A group or collection of similar cells performing or help to perform same function and arise from the same origin are called tissues.

The tissues are of different types depending on the functions of the organism, they are mainly of two categories PLANT TISSUES and ANIMAL TISSUES.

• ◎The cells are made of thin & elastic cell wall made of cellulose.

• ◎The cells may be round , oval, polygonal or rectangular in shape.

• ◎They are compact, having no intercellular space.

• ◎There is a large nucleus and abundant cytoplasm.

• ◎The protoplasm contains very few or no vacuoles at all.

Plants perform functions which are different from animals and also their structure is different , hence they have tissues which are different from animals. They are further classified into many sub categories which is shown in the table below:

• These tissues arise from the meristematic tissue.

• The cells of this tissue gradually loose their power to divide and acquire a definite shape, size and function.

• These tissues may be living or dead.

• There are 2 types of permanent tissues

1. Simple permanent tissue

2. Complex permanent tissue.

• This tissue comprises of same type of cells which perform the same function and all arise from the same origin.

• There are three categories of simple permanent tissues:

• Parenchyma

• Collenchyma

• Sclerenchyma.

• Characteristics:

a) The cells are living.

b) The cells are thin walled.

c) There may or may not be intercellular spaces.

d) They are the most unspecialized cells.

e) No depositions are seen, the cell wall consists only of cellulose.

f) There is a prominent nucleus, cytoplasm & vacuoles.

• There are some special types of parenchyma tissues :

• Storage parenchyma : The cells enlarge to store nutrients & water.

• Aerenchyma : Air cavities are present in the parenchyma tissue to provide buoyancy to the aquatic plants.

• Chlorenchyma : These parenchyma cells have presence of chlorophyll & hence can perform the function of photosynthesis.

Parenchyma tissue is found generally in all parts of the plant body. It forms the Ground tissue in leaves, stem, roots & fruits etc.

a) To store materials such as starch, proteins, hormones etc and waste products such as gum, tannin, resin etc.

b) Parenchyma cells perform the metabolic activities of the plant.

c) Forms the packaging tissue between the specialized tissue.

d) By providing turgidity , they provide mechanical strength.

e) Chlorenchyma helps in performing photosynthesis.

• The major difference is that the cells of meristematic tissue divide repeatedly while the cells of permanent tissue have no such ability.• The cells of permanent tissue are derived from the meristematic tissue.• Permanent tissue is made up with differentiated cells from the meristematic cell, but the cells of meristematic tissues remain undifferentiated.• The cells of meristematic tissue are small and have a similar structure with thin cell.