Characteristics and functions of the Support Tissues
Parenchyma
Located in the cortex and pith.
The cells are spherical or elongated.
The cells are unspecialized, living and have thin walls made of cellulose.
Functions
- Give support in herbaceous plants (when turgid).
- Packing (main function)
- Storage tissue (store starch)
Collenchyma
Found below the epidermis.
The cells are living.
Their walls are thickened with cellulose, especially at the corners to provide mechanical support.
The cells are elongated and not lignified.
Provide mechanical support in leaves, herbaceous plants and young woody plants.
Sclerenchyma
The cells have thickened and lignified walls.
The cells are long and tapering.
Sclerenchyma cells are often long fibres in stems such as hibiscus.
Sclerenchyma consists of dead cells thickened by lignin.
Lignin is a complex polysaccharide.
It is the main constituent of wood.
Provide mechanical support.
Xylem
Consists of tracheids and vessels.
Their walls are lignified and hence dead.
The cells are elongated and connected end to end forming a continuous column.
Function
- Offer mechanical support.
- Conduct water and mineral salts from the roots to other parts of the plant.
Vessels have lignin is distributed unevenly in rings, spirals or patches on their walls.
Xylem vessels
Xylem tracheids
