Root hair cells help plants to take up water and mineral ions more efficiently and are relatively close to the xylem tissue, which carries water and mineral ions up into the rest of the plant. Mineral ions are moved into the root hair cell by active transport. Root hair cells have 3 main adaptations:
- greatly increase surface area available for water to move into cell
- have large permanent vacuole that speeds up movement of water by osmosis from soil across root hair cell
- many mitochondria that transfer energy needed for active transport of mineral ions into root hair cells
Many plant cells carry out photosynthesis. Photosynthetic cells usually have lots of adaptations:
- contain specialised green structures, chloroplasts, containing chlorophyll that trap light needed for photosynthesis
- usually positioned in continuous layers in leaves and outer layers of stem of plant so absorb as much light as possible
- large permanent vacuole helps keep cell rigid as result of osmosis
Xylem is the transport tissue in plants that carries water and mineral ions from roots to highest leaves and shoots and is also important in supporting plant. The xylem is made up of xylem cells that are adapted to their functions:
- xylem cells are alive when they are first formed but special chemical called lignin builds up in spirals in cell walls. cells die and form long hollow tubes that allow water and mineral ions to move easily through them from one end of plant to other
- spirals and rings of lignin in xylem cells make them very strong and help withstand pressure of water moving up plant.
Phloem is specialised transport tissue that carries food made by photosynthesis around body of plant. made up of phloem cells that form tubes rather like xylem cells, but do not become lignified and die. dissolved food can move up and down phloem tubes to where needed. adaptations of phloem cells:
- cell walls between cells break down to form special sieve plates which allow water carrying dissolved food to move freely up and down tubes to where needed
- phloem cells lose a lot of internal structures but are supported by companion cells that help keep them alive. mitochondria of companion cells transfer energy needed to move dissolved food up and down plant in phloem
