Answer: Symplast (through cell membrane), allowing selective mineral ion transport to xylem.
- A The apoplast pathway mainly, bypassing most endodermal cell membranes encountered along the way
- B Symplast (through cell membrane), allowing selective mineral ion transport to xylem
- C Suberized cell walls alone, with little membrane crossing required at any point along the path
- D Stomatal pores located within the endodermal cell layer of the root structure itself
Correct answer: B. Symplast (through cell membrane), allowing selective mineral ion transport to xylem
Explanation: Casparian strip: suberin band in endodermis cell walls blocks apoplast pathway. Water and solutes MUST cross the endodermal plasma membrane (symplast), allowing selective ion transport control.
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.