permanent tissue - simple tissue - parenchyma , collenchyma , sclerenchyma.

Permanent tissues

 This include Parenchyma, collenchyma , sclerenchyma

We have elaborated ground tissues here

I)Parenchyma –

Distinguishing features-

1)They have power of division whenever is necessary.

2)They are living cells.

3) They are thin walled they have primary and secondary walls of cellulose and hemicellulose.

4)This cells are isodimetric (having same size)

5) They are of variable shape like  oval , polygonal, hexagonal.

6)They have intercellular spaces.

They are of two types

a)chlorenchyma- Parenchyma cells which have chlorophyll pigment in them known as chlorenchyma.

b)aerenchyma – parenchyma cells have air spaces known  as aerenchyma.

c)prosenchyma- present in pricycle, long and tapering cells.

Where are they present?

1)Cortex of root and stem

2)mesophyll of cells (palisade tissue and spongy parenchyma)

Function-

1)They are storage cells.

2)Photosynthesis.

3) gives buyoancy  and helps in floating on water

4) They can act as secretory cells.

Collenchyma-

Characters of collenchyma cells –

1) They are present in shape oval , rounded, hexagonal, polygonal.

2)There is deposition of pectin along with cellulose and hemicellulose towards the edges and corner .

3) Due to pectin they lack intercellular spaces.

4)They are living cells.

5)They will do not divides furtherly.

Where are they present?

1)Base of the petiole

2)Hypodermis of dicot stem

Function

1)They provide mechanical strength .

2)They provide flexibility .Due to which flower and fruit do not fall.(fruit fall after maturation  because the absissic layer is formed.

3)They may perform photosynthesis.

Sclerenchyma-

Distinguishing features of sclerenchyma-

1)They are dead at maturity.

2)They have deposition of lignin, lignin is impermeable to water and gaseous so the cells does not get nourishment , due to that cell dies.

3)They have lumen which is central part within the cell wall

Scelerenchyma divided furtherly-

i)Fibres- They are long and spindle like

their distribution on basis of location

a)Present in phloem –phloem fibre or bast fibre

b)Present in xylem- xylem fibres.

c)present in husk of coconut