Apoplast Pathway Relies on Cell Wall Components

Steps:

• Define apoplast pathway: water moves through cell walls and intercellular spaces from soil to xylem.
• Identify key structure: cell walls form continuous porous network for water flow.
• Link to plant components: cellulose comprises primary cell wall matrix allowing diffusion.
• Eliminate barriers: apoplast stops at endodermis, but cellulose enables initial movement.

Why B is correct:

• Cellulose forms the hydrophilic matrix of plant cell walls, permitting water to flow freely via the apoplast without entering cells.

Why the others are wrong:

• A. Casparian strip: suberized band blocking apoplast flow in endodermis.
• C. Endodermis: tissue layer containing Casparian strip that redirects water to symplast.
• D. Suberin: hydrophobic substance impregnating Casparian strip to prevent apoplast passage.

Final answer: B