1.5

• Root hair cells


  • Greatly increase the surface area available for water to move into the cell
  • Have a large permanent vacuole that speeds up the movement of water by osmosis from the soil across the root hair cell
  • Have many mitochondria that transfer the energy needed for the active transport of mineral ions into the root hair cells
• Xylem cells


  • The xylem cells are alive when they are first formed but a special chemical called lignin builds up in spirals in the cell walls. The cells die and form long hollow tubes that allow water and mineral ions to move easily through them, from one end of the plant to the other
  • The spirals and rings of lignin in the xylem cells make them very strong and help them withstand the pressure of water moving up the plant. They also help support the plant stem
• Phloem cells


  • The cell walls between the cells break down to form special sieve plates. These allow water carrying dissolved food to move freely up and down the tubes to where it is needed
  • Phloem cells lose a lot of their internal structures but they are supported by companion cells that help to keep them alive. The mitochondria of the companion cells transfer the energy needed to move dissolved food up and down the plant in phloem
• Photosynthetic cells


  • They contain specialised green structures called chloroplasts containing chlorophyll that trap the light needed for photosynthesis
  • They are usually positioned in continuous layers in the leaves and outer layers of the stem of a plant so they absorb as much light as possible
  • They have a large permanent vacuole that helps keep the cell rigid as a result of osmosis. When lots of these rigid cells are arranged together to form photosynthetic tissue they help support the stem. They also keep the leaf spread out so it can capture as much light as possible
• A cell within the trunk of a tree cannot carry out photosynthesis
• Identifying the function of an unknown specialised plant cell

  1. Look for features such as the presence of chloroplasts, large vacuoles, spiral thickenings in cell walls, sieve plates, etc.

  2. Consider the location of the cell within the plant

  3. Relate the observed features to the known functions of specialised plant cells