Plant Water Transport Pathways: Apoplast vs. Symplast

Steps:

• Recall apoplast pathway: water flows through cell walls and intercellular spaces, bypassing cell membranes.
• Recall symplast pathway: water moves cell-to-cell via cytoplasm and plasmodesmata.
• Identify barriers: Casparian strip in endodermis blocks apoplast, forcing symplast entry to xylem.
• Evaluate options against definitions to find the accurate statement.

Why C is correct:

• The Casparian strip, a waxy band in root endodermis cell walls, waterproofs the apoplast pathway, preventing unregulated water and solute entry.

Why the others are wrong:

• A: Plasmodesmata connect cell cytoplasms, so they enable symplast, not apoplast transport.
• B: Intercellular spaces are part of the apoplast; symplast uses plasmodesmata, not spaces.
• D: Tonoplast is the vacuole membrane inside cells and does not block the symplast pathway between cells.

Final answer: C