Answer: phloem.
- A phloem
- B xylem
- C epidermis
- D cortex
Correct answer: A. phloem
Explanation: The pressure-flow hypothesis describes how sugars move in the phloem.
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.