Lesson 12 of 12 / Nutrition and transport in flowering plants
Translocation: moving sugars in plants
How can sugars travel down to roots and up to growing shoots?
I can define translocation as food transport, mainly sucrose, through phloem.
I can define translocation as food transport, mainly sucrose, in phloem.Syllabus
Syllabus K224 / K225, Topic 8(l). Define translocation as food transport, mainly sucrose, in phloem.
About 4 min
Make a guess. You are not marked.
A leaf makes sugar. A fruit growing above that leaf needs it. Can sugar move upwards in a plant?
Show the answer
Yes. Phloem carries it from source to sink.
Sugar moves from where it is made to where it is used or stored, upwards or downwards.
The key idea
Translocation moves food, mainly sucrose, through phloem from sources to sinks. Its direction depends on where food is supplied and used or stored.
Explore the idea
Where can the leaf send sucrose?
Translocation carries food, mainly sucrose, in phloem. The growing root receives food for respiration and growth even though it does not photosynthesise. Food does not always move downwards.
The highlighted arrow follows one food route. Other phloem pathways can supply other destinations at the same time.
Explanation
Translocation is the transport of food, mainly sucrose, in the phloem. Leaves that are photosynthesising make the sugar. Growing parts and storage organs need it.
Food can move up to growing shoots or down to the roots. It goes from where it is made to where it is needed, so it does not always move downwards.
Do not mix up translocation and transpiration. Translocation moves food in the phloem. Transpiration is the loss of water vapour from the leaves. Xylem carries water and mineral ions; phloem carries food.
Roots do not photosynthesise, but they still need sugar for respiration and growth. They get it from the leaves through the phloem.
Step by step
- 1
Name the cargo
Food, mainly sucrose.
- 2
Name the tissue
Phloem carries this food.
- 3
Name a destination
For example, a growing root, shoot or storage organ.
Worked example
Feeding a non-green root
How can a growing root obtain food made in a leaf? Name the process, main sugar and tissue.
One way to explain it
Sucrose is transported from the leaf to the growing root by translocation in phloem.
Why this answer works
- The root needs organic food for respiration and growth.
- Sucrose is the main transported food named here.
- Distinguish the phloem route from water flow in xylem.
Watch out for this
A student says: "Translocation means water evaporating from a leaf." What is wrong with this?
Show the answer
That is part of transpiration. Translocation is the movement of food, mainly sucrose, through phloem.
Check your understanding
Which correctly defines translocation?
Show the answer
Transport of food, mainly sucrose, in phloem.
Include both the transported material and the tissue.
Quick recall
How can sugars travel down to roots and up to growing shoots?