Answer: Pressure potential.
- A Osmotic gradient
- B Pressure potential
- C Matric tension
- D Kinetic energy
Correct answer: B. Pressure potential
Explanation: Water potential (Psi) = solute potential (Psi_s) + pressure potential (Psi_p).
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.