What are the types of plant tissue?

Todays topic for class 7 biology chapters ICSC is What are the types of plant tissues? This chapter has two parts. To check the part 1 of this chapter click on this link : https://lessonstobelearneda-z.blogspot.com/2022/05/the-plant-tissue.html

Diagram of plant tissue

Plant tissue

What are permanent tissues?

The tissues consisting of non-dividing cells are known as permanent tissues. They perform particular functions and are derived from meristematic tissues. They can't divide themselves and are found at fixed positions in the plant body.These are of two types -

1.Simple permanent tissue

2.Complex permanent tissue

What is Simple Permanent Tissue?

They are composed of similar cells that have similar structure and functions. These tissues help in providing support and protection to the plants. These are of two types -

(a)Protective Tissue - It consists of epidermis and cork.

*Epidermis - It is present on the outermost side. It consists of thick walled cells. Epidermis has thick outer walls which are covered with organic substances such as cutin. Cutin helps in reducing water loss by transpiration.

*Cork - Cork is also a type of protective tissue which is found at the periphery of stem and root when they grow old with time. It consists of dead cells with thick walls.

(b) Supporting Tissue - It consists of -

*Parenchyma

*Collenchyma

*Schlerenchyma

*Parenchyma - Cells have thin walls, living and are round, polygonal or oval in shape. Cells are packed loosely and consists of cytoplasm, a large vacuole in the centre and a prominent nucleus. Intercellular spaces are found between the cells. It is mostly found in xylem, phloem, leaves, stem and roots. Parenchyma cells having chloroplasts found in leaves help in the process of photosynthesis. These are known as chlorenchyma. Its main functions are -

•It stores food

•It helps in protecting the internal tissue

•It helps in supporting the plant

*Collenchyma - The cells of collenchyma are elongated in shape. They are living and their corners are thickened. Each cell consists of cytoplasm, nucleus and a large central vacuole. It is found under the epidermis in the stem. It provides rigidity to the plants. It helps in providing elasticity to the parts of the plant.

*Sclerenchyma - It consists of fibres and sclereids. These cells are narrow and elongated and have tapering ends.The cell walls of these cells are thick due to the presence of lignin. These are mostly dead cells and they lack protoplasm. They occur in the veins of leaves and stems. They help in providing mechanical strength to the parts of the plant and protects the plant from extreme environmental conditions such as strong winds. The husk of coconut and fibres of cotton and jute are made up of schlerenchyma tissue. The shells of nuts are made up of sclereids.

What is Complex Permanent Tissue?

It is also known as vascular or conducting tissue. These tissues consist of more than one type of cell that work in co-ordination to perform certain functions.They help in transporting food and water throughout the plant. They consist of -

(a) Xylem - The water conducting tissue of the plant is known as xylem. It helps in transporting water and minerals from the root to the other parts of the plant. Xylem has four types of cells -

*Xylem Vessels - They are long and tube like and compose of a series of cells.

*Xylem Tracheids - They are also long and tube like and have tapering ends.

Both xylem vessels and xylem tracheids help to transfer water and minerals from the root to the other parts of the plant.

*Xylem Fibres - They give mechanical support to the parts of the plant.

*Xylem Parenchyma - The only living component of xylem is xylem parenchyma. It helps in the storage of food.It helps in the transportation of water and minerals.

(b) Phloem - The food conducting tissue of the plant is known as phloem. Material can move in both upward and downward direction in phloem.Phloem consists of sieve cells (living), phloem fibres (dead) , phloem parenchyma (living) and companion cells (living).

*Sieve Cells - These are elongated and have minute pores. Nucleus is absent at maturity. They help to transfer the food prepared by leaves to various parts of the plant.

*Phloem Fibres - They give mechanical strength to the plant. For example - textile fibres of flax and jute.

*Phloem Parenchyma Cells - They help in the storage of reserved food material.

*Companion Cells - Parenchyma cells that associate with the sieve cells and help in transporting water are known as companion cells.

Xylem and phloem are collectively known as the vascular bundle and form up the vascular system of the plant.

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