Sugars, amino acids and other organic substances (nutrients) are transported in phloem.
Translocation starts at a source, such as a leaf where sugars are made.
Sugars are transported into phloem by active transport across the membranes of the living phloem cells.
Water moves into the phloem cells by osmosis, which increases the pressure and pushes the sugars along the phloem tube.
Sugars are transported out of the phloem by active transport at a sink, such as a developing root, stem or flower.

Common misconception

Students get confused between transport in the xylem (water and minerals) and the phloem (sugars).

These sections are covered in separate lessons, each with clear explanations and reinforcing tasks to support learning.

Keywords

Phloem - specialised vessels in plants that transport sugar, amino acids and other nutrients
Translocation - the process of transporting sugars and nutrients through the phloem
Source - the location that the sugars or nutrients are loaded during translocation
Sink - the location that the sugars or nutrients are unloaded during translocation
Active transport - the net movement of particles against a concentration gradient using energy

Bring in a sample of sources, sinks and sap, including leaves, roots, potatoes, flowers, seeds and maple syrup, to give students a real-world view of why translocation is needed.

Teacher tip

Equipment

None required.

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Video

Skip video

Worksheet

Download worksheet

Skip worksheet

Starter quiz

Download starter quiz

6 Questions

Q1.

Which part of the plant pictured - A, B, C or D - absorbs water for photosynthesis?

Correct Answer: D, d

Q2.

Which part of the plant is adapted to make a lot of glucose by photosynthesis?

Correct Answer: leaf, leaves, palisade mesophyll, palisade mesophyll cells, palisade mesophyll cell

Q3.

Name the vessels that transport water from the roots to the leaves in plants.

phloem

veins

Correct answer: xylem

capillaries

arteries

Q4.

What may happen to a non-woody plant if the rate of uptake of water by the roots is less than the rate of transpiration?

the plant will photosynthesise faster

the plant will grow faster

the plant will stop photosynthesising

Correct answer: the plant will wilt

Q5.

When it is dark at night, plants close their stomata. How will this affect life processes in the plant?

It will increase the rate of cellular respiration.

It will decrease the rate of photosynthesis.

It will increase the rate of transpiration.

Correct answer: It will decrease the rate of transpiration.

Q6.

Which statement explains why the majority of stomata are on the underside of leaves?

water is lost through stomata

Correct answer: the top surface of a leaf is warmer than the lower

the waxy cuticle is on the lower surface

there are more air spaces on the upper surface

Exit quiz

Download exit quiz

6 Questions

Q1.

Some of the __________ produced by photosynthesis is used in cellular respiration to transfer energy for life processes.

Correct answer: glucose

carbon dioxide

water

light

chlorophyll

Q2.

Which of these statements is correct?

All plant cells can photosynthesise.

All root cells can photosynthesise.

All cells can photosynthesise.

Correct answer: All cells with chloroplasts can photosynthesise.

Q3.

Match each keyword to the correct meaning.

Correct Answer:transpiration ,the loss of water from a plant's leaves

the loss of water from a plant's leaves

Correct Answer:translocation ,the transport of sugars and other nutrients in plants

the transport of sugars and other nutrients in plants

Correct Answer:xylem ,specialised tissue for the transport of water and minerals

specialised tissue for the transport of water and minerals

Correct Answer:phloem ,specialised tissue for the transport of sucrose and amino acids

specialised tissue for the transport of sucrose and amino acids

Q4.

Cells in plant leaves are like factories for the production of biological molecules. Match each biological molecule to the components from which it is made.

Correct Answer:amino acids ,glucose and nitrate ions

glucose and nitrate ions

Correct Answer:starch,thousands of glucose molecules joined together

thousands of glucose molecules joined together

Correct Answer:chlorophyll ,glucose and magnesium

glucose and magnesium

Q5.

Which of these is not true of phloem tissue?

phloem tissue is alive

phloem tissue cells have cytoplasm

phloem cells have sieve plates between them

Correct answer: phloem tissue transports only from the leaves to the roots

Q6.

Put these stages of translocation in the correct order.

1 - Active transport moves sugars from the source into the phloem.

2 - This increases the concentration of sugar in the phloem.

3 - Osmosis moves water into the phloem.

4 - The water increases the pressure in the phloem.

5 - Sugar solution moves towards the sink by translocation.