Tissue
A group of cells that are similar in structure and work together to perform a particular function form a tissue.
Types of Meristematic tissues
- Apical - Growing tips (i.e.) roots and shoots.
- Lateral - Girth or width of the stem or root.
- Intercalary - Located near nodes.
Meristematic Tissue dont have…
[ Name the cell organelle ]
Vacuoles
[ As they are growing and dividing, they lack vacuoles ]
Parenchyma
[ Structure, Function & Location ]
Structure:
- Living
- Oval in shape
- Thin cell wall
- Large intercellular space
Function:
- Storage of food
- Chlorenchyma - Photosynthesis
- Aerenchyma - Aquatic plant float (buoyancy) - Large air cavities
Location:
- Most commonly found
- Root cortex, Leaf mesophyll
Collenchyma
[ Structure, Function & Location ]
Structure:
- Living
- Elongated
- Irregularly thickened
- V.less Intercellular space
Function:
- Flexibility in plants
- Bending of tendrils and stems without breaking
Location:
- Leaf stalks, tendrils, stems of climbers.
Sclerenchyma
[ Structure, Function & Location ]
Structure:
- Non-Living
- Long, narrow
- Thickened by lignin
- No Intercellular space
Function:
- Mechanical Strength
- Hardness
Location:
- Stems, around vascular bundle
- Hard covering of seeds/nuts
Why is the epidermis much thicker in plants of dry habitats?
To prevent water loss by Transpiration.
Why do root epidermal cells have hair-like projections?
To increase the water absorptive surface area.
Cutin
[ Location & Function ]
- Cutin is a waxy substance that forms a layer called cuticle, and is present in epidermis of young plants.
- It is water-resistant and prevents waterloss, protects from mechanical injury.
How is Cork formed?
As the plant grows older, the secondary meristem in cortex forms a layer of cells which make the cork.
Suberin
[ Location & Function ]
- Suberin is the waxy substance present in root cork cells of old plants.
- It makes the stem impervious to water & gases.
Xylem - Mention its Parts
- Tracheids
- Vessels
- Xylem Parenchyma
- Xylem Fibres
Xylem - Explain its Parts
- Tracheids and vessels are tubular structures. They transport water and minerals (vertically).
- Xylem parenchyma stores food.
- Xylem fibres act as support.
Phloem - Mention its Parts
- Sieve cells
- Sieve tubes
- Companion cells
- Phloem fibres
- Phloem parenchyma
Phloem - Explain its Parts
- Sieve tubes are tubular cells with perforated walls. They transport food. They dont have nucleus but are living.
- Companion cells regulate the movement of food.
Basement Membrane
[ Function & Location ]
- Made up of extracellular fibres.
- Seperates epithelial tissue from underlying tissues.
- Lies below the epithelium.
Types of Epithelium
- Simple squamous epithelium
- Stratified squamous epithelium
- Columnar epithelium
- Cuboidal epithelium
Simple Squamous Epithelium
[ Structure & Location ]
Structure:
- Extremely thin & flat.
- Form a delicate lining.
Locations:
- The oesophagus, lining of mouth, blood vessels, lung alveoli.
Why is the simple squamous epithelium present in blood vessels?
Transportation of substances occurs through the thin selectively permeable surface of the simple squamous epithelium.
Stratified Squamous Epithelium
[ Structure & Function ]
- Squamous stacked in a pattern of layers.
- Present in skin.
Columnar Epithelium
[ Structure, Function & Location ]
Structure:
- Tall, pillar-like cells
- Columnar tissue also has cillia ( in respiratory tract ) to push mucus.
Location:
- Present wherever there is absorption and secretion.
- Inner lining of intestine, respiratory tract.
Cuboidal Epithelium
[ Structure, Function & Location ]
Structure:
- Cube shaped cells
Function:
- Mechanical support
Location:
- Lining of kidney tubules, ducts of salivary glands.
How is a glandular epithelium formed?
Glandular Epithelium is formed when a portion of cuboidal epithelium folds inwards to form a multicellular gland. This gland is able to secrete substances.
Types of Matrices
[ Matrix ]
Jelly-like, Fluid, Dense, Solid
