Xylem and phloem — Cambridge IGCSE Biology
The functions of xylem and phloem, where they are in roots, stems and leaves, and how xylem vessels are adapted.
Revision notes
2 short notes, in the order of the specification. Each one in short:
Xylem and phloem are the two transport tissues in plants. Xylem transports water and mineral ions upwards from the roots and supports the plant, while phloem transports sucrose and amino acids. Xylem vessels have thick walls containing lignin, no cell contents, and cells joined end to end with no cross walls, forming a long continuous tube.
Xylem and phloem are found together in vascular bundles in the roots, stems and leaves of a dicotyledonous plant. In the root, xylem is in the centre, often in an X shape, with phloem between its arms. In the stem, bundles form a ring with xylem inside and phloem outside. In a leaf vein, xylem lies above phloem.
Exam questions
6 exam-style questions (15 marks), each with its mark scheme.
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7 cards: flip them, mark what you knew, and practise the rest.
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The whole of transport in plants on one page, so you can see where this subtopic fits.
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Quick check questions
What does phloem transport?
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Sucrose and amino acids.
What are the two functions of xylem?
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Transport of water and mineral ions, and support.
In a stem, which tissue is on the outside of a vascular bundle?
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Phloem.
Supplement Why do xylem vessels have no cross walls?
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The cells are joined end to end to make a long continuous tube.
Frequently asked questions
What is the difference between xylem and phloem?
Xylem transports water and mineral ions upwards from the roots and also supports the plant. Phloem transports sucrose and amino acids around the plant. Both are found together in vascular bundles. In a stem, phloem is on the outside of each bundle and xylem is on the inside.
How are xylem vessels adapted to their function?
Supplement Xylem vessels have thick walls containing lignin, which makes them strong so they do not collapse and the plant is supported. They have no cell contents, so nothing blocks the water. Their cells are joined end to end with no cross walls, forming a long continuous tube so water moves up in one unbroken column.
Where are xylem and phloem in a root?
In a root, the xylem and phloem are in the centre. The xylem is in the middle, often in an X or star shape, and the phloem lies between the arms of the X. This is different from the stem, where the vascular bundles form a ring near the outside of the stem.
Written and checked against the Cambridge IGCSE Biology (0610) specification · Updated October 2026