Answer: Water potential.
- A Cell wall thickness
- B Water potential
- C Number of stomata
- D Chlorophyll content
Correct answer: B. Water potential
Explanation: Water always moves from higher to lower water potential, so the gradient between cells decides its direction.
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.