Like a human body, plants also have tissues known as Permanent Tissue. The tissues provide structural strength to the plants. Permanent tissues have fully matured and have no capacity to divide further. The meristematic tissues divide to generate the permanent tissues.

The metabolic rate in permanent tissues is less compared to other tissues. Most plant tissues are dead since dead cells can provide mechanical strength as easily as live ones and need less maintenance. This article includes the definition, types of permanent tissues, permanent tissue diagram, flow chart and frequently asked questions related to this topic.

Permanent Tissue Definition

A Permanent tissue is defined as a group of mature and differentiated cells that have lost the capacity of cell division either permanently or temporarily. In simple terms, the permanent tissue of a plant contains nondividing cells, and each cell has certain functions in a plant. Meristematic tissue gives rise to the cells of permanent tissue. 

What is Permanent Tissue?

Depending upon the capacity to divide, plant tissues are broadly classified into two types, namely, Meristematic tissue and Permanent tissue.

Permanent tissue cells are completely matured, larger in size, and have a specific shape. The metabolic rate of cells in these tissues is lower in comparison to other tissues.

Permanent Tissue Flowchart

The permanent Tissue flowchart is given below:

Types of Permanent Tissues

Permanent tissues are classified into three kinds based on their structure, origin, and function.

1. Simple Permanent Tissue
2. Complex Permanent Tissue
3. Special Permanent Tissue

1. Simple Permanent Tissue

Tissues which are made up of similar cells structurally and functionally are called simple permanent tissue. It is a collection of linked cells that perform a certain job. There is only one type of cell in them. All of the cells that make up the tissue are similar in structure and have comparable elements. They are homogeneous and made up of physically and functionally similar cells. Simple tissues are of three types: Parenchyma, Collenchyma, and Sclerenchyma.

(a) Parenchyma

Parenchyma is a simple permanent tissue made up of thin-walled, loosely arranged living cells with intracellular space.

Characteristics of Parenchyma

1. The cells are oval, cylindrical, spherical, rectangular, polygonal and isodiametric in shape.
2. Each cell has a thin cell wall made up of cellulose. Each cell has a centrally situated vacuole, the peripheral nucleus which is very small in size and dense cytoplasm.
3. Parenchyma is found in all parts of a plant. 
4. The cells are loosely arranged with intercellular space. On the basis of their origin, intercellular spaces are of two types – Schizogenous and Lysogenous.

Types of Parenchyma

Parenchyma cells are modified and classified to perform a variety of functions. These functions are mentioned in the following figure.

(b) Collenchyma

Collenchyma is a simple permanent living mechanical or supporting tissue. It is a modified parenchyma. Schleiden discovered and coined the term “Collenchyma” in the year \(1830.\)

Characteristics of Collenchyma

1. Collenchyma cells have thick deposits of cellulose, hemicellulose and pectin in their cell walls and appear polygonal in cross-section. Each cell is compactly arranged with outer intercellular space.
2. Each cell has a centrally situated vacuole, peripheral nucleus and dense cytoplasm. These cells are found below the epidermis in the petiole of leaves and stems.

Collenchyma is the only living, mechanical permanent tissue. Depending on the thickening, there are three types of collenchyma, lamellar, lacunate, and angular.

(c) Sclerenchyma

Sclerenchyma is a simple permanent dead mechanical tissue. Mettenius discovered and coined the term sclerenchyma in the year \(1805.\)

Characteristics of Sclerenchyma

1. It is made up of thick-walled, compactly arranged cells without intercellular space.
2. The walls are thick due to the deposition of lignin as a secondary wall. Sclerenchyma cells are seen in hard parts of fruits and nuts, seed coat, etc.
3. Sclerenchyma helps plants with mechanical support and provides rigidity.

Types of Sclerenchyma

The sclerenchyma is of two types and is as follows:

a. Sclerenchyma Fibre – These are the longest, hardest sclerenchyma cells with pointed ends. The cell wall of fibre is lignified with narrow lumen and pits. The fibres are dead at maturity. They have great tensile strength, flexibility and elasticity.
b. Sclereids – Sclereids are short, thick-walled lignified isodiametric and are irregularly shaped dead cells of sclerenchyma. These are also known as stone cells or sclerotic cells. The term ‘sclereid’ was given by Tscherch in the year \(1885.\)

2. Complex Permanent Tissue

These complex permanent tissues are heterogeneous tissues containing living and dead cells, thin-walled or thick-walled cells having a common origin and performing a definite function.

Complex Permanent Tissues are the conducting tissues and also known as vascular tissues and, classified as xylem and Phloem.

Fig:  Water and Food Flow in Xylem and Phloem

(a) Xylem

It is a complex permanent tissue mainly performing the function of conduction of water and solutes from the roots up to the top of plants. Simultaneously, it provides strength to the plants.

Components of Xylem

The components of the xylem are given below with respective images:

On the basis of the time of origin, Xylem is classified as follows:

i. Protoxylem – It develops first from procambial strands, consists of smaller tracheids and vessels.
ii. Metaxylem – It develops in a later stage. It consists of large tracheids and vessels.

