Answer: pathway.
- A pathway
- B colour
- C temperature
- D only the speed
Correct answer: A. pathway
Explanation: The waterproof Casparian strip forces water and ions through the cell membranes, regulating their pathway.
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.