylem carries water and minerals, while phloem carries sucrose.
- Xylem moves substances upwards only, while phloem moves them up and down.
- Xylem cells are dead and hollow with lignin, while phloem cells are living.
Each sentence has both tissues. That is how a comparison earns a mark: one idea, both sides, a clear contrast.
The mistake that loses marks
The weak answer lists each tissue in a separate paragraph. A comparison scores when each point sets the two tissues side by side.
| Weak | Strong |
|---|---|
| Xylem carries water. Phloem carries sugar. | Xylem carries water whereas phloem carries sucrose |
| Phloem is alive | Phloem is living because translocation needs energy |
| Xylem has lignin | Xylem has lignin to strengthen vessels against the pull |
Check yourself
A dye solution is given to a cut stem. The dye appears in the xylem but not in the phloem. Explain what this shows.
Answer
The dye moved with water, so it travelled in the xylem. The xylem carries water upwards by transpiration pull. The phloem carries sugar, not water, so the dye does not appear there.
What to study next
Test both tissues on the transport in plants practice set. Log any slips in the mistake log and paper-error review.
For a teacher who checks your comparison sentences as you write, see online one-to-one Biology tuition.