The arrangements of protoxylem and metaxylem may be of the following types:

1. Exarch condition is when the protoxylem is towards the periphery and the metaxylem towards the centre. This is seen in the roots.
2. Endarch condition is when the protoxylem is towards the centre and the metaxylem is towards the periphery. This is found in the stem.
3. Mesarch condition is when the metaxylem surrounds the protoxylem. This is found in the leaves.

On the basis of the position of protoxylem with respect to metaxylem.

(b) Phloem

It is a complex permanent heterogenous food conducting tissue. It conducts the organic food from leaves to other parts of the plant body. It consists of both living and dead cells.

It consists of four components. A new cell type called transfer cells has recently been reported from the Phloem. Transfer cells are much-folded cells that are adjacent to sieve cells. They provide a large area for the transfer of solutes.

Components of Phloem

The four components of the Phloem is given below:

What are Protophloem and Metaphloem?

i. Protophloem – It is the first formed part, which develops in plants that are undergoing enlargement. During the elongation process, the protophloem elements get stretched and hence, become non-functional.
ii. Metaphloem – It is the late-formed part of the primary Phloem when they stop enlargement.

3. Special Permanent Tissues

These cells or tissues are also known as Secretory tissues and are specialized to secrete or excrete products. The secreted products may be useful or may not be useful for the plants.

Types of Special Permanent Tissue

These tissues are of two types, namely, Glandular tissues and Laticiferous Tissues.

(a) Glandular Tissues

These are present in the form of glands and are of two types, external glands and internal glands.

i. External glands are of three types, Glandular heir, digestive glands and secreting glands.
ii. Internal glands are also of three types, oil-secreting, resin secreting and water secreting glands.

(b) Laticiferous Tissues

These tissues are special tissues that contain a colourless milky or yellow coloured fluid called latex. These cells are scattered throughout the ground tissue of the plant and contain stored organic matter in the form of rubber, starch, alkaloids, tannins, mucilage, proteins, enzymes, etc.

Functions of Permanent Tissues

The functions of Permanent tissues are as follows:

1. The permanent tissues store the food materials such as starch, proteins, fats and oils.
2. They show essential metabolic functions like respiration, photosynthesis, secretion, etc.
3. Chlorenchyma helps in photosynthesis, and aerenchyma helps in buoyancy and gaseous exchange.
4. The permanent tissues provide rigidity to young parts of the plants.
5. Collenchyma protects the vascular bundle by forming a bundle sheath or cap in dicot leaves.
6. Parenchyma fibres form a raw material in the jute and textile industries.
7. Phloem fibres are also used as raw materials in textile and cottage industries.
8. Xylem is needed for the ascent of sap from roots to the leaves.
9. Phloem is needed to translocate food to various parts of the plant.

Permanent Tissues: Characteristics 

1. Permanent tissues can be both living or dead.
2. Cell walls of permanent tissue can be thin or thick, and ergastic compounds are found in each cell.
3. The nucleus is small in comparison to the rest of the cell.
4. The rate of metabolic activity is relatively slow.
5. There is intercellular space between the cells.
6. The amount of cytoplasm in the body is quite small.
7. Reserve, excretory, and secretory chemicals may be found in cells.
8. Foods that are permanently preserved in tissue.
9. Chlorophylls are a type of permanent tissue that creates food.
10. Reserve, excretory, and secretory chemicals may be found in cells.
11. The presence of vacuoles is noticeable.
12. At maturity, protoplasm may or may not be present in the cells.

Summary

Permanent tissue is one type of plant tissue that has a definite shape and size and is generally devoid of the ability to divide. These tissues are classified as simple, complex and special permanent tissues. These cells have their uniqueness and functions and help in the growth and development of a plant. We have understood permanent tissues, types of permanent tissues, and their functions through this article.

FAQs on Permanent Tissue:

Following are the frequently asked questions on permanent tissue:

Q.1: Where is permanent tissue found?

Ans: The permanent tissue is found in all matured plants, mainly below the epidermis of the leaves.

Q.2: What are the functions of permanent tissues?

Ans: The function of permanent tissues are as follows:

(a) The permanent tissues store the food materials such as starch, proteins, fats and oils.

(b) They show essential metabolic functions like respiration, photosynthesis, secretion, etc.

(c) The permanent tissues provide rigidity to young parts of the plants.

Q.3: What is complex permanent tissue?

Ans: Complex permanent tissues are heterogeneous tissues containing living and dead cells.

Q.4: What are permanent tissues and their types?

Ans: Permanent tissue is defined as a group of mature and differentiated cells that have lost the capacity of cell division either permanently or temporarily. Permanent tissues are of three types, are as follows:

(a) Simple Permanent Tissue

(b) Complex Permanent Tissue

(c) Special Permanent Tissue

Q.5: What is simple permanent tissue?

Ans: Tissues which are made up of similar cells, structurally and functionally, are called simple permanent tissue.

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