Answer: Xylem.
- A Phloem
- B Xylem
- C Both xylem and phloem
- D Cell membrane only
Correct answer: B. Xylem
Explanation: Xylem transports water and minerals from roots to leaves (upward). Phloem transports sugars (both up and down).
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.