Permanent Tissues: Its Types and Characteristics

Have you ever observed a plant cell through the microscope? 

It is very beautiful to see the arrangement of cells inside the plant body. 

Most of the cells which we observe under the microscope are the permanent tissues of plants. 

So what are Permanent tissues? 

The meristematic cells which lose their ability to divide will be specialised to perform specific functions and they are called permanent cells. These cells which lost their definite shape, size, functions and the power of division form the Permanent tissues. There are different types of permanent tissues.

Let’s take a deep dive into the details of Permanent tissues. 

Table of Contents

• Types of permanent tissues
• Simple permanent tissue
• Practice problems
• FAQs

Types of Permanent tissues

According to the type of cells present in the tissues, there are two types of permanent tissues as follows:

• Simple permanent tissues
• Complex permanent tissues

Simple Permanent Tissues

Permanent tissues which are made up of similar types of cells with the same structure and function are called simple permanent tissues. 

Types of Simple Permanent Tissues

Simple permanent tissues are of three types as follows:

• Parenchyma
• Collenchyma
• Sclerenchyma

Common Characteristics of Parenchyma

Parenchyma are the most commonly distributed tissues. They form the major component in all plant organs. They are simple living tissues. Parenchyma cells are generally isodiametric and their shapes vary from spherical, oval, round, polygonal to elongated. Their cells have thin walls made up of cellulose and have small intercellular spaces. They help in photosynthesis, storage of food and slow conduction of substances.

Common Types of Parenchyma

Based on the functions it perform parenchyma is modified into different types as follows:

Chlorenchyma

They are the parenchyma cells which contain chloroplasts and perform photosynthesis. Examples include mesophyll tissue of leaves. Mesophyll tissue can be divided into Spongy parenchyma and Palisade parenchyma.

Aerenchyma

Parenchyma tissue which possesses a network of interconnected gas conducting intercellular spaces are called Aerenchyma. It provides plant roots with oxygen under low oxygen conditions. It facilitates the movement of gases. Large intercellular spaces of aerenchyma provide buoyancy as seen in hydrophytes like lotus.

Prosenchyma

Prosenchyma is a specialised parenchyma having fibre-like, elongated slightly thick walled cells. It provides rigidity and strength.

Common Characteristics of Collenchyma

Collenchyma are made up of simple living cells. These cells have the deposition of cellulose, hemicellulose and pectin at corners. Hence the corners are thickened. Their shapes vary from oval, spherical to polygonal. They contain chloroplasts and no intercellular spaces present. They help in photosynthesis. They provide mechanical support to growing parts. They provide elasticity to plants. Collenchyma occurs below the epidermis in dicots as a homogenous layer or in patches. 

Common Characteristics of Sclerenchyma

Sclerenchyma cells are long and narrow. Cell walls are lignified with the presence of pits. Cells are dead. Protoplast is absent. Sclerenchyma cells are the chief mechanical tissue in the plants. It helps the plants to withstand compression, bending and shearing forces.

Types of Sclerenchyma Cells

Two types of sclerenchyma cells are present based on structure, origin and development. They are as follows: 

Fibres

Fibres are thick walled and elongated cells with pointed ends. The ends of adjacent fibres are interlocked. They generally occur in groups. 

Sclereids

Sclereids are short and highly thick walled cells. They are spherical, oval, cylindrical or irregularly shaped. They possess narrow cavities or lumen.

They are commonly found in the fruit walls of nuts, pear, sapota and guava pulp. They are also present in the seed coats of legumes and tea leaves. 

Types of Sclereids

Sclereids are of different types based on their shape and size as follows:

• Brachysclereids - They are also called stone cells. They are isodiametric cells. They have unbranched or branched pits. They are present in the pear and guava.

• Macrosclereids - They are elongated, columnar or rod-like cells. They are seen in the epidermal coverings of leguminous seeds.

• Osteosclereids - They are columnar cells with more or less dilated ends. They are present in the subepidermal cells of leguminous seeds.

