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Class 9, Science, Chapter-6, Lecture-2, Simple Permanent Tissues (Notes)

Parenchyma: 

Location: present in all the parts of plant 

Characteristics: 

  1. Cells have thin cell wall. 
  2. Consists of Living cells having nucleus 
  3. Vacuole is present in the cells. 
  4. Large intercellular spaces. 

Functions: 

  1. Provides support to plants. 
  2. Stores food, nutrients, water. 
  3. Chlorenchyma (Parenchyma containing Chlorophyll) performs photosynthesis. 
  4. Aerenchyma (Parenchyma containing air cavities) provides buoyancy to aquatic plants.

Collenchyma: 

Location: present below the epidermis in leaf stalks in plant 

Characteristics: 

  1. Cells have irregular cell wall thickened at corners. 
  2. Consists of Living cells having nucleus 
  3. Vacuole is present in the cells. 
  4. Small intercellular spaces. 

Functions: 

  1. Provides flexibility to plants. 
  2. Stores food, nutrients, water. 
  3. Performs photosynthesis. 
  4. Allows elongation of plants.

Differences Between:

Parenchyma

Collenchyma

Cells are round.

Cells are elongated.

Cells wall is thin.

Cells wall is unevenly thickened over the corners.

Provides turgidity to softer organs.

Provides mechanical strength as well as flexibility.

It forms the packing tissue of all plant organs.

It occurs hypodermally in dicot stems and leaves only.

Sclerenchyma: 

Location: present in stems, around vascular bundles, in the veins of leaves, in the covering of seeds, nuts and husk 

Characteristics: 

  1. Cells have thick cell wall made of LIGNIN. 
  2. Consists of dead cells. 
  3. Vacuole is absent in the cells. 
  4. No intercellular spaces. 

Functions: 

  1. Provides strength and hardness and stiffness to plants. 
  2. Protects seeds and nuts.

Differences Between:

Collenchyma

Sclerenchyma

It is living mechanical tissue.

It is dead mechanical tissue.

Wall thickening is uneven.

Wall thickening is uniform.

Wall thickening is of pectin and cellulose.

Wall thickening is of lignin.

Lumen or cell cavity is wide.

Lumen or cell cavity is narrow.

Collenchyma manufactures as well as stores food.

Sclerenchyma has no such function.

It keeps the organs soft.

It provides hardness.

Provides flexibility as well as strength.

Provides mechanical strength for facing various stresses.

Epidermis: 

Location: present in the entire outer surface of plants. 

Characteristics: 

  1. Made of a single layer of elongated and flat cells. 
  2. Outer wall is thicker than the inner wall. 
  3. Contains small pores called stomata for exchange of gases and transpiration. 
  4. No intercellular spaces. 

Functions: 

  1. Prevents loss of water. 
  2. Protects from injury. 
  3. Protects from parasitic invasion. 
  4. Stomata allow loss of excess water through transpiration. 
  5. Stomata allows exchange of gases.

Cork: 

Location: present in the outer surface of older parts of stems and roots of plants. 

Characteristics: 

  1. Multi layered. 
  2. Thick. 
  3. Consist of dead cells. 
  4. No intercellular spaces. 
  5. Presence of SUBERIN makes it impervious to gases and water. 

Functions: 

  1. Protects from injury. 
  2. Protects from parasitic invasion. 
  3. Makes the outer cover impervious to gases and water.