A.PARENCHYMA TISSUES
- They consist of living cells that are elongated in shapes. They can divide to give new cells and place a part in secondary growth
- They act as packaging tissues and when turgid provide support for the plant
- The tissues function mainly in providing support, photosynthesis and pollination. They have air spaces which thin cellulose cell walls which allow for interring of water and mineral salts that account for turgidity
- They have large cells which large vacuoles that provide storage space for starch
- Some parenchyma cell contains chromoplasts especially in the petals which help to produce pigments that make them attractive to insects. Hence helping for pollination and dispersal
Fig:
B.SCLERENCHYMA
Mature sclerenchyma cells consist of death cell with lignified walls, this is a supporting tissue made up of cells whose primary walls have been heavily and uniformly thicken with cellulose and lignin both of which provide support. The cellulose and lignin are secreted by the protoplast, these thickening help cell to pack well to enable firmness and give the necessary mechanical support of the plant.
There are 2 twin type of sclerenchyma: sclereids and fibres, but the different between the two is not always clear cut:
a.Sclereids or stone cells
- There are widely distributed in plants
- Their works are heavily lignified and contain numerous branching pits
- Sclereids are more spherical in shape and are found in groups or singing in roots, stems, leaves of plants or seed where they form the hard cover
- Sclerenchyma fibres
- They are elongated cells which are often grouped in strands or skeatts streath
- They have great tensile strength and do not break easily when stretched e.g. hemp, and flax, all of which are of economic importance
- Fibres are often found in a vascular bundle of dicot and monocot
- COLLENCHYMA
- It is made up of living cells whose primary cell wall is unevenly thicken which cellulose and pectic substances
- cells are polygonal which tapering ends
- Bits are present in the walls and it is self and plastic
Function
- In the mechanical support especially in long stein where plasticity is necessary to accommodate changing growth requirements
- Distributed in the outer region of cortex in young stems and in midribs of leaf petiole
