AQA · GCSE · Biology
Course version: 8461 · Version from Sept 2018
Phloem tissue transports dissolved sugars from the leaves to the rest of…
Full specification wording
Plant organ system: Phloem tissue transports dissolved sugars from the leaves to the rest of the plant for immediate use or storage.
Carrot roots store mainly sucrose, so use potato tubers or seeds for starch storage examples.
Checked against the AQA 8461 specification (opens in a new tab) on .
- Point 11 of 13
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Carrot roots store mainly sucrose, so use potato tubers or seeds for starch storage examples. Phloem is the plant tissue that carries dissolved sugars, mainly sucrose, made in photosynthesis. Leaves are the source where sugar is loaded into phloem; growing regions, roots, fruits, and storage organs are sinks where sugar is unloaded. Transport in phloem is called translocation and occurs in different directions depending on need. Phloem tissue contains sieve tube elements joined end to end with perforated sieve plates, and companion cells that support the sieve tubes with energy. Sugars are used immediately for respiration and growth, or converted to starch and stored in organs such as potato tubers and seeds.
What earns the marks
- Carrot roots store mainly sucrose, so use potato tubers or seeds for starch storage examples.
- Phloem transports dissolved sugars, especially sucrose, around the plant.
- The leaves are the main source of sugars because photosynthesis occurs there.
- Translocation can occur in different directions, unlike the mainly one-way flow in xylem.
- Sieve tube elements form tubes with sieve plates, and companion cells support their function.
Common mistakes and how to put them right
Using carrot roots as an example of starch storage.
Put it right: Use potato tubers or seeds, as carrots store mainly sucrose.
Saying phloem carries water and mineral ions.
Put it right by stating that xylem carries water and ions while phloem carries dissolved sugars.
Claiming phloem transport is always downwards.
Put it right by explaining that translocation moves sugars from source to sink, which may be up or down.
Exam tips
- Use the terms source and sink to explain the direction of sugar movement in phloem.
- Name sucrose as the main transported sugar and give a named storage example such as starch in a potato tuber.
Try the lesson
The start of the Plant organ system: Phloem tissue transports dissolved sugars from the leaves to the rest of the plant for immediate use or storage. lesson, made from checked teaching notes for this specification point.
Have a go first
Which plant tissue carries dissolved sugars from the leaves to the rest of the plant?
Listen
Carrot roots store mainly sucrose, so use potato tubers or seeds for starch storage examples. Phloem is the plant tissue that carries dissolved sugars, mainly sucrose, made in photosynthesis. Leaves are the source where sugar is loaded into phloem; growing regions, roots, fruits, and storage organs are sinks where sugar is unloaded. Transport in phloem is called translocation and occurs in different directions depending on need. Phloem tissue contains sieve tube elements joined end to end with perforated sieve plates, and companion cells that support the sieve tubes with energy. Sugars are used immediately for respiration and growth, or converted to starch and stored in organs such as potato tubers and seeds. A strong answer earns marks for these points. Carrot roots store mainly sucrose, so use potato tubers or seeds for starch storage examples. Phloem transports dissolved sugars, especially sucrose, around the plant. The leaves are the main source of sugars because photosynthesis occurs there. Translocation can occur in different directions, unlike the mainly one-way flow in xylem. A common slip: Using carrot roots as an example of starch storage. Instead, use potato tubers or seeds, as carrots store mainly sucrose. Exam tip: Use the terms source and sink to explain the direction of sugar movement in phloem.
See it
Key words
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Translocation
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Source
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Sink
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Phloem
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See every definition
- Translocation
- Transport in phloem, which occurs in different directions depending on need.
- Source
- The leaves, where sugar is loaded into phloem because photosynthesis occurs there.
- Sink
- Growing regions, roots, fruits, and storage organs where sugar is unloaded.
- Phloem
- Plant tissue that transports dissolved sugars, especially sucrose, around the plant.
Label the diagram
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