Casparian Strip Function in Root Water Transport

Steps:

• Casparian strip forms in endodermal cell walls as a waterproof barrier.
• Composed mainly of suberin with some lignin, it impregnates the cell wall.
• Blocks apoplastic flow (through cell walls) of water and solutes.
• Forces movement through symplast (cell cytoplasm) for selective control.

Why B is correct:

• By definition, the Casparian strip is a suberin band in endodermal cell walls that seals the apoplastic pathway, regulating entry to the stele.

Why the others are wrong:

• A: Occurs in endodermal (not cortical) cells and blocks apoplast (not symplast).
• C: Located in cell walls (not cytoplasm) of endodermal (not cortical) cells.
• D: Blocks apoplast (not symplast) and is in cell walls (not cytoplasm).

Final answer: B