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IGCSE · Practice questions · Xylem and phloem

Water up, food around.

Six original Cambridge-style questions on what xylem and phloem carry, where they sit in roots, stems and leaves, and (Extended) why lignified, hollow, end-to-end xylem vessels make good water pipes.

Original questions All questions on this page are original work, written in the Cambridge IGCSE style. They are not from past papers. They test the same concepts and skills the syllabus rewards.
Keep these straight

Two tissues, three organs.

01
Recall
[3 marks]

State the functions of xylem and of phloem.

  • Xylem transports water and mineral ions (from the roots to the rest of the plant). ✓
  • Xylem also helps to support the plant. ✓
  • Phloem transports sucrose and amino acids. ✓
02
Analysis
[3 marks]

A student is shown three transverse sections from a bean plant. Section P has a star-shaped central tissue. Section Q has separate bundles of tissue in a ring. Section R is thin and flat with a thick central region. Identify the organ each section came from and state where the xylem is in each.

  • P is a root: the xylem is the star (cross) shape in the centre. ✓
  • Q is a stem: the xylem is in each vascular bundle, on the side towards the centre. ✓
  • R is a leaf: the xylem is in the veins / midrib, on the upper side, with the phloem below. ✓
03
Explain
[3 marks]

Extended. Explain how three features of xylem vessels make them suited to their function.

  • Thick walls with lignin: strong, so the vessels do not collapse and they support the plant. ✓
  • No cell contents: no cytoplasm or organelles to block the flow of water. ✓
  • Cells joined end to end with no cross walls: form a long continuous tube, so water and mineral ions flow from root to leaf without interruption. ✓
04
Explain
[2 marks]

The phloem in the stem of a plant is damaged by an insect. Suggest and explain one effect on the roots.

  • Less sucrose (and fewer amino acids) reaches the roots through the phloem. ✓
  • So the root cells have less sucrose for respiration and growth (and less is stored), so root growth slows. ✓
05
Recall
[2 marks]

A ringed (bark-removed) branch still has green leaves a week later, but swelling appears just above the ring. Removing the bark removes the phloem but leaves the xylem. Explain why the leaves stay green.

  • The xylem is still intact, so water and mineral ions still reach the leaves. ✓
  • So the leaf cells stay supplied with water and remain alive (the swelling above the ring is where sucrose in the phloem builds up because it cannot pass). ✓
06
Analysis
[3 marks]

Extended. Compare the structure of a xylem vessel with a phloem sieve tube. Give three differences.

  • Xylem vessels are dead; sieve tubes are living cells. ✓
  • Xylem vessels have no cell contents; sieve tubes contain cytoplasm. ✓
  • Xylem has no cross walls; sieve tubes have sieve plates (perforated cross walls). Also accept: xylem walls are lignified, phloem walls are not. ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.