Class 9, Science, Chapter-6, Lecture-2, Simple Permanent Tissues (Notes)
Parenchyma:
Location: present in all the parts of plant
Characteristics:
- Cells have thin cell wall.
- Consists of Living cells having nucleus
- Vacuole is present in the cells.
- Large intercellular spaces.
Functions:
- Provides support to plants.
- Stores food, nutrients, water.
- Chlorenchyma (Parenchyma containing Chlorophyll) performs photosynthesis.
- Aerenchyma (Parenchyma containing air cavities) provides buoyancy to aquatic plants.
Collenchyma:
Location: present below the epidermis in leaf stalks in plant
Characteristics:
- Cells have irregular cell wall thickened at corners.
- Consists of Living cells having nucleus
- Vacuole is present in the cells.
- Small intercellular spaces.
Functions:
- Provides flexibility to plants.
- Stores food, nutrients, water.
- Performs photosynthesis.
- 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:
- Cells have thick cell wall made of LIGNIN.
- Consists of dead cells.
- Vacuole is absent in the cells.
- No intercellular spaces.
Functions:
- Provides strength and hardness and stiffness to plants.
- 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:
- Made of a single layer of elongated and flat cells.
- Outer wall is thicker than the inner wall.
- Contains small pores called stomata for exchange of gases and transpiration.
- No intercellular spaces.
Functions:
- Prevents loss of water.
- Protects from injury.
- Protects from parasitic invasion.
- Stomata allow loss of excess water through transpiration.
- Stomata allows exchange of gases.
Cork:
Location: present in the outer surface of older parts of stems and roots of plants.
Characteristics:
- Multi layered.
- Thick.
- Consist of dead cells.
- No intercellular spaces.
- Presence of SUBERIN makes it impervious to gases and water.
Functions:
- Protects from injury.
- Protects from parasitic invasion.
- Makes the outer cover impervious to gases and water.