Answer: transpiration pull.
- A transpiration pull
- B root pressure alone
- C capillary action alone
- D downward gravity
Correct answer: A. transpiration pull
Explanation: Transpiration pull, aided by water cohesion, mainly lifts sap in tall trees.
Water can travel through cell walls (apoplast) or cell-to-cell through the cytoplasm (symplast) - but the Casparian strip at the endodermis blocks the apoplast route entirely, forcing everything through a selectively permeable membrane (symplast) before it can enter the xylem.
Concept context
Water and mineral absorption, the ascent of sap, transpiration, and phloem transport via the pressure flow hypothesis.