Permanent Tissues | Class 9 Biology

The smallest and basic unit of life that carries out all the life processes is known as the cell  A group of cells that are similar in structure and work together to achieve a specific function., are known as tissues. Plants and animals are made of different organs and these organs are made of tissue.  Plant tissue can be divided into two types: Meristematic tissue and Permanent tissue

Permanent Tissue

Meristematic tissues divide and rise to form permanent tissue, which takes permanent shape, size, and function through the process of differentiation. They are found in almost all plants that are matured mainly below the epidermis. They have spread around in layers of cells. Parenchyma is found in the cortex of the stem and roots and in the mesophyll of leaves. Collenchyma is found in the leaf stalk and leaf midribs below the epidermis. Sclerenchyma is found in stems, around the vascular bundle, around the hard covering of seeds and nuts, and in veins of leaves. Complex tissue xylem is found throughout the plant body, the center of the vascular bundle, and phloem is found outside the vascular bundle, in leaf veinlets, and in the innermost layers of the bark of old trees. These can be further divided into:

• Simple Tissues
  • Parenchyma
  • Collenchyma
  • Sclerenchyma
• Complex Tissues
  • Xylem 
  • Phloem
  • Secretory tissue

Simple Permanent Tissue

Cells that are more or less similar form simple tissue. They are also called homogeneous tissues.

Parenchyma 

They are also known as packing tissue. These are the most common tissue which has spherical, thin-walled, inter-cellular spaces and large vacuoles cell. Their chief function is to manufacture and store food. it makes up the chloroplast-laden mesophyll (internal layers) of leaves and the cortex (outer layers) and pith (innermost layers) of stems and roots and it also forms the soft tissues of fruits.

Types of Parenchyma

1. Chlorenchyma: Parenchyma which contains chlorophyll and helps in photosynthesis is known as chlorenchyma 
2. Aerenchyma: Parenchyma which contains air cavities and is present in aquatic plants is known as aerenchyma. It provides buoyancy to aquatic plants. They help in the formation of the anaerobic rhizosphere in anaerobic soil.

Collenchyma

These tissues are made of living and elongated cells which are irregularly thickened at the corners due to mechanical stress on plants. They provide flexibility and mechanical support to the plant. It helps various parts of plants to bend without breaking them .they are always found beneath the epidermis. They produce new cells and help in the elongation of the stem. They are mostly found in monocot plants such as palm, coconut, etc. collenchyma contains cellulose, hemicelluloses, and pectic materials. It may or may not contain a few chloroplasts and may perform photosynthesis and store food.

Types of Collenchyma

1. Tangential Collenchyma– In this collenchyma Cells are thickened at the tangential face of the cell wall and arranged into lined-up rows.
2. Lacunar Collenchyma– In this collenchyma, they have space within the cells.
3. Angular Collenchyma– In this collenchyma, the intercellular contact points are thickened.
4. Annular Collenchyma– in this collenchyma, cell walls are thickened uniformly.

Sclerenchyma

These tissues are made up of long and narrow dead cells without any inter-cellular space. Due to the presence of lignin, their cell wall is thick. It adds mechanical strength to the plant. These are present in the stem, around the vascular bundle, in the veins of leaves, and in the hard covering of seeds and nuts.

Types of Sclerenchyma

• Fiber: They have long cells which provide strength to the plant. They are often found in bundles or strands and can be present almost anywhere in the plant body, including the stem, the roots, and the vascular bundles in leaves. They provide the raw material for various textile products and woven materials .they are mostly found in clusters, clumps, or patches.
• Sclereids: They are found in very different shapes and can be found in tissue such as the periderm, cortex, pith, xylem, and phloem. They are present in various plants such as the outer covering of nuts and many seeds. the grainy texture of pears and guavas is also due to this.

Difference between Parenchyma, Collenchyma, and Sclerenchyma

Parenchyma	Collenchyma	Sclerenchyma
The cells are living and thin-walled.	The cells are living and thick at the corners.	The cells are dead and thick-walled due to lignin deposition.
The cells are oval, spherical, or polygonal in shape.	The cells are elongated and thickened at the corners.	The cells are long and narrow.
There is a large intercellular space between the cells.	There is very little intercellular space.	There is no intercellular space.

Complex Permanent Tissue 

Vascular tissues which are made up of different types of cells that work together and help in the transportation of food, water, and minerals throughout the plant, are known as complex tissues.

Xylem

It is mostly made up of dead cells and is used to transport water and mineral from root to leaves and other parts of the plant. It contains tracheids, vessels, xylem parenchyma, and xylem fibers. Out of all these only, the Xylem parenchymas is made up of living cells and contains food. The tracheid and vessels are long, elongated, and hollow.

Phloem

It is made up of living cells and helps in the transportation of food from leaves to other parts of plants. It is made up of sieve tubes, companion cells, phloem fiber, and phloem parenchyma. Out of all these, only phloem fiber is made up of dead cells. They are also responsible for the transportation of proteins and mRNAs.

Secretory Tissues

As the name indicates these tissues are related to the secretion of substances such as gums, raisins, latex, nectar, etc.

Types 

• Laticiferous Tissues-They long, elongated, thickened, and multi-nucleated cells and also contain a yellowish substance called latex. they are spread over the parenchyma cells of plants. 
• Glandular Tissues-This tissue contains glands. these glands either contain secretory or excretory products. These tissues secrete various essential things like essential oils, mucilage (in betel leaf), gum, resin, tannin, digestive enzymes, etc.

FAQs on Permanent Tissues

Question 1: What is permanent tissue made up of?

Answer:

Permanent tissue is made up of meristematic tissue. which take permanent shape, size, and function through the process of differentiation. they are nondividing cells .they are of three types: parenchyma, collenchyma, and sclerenchyma.

Question 2: What are the types of plant tissue?

Answer:

Different types of plant tissue:

• Meristematic tissues: contains cells that continuously undergo repetitive division. they are responsible for plant growth. they are of three types: apical meristem, lateral meristem, and intercalary meristem.
• Permanent tissues: meristematic tissues divide and rise to form permanent tissue, which takes permanent shape, size, and function through the process of differentiation. They are of three types: parenchyma, collenchyma, and sclerenchyma.

Question 3: Differentiate between Xylem and Phloem.

Answer:

Xylem	Phloem
It contains all dead cells except the xylem parenchyma.	It contains all living cells except phloem fibers.
Cell walls are thick.	Cell walls are thin.
It transports water and minerals.	It transports foods and proteins.
Tracheids and vessels are the main elements of this tissue.	Sieve tubes and companion cells are the main elements of this tissue.

Question 4: Permanent tissues are located in?

Answer:

Permanent tissue is found in almost all the plants which are matured mainly below the epidermis. 

• Parenchyma is found in the cortex of the stem and roots and in the mesophyll of leaves. 
• Collenchyma is found in the leaf stalk and leaf midribs below the epidermis. 
• Sclerenchyma is found in stems, around the vascular bundle, around the hard covering of seeds and nuts, and in veins of leaves.
• Complex tissue xylem is found throughout the plant body, the center of the vascular bundle, and phloem is found outside the vascular bundle, in leaf veinlets, and in the innermost layers of the bark of old trees. 

Question 5: What are the functions of permanent tissue?

Answer:

• The function of permanent tissue is to provide mechanical strength and support to the plant
• It also helps in the transportation of water, mineral, and food .it also manufacture and  stores food 
• It helps various parts of plants to bend without breaking them 
• They also secrete various substance such as gum, latex, nectar, etc