Notes for class 7

Location of permanent tissue in the plants :- The permanent tissue is present in all parts of plant except meristematic zone.

Permanent tissues are of two types :-

1. Simple permanent tissue :- Simple permanent tissue is called simple because it is made up of only one kind of cells. All the cells of this type of tissue are identical in structure and function. For example :- Epidermis, Cork, Parenchyma, Collenchyma, Sclerenchyma etc.
2. Complex permanent tissue :- In complex permanent tissue more than one kind of cells are present which perform a specific function. For example :- Xylem and Phloem.

Protective simple permanent tissue :-

Epidermis :- 

• Epidermis is present as external protective cover over all parts of plant.
• The epidermis is made up of living cells.
• Epidermis is present as single layer.
• Ex. - Epidermis of leaves secrete a waxy substance called cuticle.

Cork :- 

• Cork is simple permanent tissue which is protective in function.
• Cells of cork are dead.
• Cork is found in woody dicot stem.

 Supportive simple permanent tissue :-

Parenchyma tissue :-

• Cells of parenchyma tissue are living.
• Cell wall is thin and large vacuole is present in the center of cell for storage of materials.
• Cells are oval or polygonal in shape and nucleus ,cytoplasm shifts towards periphery.
• Parenchyma tissue stores food material and help in cell to cell conduction of water in the plant.

Note :- The parenchyma tissue having chloroplast in it, is called Clorenchyma  . The chlorenchyma tissue is involve in photosynthesis. It is found in the leaves.

Collenchyma tissue :-

• Cells of collenchyma is living but its shape is elongated.
• Collenchymatous cells are thick at the corners due to deposition of materials.
• Main function of collenchyma tissue is to provide the mechanical strength and flexibility to aerial parts of plants.