8.4 Translocation
Movement of Sucrose & Amino Acids in Phloem
EXAMINER TIP:
Translocation is NOT just "downward" - it goes from SOURCE → SINK, which can be UP or DOWN depending on the season!
What is Translocation?
Definition:
The movement of Sucrose and Amino Acids through the Phloem from a Source to a Sink.
SOURCE
The part of the plant that RELEASES or PRODUCES sucrose.
Examples:
- Summer: Mature leaves (photosynthesizing)
- Spring: Storage organs (tubers releasing stored food)
SINK
The part of the plant that USES or STORES sucrose.
Examples:
- Summer: Roots, fruits, tubers (storing food)
- Spring: Growing buds, new leaves (using food for growth)
🔑 KEY PRINCIPLE:
Direction of translocation changes with seasons because sources and sinks swap roles!
Core vs Supplement Content:
Understand that translocation moves sucrose and amino acids from sources to sinks
Explain how sources and sinks change with seasons (e.g., potato plant in summer vs spring)
📝 Exam Essentials:
✓ Translocation = Movement of SUCROSE and AMINO ACIDS in PHLOEM
✓ Direction is SOURCE → SINK (not always downward!)
✓ Sources and sinks swap roles depending on the season
✓ Use precise terminology: "sucrose" not "sugar", "phloem" not "tubes"
✓ Starch is converted to sucrose for transport because starch is insoluble
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