Phloem Transport
Hardbiology
Which process explains movement of photosynthates from source to sink in phloem?
Select the correct option:
Solution
Incorrect! Answer:
Pressure flow hypothesis
- Translocation: The transport of food (sucrose) in the phloem.
- Pressure Flow Hypothesis: Also known as the Mass Flow Hypothesis.
- Mechanism:
- Active loading of sucrose at the source (leaf) creates a high solute concentration, drawing in water and increasing hydrostatic pressure.
- At the sink (roots/fruits), sucrose is unloaded, water leaves the phloem, and pressure drops.
- Flow: Sap moves in bulk from the high-pressure source to the low-pressure sink.
- Others: Transpiration pull and cohesion-tension apply to xylem water transport, not phloem.
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About This Question
- Subject
- biology
- Chapter
- structural organisation in animals and plants
- Topic
- phloem transport
- Difficulty
- Hard
- Year
- 2025
Solution
Correct Answer:
Pressure flow hypothesis
- Translocation: The transport of food (sucrose) in the phloem.
- Pressure Flow Hypothesis: Also known as the Mass Flow Hypothesis.
- Mechanism:
- Active loading of sucrose at the source (leaf) creates a high solute concentration, drawing in water and increasing hydrostatic pressure.
- At the sink (roots/fruits), sucrose is unloaded, water leaves the phloem, and pressure drops.
- Flow: Sap moves in bulk from the high-pressure source to the low-pressure sink.
- Others: Transpiration pull and cohesion-tension apply to xylem water transport, not phloem.
This hard difficulty biology question is from the chapter structural organisation in animals and plants, covering the topic of phloem transport. It appeared in the 2025 exam.
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