Permanent tissue: characteristics, types and functions

Gaurab Karki — Thu, 27 Jul 2017 03:08:29 +0000

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

I. Parenchyma

II. Collenchyma

III. Sclerenchyma

I. Parenchyma

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.

II. Collenchyma

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.

III. Sclerenchyma

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

i. Fibres:

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:

I. Xylem

II. Phloem

I. Xylem

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.

i. Trachieds:

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

ii. Vessels:

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

II. Pholem

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