These vessel elements make up the xylem-and are many elongated cells laid end to end, and normal plant cells have walls strengthened by lignin, a hard strong substance that is impermeable to water, and is designed to provide structure and strength to the plant.rom the root hair cells, water again moves down a concentration gradient toward the xylem, and can take one of three paths-apoplast and symplast and vacuolar. The apoplast pathway is where water takes a route going from cell wall to cell wall, not entering the cytoplasm at any point.