Translocation — Cambridge IGCSE Biology
Movement of sucrose and amino acids in the phloem from sources to sinks.
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Translocation is the movement of sucrose and amino acids in the phloem from sources to sinks. A source is a part of the plant that releases sucrose or amino acids, such as a mature green leaf. A sink uses or stores them, such as a growing root tip or developing seed. A potato tuber can be both at different times.
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Quick check questions
Supplement Define translocation.
Show answer
The movement of sucrose and amino acids in the phloem from sources to sinks.
Supplement What is a sink?
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A part of the plant that uses or stores sucrose or amino acids.
Supplement Give an example of a source.
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A fully grown green leaf.
Supplement Why can a tuber be both?
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It stores sucrose (as starch) as a sink, then releases sucrose as a source when new shoots grow.
Frequently asked questions
What is translocation in plants?
Translocation is the movement of sucrose and amino acids in the phloem from sources to sinks. A source, such as a mature green leaf in the light, releases sucrose made in photosynthesis. A sink, such as a growing shoot tip or a developing fruit, uses or stores the sucrose it receives.
What is the difference between a source and a sink in a plant?
A source is a part of the plant that releases sucrose or amino acids, such as a mature green leaf. A sink is a part of the plant that uses or stores sucrose or amino acids, such as a root tip, a developing seed or a potato tuber. Sucrose always moves from source to sink.
How can a potato tuber be both a source and a sink?
A potato tuber is a sink while the plant is growing and photosynthesising, because it receives sucrose and stores it as starch. When the tuber starts to grow new shoots, the starch is broken down and sucrose is released and moved to the shoots, so the same organ becomes a source.
Written and checked against the Cambridge IGCSE Biology (0610) specification · Updated October 2026