6.3Transport in Plants

Transport in Plants — Cambridge IGCSE Biology 0610 Revision Notes & Topical Questions

5 min read 12 parts Lesson 3 of 9 Unit quiz

📚 Cambridge IGCSE Biology 0610 Hub / Topical Revision

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Lesson summary

6.3 Transport in Plants — IGCSE BIOLOGY notes: Describe xylem and phloem, water uptake, transpiration and translocation in plants.Xylem — Vessels that transport water and minerals from the roots to the stem and leaves.Phloem — Vessels that transport sucrose and amino acids from p…

Vascular bundles
Position in a section
No cross walls
No contents
Root hairs
Surface area

Part 1 of 10Xylem and phloem

Xylem

Vessels that transport water and minerals from the roots to the stem and leaves.

Phloem

Vessels that transport sucrose and amino acids from photosynthesising leaves to non-photosynthesising regions in roots and stem.

Vascular bundles

Xylem and phloem are arranged in groups throughout the root, stem and leaves.

Position in a section

Xylem is always on the inside and phloem on the outside.

Part 2 of 10Xylem vessels (Supplement)

Xylem vessels (Supplement)

Function

Transport tissue for water and dissolved mineral ions, which also supports the plant.

No cross walls

Cells are joined end to end with no cross walls to form a long continuous tube.

No contents

Cells are essentially dead, with no cell contents, so water passes freely.

Lignin

The walls are thickened with lignin, which strengthens the tubes and helps support the plant.

Part 3 of 10Root hair cells and water uptake

Root hairs

Single-celled extensions of root epidermis cells that grow between soil particles.

Osmosis

Water enters because soil water has a higher water potential than the cytoplasm of the root hair cell.

Surface area

The large surface area increases the rate of absorption of water by osmosis and mineral ions by active transport.

Part 4 of 10Pathway of water

1Route

Root hair cell, root cortex cells, xylem, then leaf mesophyll cells.

2Movement across the root

Water moves across the cortex into the xylem by osmosis.

3Tracing it

Stand a celery stem in stained water for a few hours until the leaves take on the colour.
Cut a cross-section of the stem; the dye marks the xylem vessels.

Part 5 of 10Transpiration

Transpiration

Transpiration the loss of water vapour from plant leaves by evaporation at the surfaces of mesophyll cells followed by diffusion through the stomata.

Direction

Water moves in the xylem in one direction only, from roots to leaves.

Functions

It transports mineral ions, keeps cells turgid for support, supplies water for photosynthesis and cools the leaves.

Cooling

Heat energy is used to turn liquid water into vapour, which cools the plant.

Part 6 of 10Transpiration stream (Supplement)

Large surface area

Interconnecting air spaces between spongy mesophyll cells and the stomata give a large surface for rapid evaporation.

Cohesion

Water molecules attract each other and form a continuous column up the plant.

Pull

Transpiration creates a tension on the water in the xylem vessels, pulling the column up.

Faster transpiration

Water is pulled up the xylem faster.

Part 7 of 10Investigating temperature and wind speed

Dry the leaves of a shoot, because wet leaves affect the results.

Cut the shoot under water to prevent air entering the xylem and place it in the tube.

Make the apparatus airtight, using Vaseline to seal gaps.

Allow a single air bubble to form in the capillary tube.

Set up the factor under investigation and allow 5 minutes to acclimatise.

Record the starting position of the bubble and leave for a set time.

Record the end position of the bubble; a longer distance means a faster uptake.

Change only one factor, such as room temperature or fan speed, then reset the bubble and repeat.

Part 8 of 10Effects of temperature, wind speed and humidity (Supplement)

Factor	Condition	Effect on transpiration	Explanation
Wind speed	High	More	Moving air removes water vapour, keeping a steep concentration gradient out of the stomata
Humidity	High	Less	Air already contains much water vapour, so the gradient is smaller
Temperature	High	More	Greater kinetic energy raises evaporation and diffusion

Part 9 of 10Wilting (Supplement)

Cause

More water evaporates from the leaves than the roots can take up by osmosis.

Effect

Cells are not full of water, so cell walls cannot support the plant and it collapses.

Part 10 of 10Translocation and comparison

Translocation and comparison

Translocation

The movement of sucrose and amino acids in phloem from regions of production to regions of storage or use.

Source

A part that releases sucrose or amino acids; a sink uses or stores them.

Changing roles

In spring storage organs are sources and growing areas are sinks;
- in summer leaves are sources and roots are sinks.

Phloem structure

Living cells joined end to end with sieve plates that allow easy flow.

Tissue	Moves	Process	Direction	Cells
Xylem	Water and mineral ions	Transpiration stream	One way, roots to leaves	Dead
Phloem	Sucrose and amino acids	Translocation	In all directions	Living

Key terms

Term	Meaning
Xylem	Tissue of dead lignified vessels carrying water and mineral ions upwards.
Phloem	Tissue of living cells carrying sucrose and amino acids.
Transpiration	Loss of water vapour from leaves by evaporation and diffusion through stomata.
Translocation	Movement of sucrose and amino acids in the phloem from sources to sinks.
Source	A part of a plant that releases sucrose or amino acids.
Sink	A part of a plant that uses or stores sucrose or amino acids.
Cohesion	Attraction between water molecules.
Lignin	Substance thickening xylem walls.

Avoid these mistakes

Saying xylem carries food — xylem carries water and mineral ions; phloem carries sucrose and amino acids.

Saying water enters root hairs by active transport — water enters by osmosis and mineral ions by active transport.

Saying a potometer measures water loss directly — it measures water uptake, used as an estimate of transpiration.

Mixing up the positions in a section — xylem is on the inside and phloem on the outside.

Last updated: 12 October 2026