1.5 Specialisation in plant cells

• Like animals, plants have specialised cells to carry out their funtions. Specialised plant cells form part of tissues, organs, organ systems, or their whole organisms
• Root hair cells occur near the tips of roots. They increase the surface area of the root so that it can absorb water and mineral ions efficiently. Root hair cells are close to xylem tissue that transports water and mineral ions through the plant.
• Root hair cells:

  • Greatly increase the surface area avaliable for water to move into the cell
  • Have a large permanent vacuole- this speeds up the movement of water by osmosis from the soil across the root hair cell
  • Have many mitochondria- these transfer the energy needed for the active transport of mineral ions into the root hair cells
• What is the main function of a root hair cell?


  To take up water and mineral ions from the soil
• Plants can make their own food by photosynthesis. Pbotosyntheic cells:

  • Have chloroplasts containing chlorophyll to trap the light needed for photosynthesis
  • Are often found in continuous layers in the leaf and outer layers of stems
  • Have a large permanent vacuole that helps keeps the cell rigid
• The xylem tissue has two main functions

  1. The xylem cells transport water and mineral ions from the roots to the stem and leaves
  2. Xylem tissue supports the plant
• • Xylem cells are living when they are first formed
  • Then a chemical called lignin builds up in spirals in the call walls.
  • The cells die, leaving long hollow tubes. Water and mineral ions can move up the tubes
  • The spirals and rings of lignin make the tubes of xylem very strong
• Phloem is the tissue that transports food made by photosynthesis to the rest of the plant. Phloem cells form tubes but do not become lignified like the xylem.

  • The cell walls between phloem cells break down to form sieve plates.
  • Phloem cells lose a lot of their structure but are kept alive by companion cells
  • The companion cells contain mitochondria that transfer energy to aid the movement of dissolved food in the phloem
• Name the chemical that makes Xylem rigid

  Lignin