- A Upward water movement in xylem driven by transpirational pull
- B Sugar transport in phloem (source to sink via turgor pressure gradient)
- C Root pressure generated by active ion accumulation in root xylem at night
- D Stomatal opening triggered by guard cell turgor changes at dawn
Correct answer: B. Sugar transport in phloem (source to sink via turgor pressure gradient)
Explanation: Pressure flow (Munch hypothesis): sugars loaded at source increase osmotic pressure, water enters by osmosis, creating pressure that pushes sap through phloem to sink.
Concept context
Water and mineral absorption, the ascent of sap, transpiration, and phloem transport via the pressure flow hypothesis.