NEET · BiologyMedium
In the context of the pressure flow hypothesis for phloem transport, what is the primary driver of the movement of sucrose from source to sink?
- A.Active transport of water into the sieve tubes
- B.Hydrostatic pressure gradient generated by osmotic water uptake
- C.ATP-dependent movement of sucrose along the sieve plate
- D.Transpiration pull generated by the leaves
Show correct answer & step-by-step solution
Correct answer: B — Hydrostatic pressure gradient generated by osmotic water uptake
Solution
- Sucrose is actively loaded into the phloem at the source, lowering the water potential.
- Water enters the phloem from the xylem via osmosis, increasing the hydrostatic pressure.
- At the sink, sucrose is unloaded, increasing the water potential and causing water to exit.
- The resulting hydrostatic pressure gradient drives the bulk flow of sap. Hence the answer is (B).
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