Distinguish between the apoplast and the symplast pathways of water movement.

In the apoplast pathway water moves through the cell walls and intercellular spaces without crossing any membrane, so it moves quickly and passively. In the symplast pathway water moves from cell to cell through the cytoplasm and the plasmodesmata, which is slower. At the endodermis the Casparian strip blocks the apoplast route and forces water into the symplast.

No citable source has been recorded for this record. Treat it as practice material, not as fact.

Explanation

This is how the plant controls what enters the xylem.