A tissue is defined as group of similar or

dissimilar cells which perform or help to

perform a particular functions and have a

common origin.

Plants, like all organisms, are made up of innumerable cells of different varieties.

These cells are organized into tissues based on their specific functions.

Plants tissue are classified into two

groups : -

PERMANENT TISSUE MERISTEMATIC

TISSUE

DIFFERENTIATEDED CELLS

UNDIFFERENTIATEDED CELLS

PERMANENT TISSUE

The tissue which is composed

of mature and differentiated cell that has

already undergone definite growth and has

assume definite size, shape and function is

known as permanent tissue.

PERMANENT TISSUE ARE OF TWO

TYPES :-

Simple permanent tissues

Complex permanent tissues

Simple permanent tissues

Simple permanent tissue is the collection of similar

cells performing similar function. It is further divided

into three different types on the nature of cell:

1.PARENCHYMA

2.COLLENCHYMA

3.SCLERENCHYMA

PARENCHYMA

The most common type of simple permanent tissue present in all the plants

which are isodiametric i.e. expanded equally and vary greatly in morphology

along with physiology is known as parenchyma.

It is composed of thin wall living cell and cell wall is made of cellulose. Intercellular

space is present and cytoplasm is vacuolated. n transverse section, parenchyma cell

appear circular,oval,rectangular or polygonal in shape. Parenchyma tissue present in

almost all plant organs specially in non woody region. It forms the bulk of ground tissue

in all plant organs.

When parenchyma cell contain chlorophyll, they are said

chlorenchyma.Chlorenchyma present in cortex of leaf is said mesophyll tissue

which is further differentiated into pallisade and spongy.

The parenchyma cells in the cortex of aquatic plant encloses large air spaces

and cavities called arenchyma.

a)The main function of parenchyma cell is to store food material.

b)The chlorenchyma cells take part in photosynthesis.

c)The aerenchyma helps plant to remain floating on surface of

water by providing buoyancy.

d)The parenchyma cell in the epidermis perform protective

function.

e)During secondary growth parenchyma cell acquire the power

of division and become secondary meristem which by producing

secondary permanent tissue help in the increase of diameter of

plant.

FUNCTION

COLLENCHYMA

The mechanical tissue present in the plant body especially in the primary body

of dicot stem below the epidermis forming the hypodermis is called

collencyma.The cells are elongated with oblique ,slightly rounded with tapering

ends. It is composed of living and thick walled cells. The cells are thickened at

the corner against the intercellular spaces. The thickening is due to deposition

of cellulose,hemicellulose or pectin.

In transverse section they appear circular, oval or polygonal. In secondary body

of dicot stem and in monocot stem collenchymas is absent. In roots also rarely

present.Collenchyma stem may be present in petiole of dicot stem.

a)Due to its peculiar thickening it provides mechanical

strength and elasticity to the growing organs.

b)As collenchymas cells are capable of elongation, they help

in elongation of organ along with the mechanical strength.

c)Chlorenchyma cells containing chloroplast helps in

photosynthesis and also mechanical strength.

FUNCTION

SCLERENCHYMA

The chief mechanical tissue of the plant body composed of

highly thick walled cell with little or no protoplasm is called

sclerenchyma.The thickening of cell wall is due to deposition of

cellulose or lignin or both. Lignin deposited cells are said

lignified. The sclerenchyma cells are broadly classified into two

types:

i) FIBRES

ii) SCLERIDS

FIBRES

Fibres cells are long,narrow,thick walled spindle shape with

tapering ends. As they look fibre like in longitudinal section, the

name is fibre. The fibre cells are without intercellular spaces. They

are dead and empty. In Transverse section fibre cell appear

hexagonal. The cell walls are mostly lignified. It is present in

different regions in most of the plants. It commonly occurs in

hypodermis of monocot stem as bundle sheath around vascular

bundle, around pericycle and also under xylem(wood fibre)and

phloem(bast fibre).It's principal function is to give mechanical

support to plant body. The fibre cell present in xylem and phloem

also help i the conductive of water and mineral salt along with

food.

SCLERIDS

These are highly thick walled, dead sclerenchyma

cells which are developed in different parts of plant

body in order to meet the local mechanical need.

They are present in the epidermis, cortex as well as

tip. The hard covering of stony fruit is sclerids.Sclerids

may occur singly or in groups. On the basis of their

structure, there are different sclerids as macro

sclerids,osteo sclerids and brachy sclerids.