Transport in plants — Edexcel GCSE Combined Science
Root hair cells, xylem and phloem, transpiration and the stomata, and translocation of sucrose.
Revision notes
4 short notes, in the order of the specification. Each one in short:
Root hair cells take in water and mineral ions from the soil. The long, thin root hair gives a large surface area, and a thin cell wall gives a short distance to cross. Water enters by osmosis, while mineral ions such as nitrate ions are taken in by active transport, using energy released by many mitochondria.
Xylem and phloem are the two transport tissues in a plant. Xylem carries water and mineral ions from the roots and is made of lignified dead cells that form hollow tubes. Phloem carries sucrose and is made of living sieve tube cells and companion cells, whose mitochondria release the energy needed for transport.
Transpiration is the loss of water vapour from a plant, mainly through the stomata in the leaves. It pulls the transpiration stream of water and mineral ions up the xylem from the roots. Guard cells control the stomata: they swell and open the stoma when they take in water, and become limp and close it when they lose water.
Translocation is the transport of sucrose around the plant, dissolved in water in the phloem. Sucrose moves from the leaves, where it is made, to parts that use or store it, such as growing shoot tips, roots, flowers and fruits. It can move up or down, and needs energy released by respiration in the living phloem cells.
Exam questions
8 exam-style questions (24 marks), each with its mark scheme.
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15 cards: flip them, mark what you knew, and practise the rest.
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The whole of plant structures and their functions on one page, so you can see where this subtopic fits.
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Quick check questions
Give two adaptations of a root hair cell.
Show answer
Any two of: a long, thin projection for a large surface area; many mitochondria for active transport; a thin cell wall.
Why is xylem made of lignified dead cells?
Show answer
Dead cells with no end walls form a continuous hollow tube for water, and lignin strengthens the walls.
What is transpiration?
Show answer
The loss of water vapour from the leaves, which pulls water through the plant.
What is translocation?
Show answer
The transport of sucrose around the plant in the phloem.
Frequently asked questions
How are root hair cells adapted to their function?
Root hair cells are adapted to absorb water and mineral ions from the soil. The long, thin root hair gives a large surface area, and the thin cell wall gives a short distance to cross. Many mitochondria release energy for the active transport of mineral ions, and concentrated cell sap lets water enter by osmosis.
Why is active transport needed in plant roots?
Active transport is needed because mineral ions, such as nitrate ions, are usually at a lower concentration in the soil water than inside the root hair cell. They cannot move in by diffusion, so they are moved from a lower to a higher concentration by active transport, which uses energy released by respiration in the mitochondria.
How does water move from roots to leaves?
Water moves from roots to leaves in the transpiration stream. Water is absorbed from the soil by root hair cells and moves up through the xylem to the leaves. It evaporates from the cells inside the leaf into the air spaces and diffuses out through the stomata. This loss of water pulls more water up the xylem.
What is the difference between xylem and phloem?
Xylem carries water and mineral ions from the roots to the rest of the plant, while phloem carries sucrose around the plant. Xylem is made of dead cells with walls thickened with lignin, forming hollow tubes. Phloem is made of living sieve tube cells and companion cells, and needs energy for transport.
What is the difference between translocation and transpiration?
Translocation is the transport of sucrose in the phloem, and it needs energy from respiration in the living phloem cells. Transpiration is the loss of water vapour from the leaves, which moves water and mineral ions up the xylem. Transpiration does not use energy from the plant's cells, and xylem cells are dead.
Written and checked against the Edexcel GCSE Combined Science (1SC0) specification · Updated October 2026