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Notes ⇒ Class 9th ⇒ Science ⇒ 6. Tissues

Notes 6. Tissues - Epidermis | Class 9 Science - Toppers Study

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6. Tissues

| Epidermis |

Notes 6. Tissues - Epidermis | Class 9 Science - Toppers Study


Epidermis:

The outer most layer of cells is called epidermis. The epidermis is usually made of a single layer of cells. The epidermis may thicker in plants of dry habitats.

Since, it has a protective role to play, cells of epidermal tissue form a continuous layer without intercellular spaces. Most epidermal cells are relatively flat. Often their outer and side walls are thicker than the inner wall.

Features:

(i) Epidermis may be thicker since protection against water loss is critical.

(ii) The entire surface of a plant has this outer covering of epidermis.

(iii) It protects all the parts of the plant.

(iv) Epidermal cells on the aerial parts of the plant often secrete a waxy, water-resistant layer on their outer surface.

(v) This aids in protection against loss of water, mechanical injury and invasion by parasitic fungi.

Functions Of Epidermis in plants:

(i) This aids in protection against loss of water,

(ii) Mechanical injury and invasion by parasitic fungi.

(iii) Its jelly like substances  forms a water resistant layer. 

Functions of Epidermis in roots:

Epidermal cells of the roots, whose function is water absorption, commonly bear
long hair-like parts that greatly increase the total absorptive surface area.

Role of Epidermis in Desert Plants:

Epidermis has a thick waxy coating of cutin (chemical substance with waterproof quality) on its outer surface.

Cutin: This is a chemical substance with waterproof quality, which is mainly found in epidermis of desert plants. 

Suberin: There is a chemical called suberin in the walls of outer protective
tissue (thick cork) or the bark of the tree that makes them impervious (harmless) to gases and water.

Stomata: There are many small pores in the epidermis (surface) of the leaf. These small pores are called stomata.

Protective Layer: As plants grow older, the outer protective tissue undergoes certain changes. A strip of secondary meristem replaces the epidermis of the stem. Cells on the outside are cut off from this layer. This forms the several-layer thick cork or the bark of the tree. Cells of cork are dead and compactly arranged without intercellular spaces

Functions of stomata:

(i) The process of transpiration takes place through stomata. 

(ii) The gaseous exchanges also take place through stomata.

Transpiration: This is a process of loss of water in the form of water vapour.

  • Stomata are enclosed by two kidney-shaped cells called guard cells.

Function of guard Cells:

They are necessary for exchanging gases with the atmosphere.

 

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Study Materials List:

Notes ⇒ Class 9th ⇒ Science
1. Matter in Our Surroundings
2. Is Matter around us Pure
3. Atoms and Molecules
4. Structure of The Atom
5. The Fundamental Unit of Life
6. Tissues
7. Diversity in Living Organisms
8. Motion
9. Force and Laws of Motion
10. Gravitation
11. Work and Energy
12. Sound
13. Why Do We Fall ill
14. Natural Resources
15. Improvement in Food Resources

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