• Astrosclereids - They are star shaped cells. They are commonly present in the leaves of aquatic plants.

• Filiform sclereids - They are fibre like. They are seen in olives. 
• Trichosclereids - They are long and hair shaped. They are hard needle-like branched cells found commonly seen in some species of plants that protect the plant from herbivores. Examples include the aerial root of Monstera.

Practice Problems of Permanent Tissues

Q1. Tissues are classified into two main types as permanent and meristematic tissues based on __________________.

• whether the cells formed are capable of dividing or not 
• Position and location 
• function, position and location
• structure, function, position and location

Solution: Plant tissues are classified into two main types as permanent and meristematic tissues on the basis of their ability to undergo cell divisions. Hence the correct option is a.

Q2. Identify the characteristic from the following that is absent in parenchyma? 

• It forms the major component within organs 
• They may be closely packed or will have small intercellular spaces
• The functions of parenchyma are photosynthesis, storage and secretion
• The walls of parenchyma are thick and made up of cellulose

Solution: The cell walls of parenchyma cells are thin and are formed of cellulose. The cells of parenchyma can be compactly packed or have small intercellular spaces. Hence the correct option is d.

Q3. The sclerenchymatous sclereids are found in ___________.

• fruit walls of legumes
• pulp of fruits like guava, pear, and sapota; leaves of tea
• Seed coat of nuts
• all of the above

Solution: The presence of a large number of sclereids results in the gritty texture of various plant parts such as fruit walls of legumes, pulps of fruits like guava, pear, and sapota, tea leaves, seed coat of nuts, etc. Hence the correct option is d.

Q4. In which of the following plant tissues, lignin is absent?

• Sclerenchyma fibres
• Sclereids
• Collenchyma
• Xylem tracheids

Solution: Collenchymatous cells, found below the epidermis are not lignified. The corner of the cells have cellulose, pectin and hemicellulose thickenings. Hence the correct option is c.

FAQs of Permanent Tissues

Question1.- What is the role of collenchyma cells in plants?

Anstion. Collenchyma is an example of a simple permanent living mechanical tissue. The components of the cell wall of collenchyma are pectin, cellulose and hemicellulose. These components give thickening in the corners of the cell. Pectin in the tissues provides mechanical support to the plant.

Question2.- Explain about the tissue that is most abundant in hydrophytes?

Anstion. Aerenchyma is the commonly found parenchyma cells in hydrophytes (plants that are found growing wholly or partially submerged in water), such as water lilies. Aerenchyma possesses an interconnected network of gas conducting intercellular spaces. It provides oxygen under low oxygen conditions in the plant roots. It facilitates the movement of gases. Large intercellular spaces of aerenchyma provide buoyancy also.

Question3.- What are the different types of sclerenchyma cells?

Anstion. Sclerenchyma cells are long and narrow cells that are lignified with the presence of pits. Sclerenchyma cells are the chief mechanical tissue in the plants. Two types of sclerenchyma cells based on structure, origin and development are fibres and sclereids. 

• Fibres - They are thick walled, elongated and have pointed ends. The ends of adjacent fibres are interlocked. They generally occur in groups. 
• Sclereids - They are short, highly thick walled cells. They are spherical, oval, cylindrical or irregularly shaped. They possess narrow cavities or lumen. They are present normally in the fruit walls of pear, sapota, nuts and pulp of guava. They are also present in the seed coats of legumes and tea leaves. 

Question4.- Which is the photosynthetic parenchyma cell and explain why?

Anstion. Chlorenchyma are the parenchyma cells which can perform photosynthesis. It possesses chloroplast. Examples of chlorenchyma cells include mesophyll tissue of leaves. Mesophyll tissue can be divided into spongy parenchyma and palisade parenchyma in dicot leaves.

Related Concepts to Permanent Tissues in Biology

• Phloem
• Permanent Tissues Xylem

NCERT Class 11 Biology Chapters