Specialised plant cells (AQA GCSE Biology): Revision Notes
Specialised plant cells
Plant cells can become specialised to do specific jobs. This means they develop special features that help them work better at their particular task.
What is cell specialisation?
When plants grow, their cells change to become better at different jobs. This process is called differentiation.
Meristem cells are found at the tips of roots and shoots. These are unspecialised cells that can turn into any type of cell, making them the starting point for all plant cell specialisation.
- These unspecialised cells can turn into any type of cell
- As cells develop, they get different structures for specific functions
- Most plant cells keep the ability to differentiate throughout their life
Root hair cells
Root hair cells are found on the surface of plant roots. Their main job is to absorb water and mineral ions from the soil.
Key features of root hair cells
Root hair cells have several special adaptations:
- Large vacuole - this increases the rate of water absorption by osmosis
- Many mitochondria - these release energy needed for active transport of mineral ions
- Hair-like projections - these increase the surface area for better absorption
- Thin cell walls - allow water and ions to pass through easily
Worked Example: Surface Area and Absorption
A typical root cell might have a surface area of 1000 μm². When it develops hair-like projections, the surface area can increase to 5000 μm² or more. This 5-fold increase means the cell can absorb water and minerals much more efficiently.
The hair-like shape gives these cells a much bigger surface area, making them excellent at soaking up water and nutrients.
Xylem cells
Xylem cells form the transport tissue that moves water and mineral ions from the roots to all other parts of the plant.
Key features of xylem cells
Xylem cells have these special adaptations:
- Lignin in cell walls - this provides strength and support to the plant
- No end walls - allows water and ions to flow easily through the plant
- Hollow tubes - the cells die and become empty, creating clear pathways for water
- Thick, strong walls - prevent the tubes from collapsing under pressure
Unlike most plant cells, xylem cells are dead when they function. They sacrifice themselves to create hollow tubes for efficient water transport.
The lignin makes the cell walls very strong, which helps support the whole plant structure.
Phloem cells
Phloem cells form the transport tissue that carries dissolved sugars around the plant.
Key features of phloem cells
- Sieve plates - these are cell walls with holes that let sugars move between cells
- Companion cells - these contain lots of mitochondria to provide energy
- Living cells - unlike xylem, phloem cells stay alive to do their job
The companion cells help move the sugars through the sieve plates using active transport. This process requires energy, which is why these cells need so many mitochondria.
Why specialisation matters
Different plant cells become specialised because:
- Each job needs different features
- Specialised cells work more efficiently
- Plants can survive better with specialised cells
- It allows plants to grow bigger and more complex
Key Points to Remember:
- Plant cells specialise to do specific jobs more effectively
- Root hair cells absorb water and minerals using their large surface area and many mitochondria
- Xylem cells transport water and provide support with their lignin walls and hollow structure
- Phloem cells transport sugars using sieve plates and companion cells
- All specialised cells start as unspecialised meristem cells that differentiate as the plant grows