Apoplast Pathway Relies on Cell Walls and Spaces

Steps:

• Recall that the apoplast pathway involves water movement through non-living parts of the plant, like cell walls and intercellular spaces.
• Distinguish apoplast from symplast: apoplast avoids crossing cell membranes, unlike symplast via cytoplasm.
• Identify key routes: water flows freely in cell walls and gaps between cells without entering protoplasts.
• Eliminate options requiring membrane crossing or specific barriers.

Why B is correct:

• The apoplast pathway is defined as water transport through the continuum of cell walls and intercellular spaces, allowing passive diffusion without cellular entry.

Why the others are wrong:

• A: Adjacent cell surface membranes are crossed in the symplast pathway, not apoplast.
• C: Plasmodesmata connect living cytoplasms in the symplast pathway.
• D: The Casparian strip blocks apoplast flow in roots, forcing symplast entry.

Final answer: B