Answer: transpiration.
- A transpiration
- B strong gravity
- C cell respiration
- D food digestion
Correct answer: A. transpiration
Explanation: Transpiration from the leaves creates a pull that draws water up the xylem.
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.