Notes of class 7

Sclerenchyma tissue :- 

• Sclerenchyma is made up of dead cellls.
• Cells of sclerenchyma become dead due to excess deposition of material around the cells.
• Sclerenchyma cells provide mechanical strength to the plant parts.

Complex permanent tissue :- The complex permanent tissue is represented by conducting tissue xylem and phloem. Xylem is responsible for transportation of water and minerals in the plant and phloem is responsible for translocation of prepared food from the leaf to all parts of plants.

Xylem :- 

• Xylem is made up of four types of cells - (i) Xylem tracheids (ii) Xylem vessels (iii) Xylem fibres (iv) Xylem Parenchyma.
• Cells of xylem are thick walled, tubular.
• All cells of xylem are dead except xylem parenchyma.
• Xylem vessels are long tubular cells joint end to end and form a long tubular pipe for transportation of water and mineral in the plant.
• Xylem tracheids are responsible for transverse transportation of water and mineral.
• Xylem fibres are helpful in joining all other cells of xylem tissue together.

   Phloem :- 

• Phloem is made up of four types of cells - (i) Sieve tubes (ii) Companion cells (iii) Phloem Parenchyma (iv) Phloem fibres.
• All cells of phloem are living except phloem fibres.
• Sieve tubes joint end to end and form a long tube through which soluble food move from leaves to other parts of plants.
• At the junction of sieve tube perforated ( with small holes ) cell wall is present which make the sieve plates. It slow down gravitational movement of soluble food.
• Phloem parenchyma cells store the food.
• Phloem fibres join other components (cell ) of phloem tissue.