Answer: Positive.
- A Positive
- B Always zero
- C Negative
- D Undefined
Correct answer: A. Positive
Explanation: As water fills a cell the wall pushes back, so the pressure potential becomes positive at full turgor.
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.