- A Root pressure from active ion accumulation in roots according to standard texts
- B Active pumping of water by living xylem parenchyma cells under typical physiological conditions
- C Evaporation from mesophyll cells creating tension that pulls water up
- D Osmotic flow of water moving from phloem into xylem in general clinical practice
Correct answer: C. Evaporation from mesophyll cells creating tension that pulls water up
Explanation: As water evaporates from leaf mesophyll cells during transpiration, it creates a negative pressure (tension) that is transmitted down the continuous water column in the xylem, pulling water upward from the roots.
Concept context
Water and mineral absorption, the ascent of sap, transpiration, and phloem transport via the pressure flow hypothesis.