Apoplast Pathway Transport Mechanisms

Steps:

• Identify the route: movement through cell walls without crossing membranes describes the apoplast pathway in plant roots.
• Recall definitions: diffusion is passive movement down a concentration gradient; osmosis is water diffusion across a semi-permeable membrane down a water potential gradient.
• Apply to water: in apoplast, no membrane is involved, but water follows osmotic gradients established by root cells, termed osmosis in standard biology contexts.
• Apply to ions: ions move passively down electrochemical gradients through porous cell walls via diffusion.

Why B is correct:

• Osmosis drives water movement toward higher solute concentrations in roots (definition: net water flow across membrane due to solute gradient), while ions diffuse independently through walls.

Why the others are wrong:

• A: Ions do not move by osmosis, as osmosis specifically involves water, not solutes.
• C: Identical to B, likely a duplicate option.
• D: Ions do not move by osmosis; requires membrane and applies only to water.

Final answer: B