One type of plant cell that has holes in it to allow substances to flow through is a sieve tube element, found in the phloem tissue. These cells have sieve plates with holes that facilitate the flow of sugars, amino acids, and other substances up and down the plant. Another example is xylem vessel members, which have perforations (holes) in their cell walls allowing water to move relatively unimpeded through the plant. Both types enable efficient transport of materials within vascular plants.