Permanent tissue: characteristics, types and functions
Characteristics of permanent tissue:
- Permanent tissues are derivatives of meristematic tissue
- They are mature tissue and the cell have lost the capacity of cell division.
Types of permanent tissue
- Simple permanent tissue
- Complex permanent tissue
- Secretory tissue
1. Simple permanent tissue
- Simple permanent tissue is composed of single type of cells which have similar origin, structure and function.
Types of simple permanent tissue
Characteristics of parenchyma tissue
- Living tissue
- Shape: each cell is spherical, oval, rectangular, polygonal, elongated or irregular in shape
- Cell wall: thin walled made up of cellulose, hemicellulose and pectin
- Young Parenchymatous cells are loosely arranged
- Intercellular space : present
- Food storage: cell store reserve food material
- Parenchyma is found in all parts of plant such as cortex, pith, palisade, mesophyll, flower, seed etc
- It is also found in vascular tissues.
Types of parenchyma tissue
i. Prosenchyma: it is long and tapering parenchymatous cell present in some plants. Eg pericylce
ii. Aerenchyma: it is a type of parenchyma cell having large intercellular air space. Eg present in cortex of hydrophytes
iii. Chlorenchyma: it is a parecnhyma cell containing chloroplasts. Eg present in palisade of leaves and helps in photosynthesis
Function of parenchyma tissue:
- Photosynthesis: chlorenchyma contains chloroplast which helps in photosynthesis
- Storage: parenchyma cell stores food in the form of starch, proteins, oils and fats.
- Buoyancy: helps in floating of aquatic plants due to presence of aerenchyma tissue
- Secretion: Idioblastic cell secretes resins, latex, tannin, oils etc
- Transport: parenchyma of xylem and phloem helps in transport of nutrition and water.
- Mechanical support: Prosenchyma tissue provide mechanical support.
Characteristics of collenchyma tissue:
- Living tissue
- Shape: each cell is somewhat elongated
- Cell wall: thick walled due to deposition of hemicellulose and pectin in intercellular space
- Intercellular space: present or absent
Types of collenchyma tissue:
i. Angular collenchyma: thick cell wall at corner of cell; without intercellular space
ii. Lacunar collenchyma: thick wall at boarder of cell; large intercellular space
iii. Plate or lamellar collenchyma: thick wall at tangential wall; without intercellular space
Functions of collenchyma tissue
- Mechanical support: It is living mechanical tissue
- Photosynthesis: It contain chloroplast and carry out photosynthesis.
Characteristics of Sclerenchyma:
- Dead tissue
- Shape: elongated and pointed at both end
- Cell wall: thick and lignified
- Cell lack protoplasm
- It gives strength and rigidity to the plant body
Types of sclerenchyma tissue
- it is thick walled,long and pointed dead cell
- Cell wall contains simple, oblique or bordered pits.
- Present in xylem, covering of fruits
- Gives mechanical supports
ii. Sclereids (stone cell):
- extremely thick walled cell with spherical, oval or dumbbell shape.
- Cell wall contains simple pits
- Present in hard part of plants, pulp of fruits
- Provide local mechanical supports
Function of sclerenchyma tissue
- Mechanical support: sclerenchyma is made up of dead and lignified cells which provides support to plants.
- Provides hardness to stony fruits such as nuts, coconut, almond etc
2. Complex permanent tissue
- Complex permanent tissue is composed of two or more than two types of cells and contribute to a common function.
- It is also known as vascular tissue
Types of complex tissue:
- The function of xylem is to transport water and minerals from the root to the leaves of plants.
- It also provides support to plants.
- Xylem is also known as wood
- Xylem is composed of four types of cells-Tracheids, Vessels, Xylem fibres and Xylem parenchyma.
- Trachieds are elongated cell with tapering end
- They are dead cells with lignified cell wall
- Function: conduction of water and minerals from root to leaves and also provide mechanical support
- Types: annular, spiral, reticular, sclariform and pitted
- Vessels are long, cylindrical, tube like dead cells
- Vessels are main element of xylem for conduction
iii. Xylem fibres:
- They are sclerenchymatous cell
- They are dead cells
- They provide mechanical support
iv. Xylem Parenchyma:
- They are parenchymatous cell
- They are living cells
- Function: storage of food in the form of starch or fat
- Phloem is responsible for the conduction or transport of organic food synthesized by the s to different part of plant body.
- Phloem is also known as bast.
- Phloem is composed of four types of cells-Sieve tubes, Companion cells, Phloem parenchyma and Bast fibres
i. Sieve tubes
- They are tube like structure composed of elongated cell arranged by end to end
- Sieve element or cell lack nucleus
- Function: transport of organic food from leaves to different parts
ii. Companion cells:
- They are thin walled, elongated living cells.
- Each cell contains large nucleus
- Companion cell are present only in angiosperm
- Function: support sieve cell in conduction of food.
iii. Phloem parenchyma:
- They are living parenchymatous cells
- Function: storage of food in the form of starch or fat. It also store tannin and resins
iv. Bast fibres:
- They are sclerenchymatous cell.
- They are dead cells.
- Function: mechanical supports
3. Secretory tissues
- Secretory tissues are specialized tissue having secretory functions
- They secretes various types of chemicals.
Types of secretory tissue
I. Lactiferous tissues:
- It is thin walled tubes like tissue which produce latex (milky juice).
- They are parenchymatous cells
- Some plants having these tissue are Ficus (Bar, Peepal), Euphorbia (Lalupate), Rubber plant, Papaya, etc.
II. Glandular tissue:
- This tissue forms glandular structure which secrete or excrete chemical substances.
- These glands are present on the epidermis
- Some plant having glandular tissue are Betel plant (mucilage), lemon , orange (oil), Sundew, Venus fly, Pitcher plant etc