alleryThe main DRIVING FORCE for upward water + mineral transport in tall trees is:
ARoot pressure (only at dawn typically)
BCapillary action (within thin xylem)
CActive pumping by the leaf cells
DTranspiration pull (cohesion-tension theory)
Answer & Solution
Correct answer: D. Transpiration pull (cohesion-tension theory)
**TRANSPIRATION PULL drives sap up:** water evaporates from leaves
→ tension pulls more water up through xylem (cohesion of water molecules + adhesion to xylem walls).
Dixon-Joly cohesion-tension theory.
Root pressure plays a minor role.
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