Answer: stomata.
- A stomata
- B xylem
- C phloem
- D root hairs
Correct answer: A. stomata
Explanation: Changes in guard-cell turgor open or close the stomatal pore.
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.