Class notes Class 9

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TISSUES
In unicellular organisms all the life processes such as digestion, respiration, excretion, reproduction etc are performed by
the single cell.

But in multicellualr organisms different groups of cells perform different functions. Thus there is division of
labour in the cell and each tissue is composed of cells that originate from common parent cells and have a characteristic
shape, size and arrangement.

TISSUE: A group of cells that are similar in structure and work together to achieve a particular function forms a tissue.
Importance of tissue:

1. Formation of tissues has brought about division of labour in multicellular organisms.
2. Tissues become organized to form organs and organs into organ system.
3. Workload of individual cell has been decreased.
4. Due to improved organization and higher efficiency, multicellular organisms have higher survival.

TYPES OF TISSUES:
Tissue



Plant Tissue Animal Tissue




Plant Tissue



Meristematic Tissue Permanent Tissue



Apical Latera Intercalary Simple Complex/Compound
l (Protective & Supporting) (Conducting Tissue)




Parenchym Collenchyma Sclerenchyma Phloem Xylem
a

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MERISTEMATIC TISSUE:
 It consists of undifferentiated, actively dividing cells i.e. helps in growth of the plant and
 Found in those regions of the plants that grow. e.g. - root tip, shoot tip & cambium.
 These tissues are living and bring about an increase in the length and girth (thickness) of the plant.


Characteristics of Meristematic tissue:

1. The cells are in active stage of cell division.
2. Each Meristematic cells contains dense or abundant cytoplasm and a single large nucleus.
3. The Meristematic cells are compactly arranged i.e. without intercellular space between them.
4. Cell wall is made of thin cellular layer.
5. Cells may be spherical, oval, polygonal or rectangular in shape.
6. Cells may or may not contain vacuoles.

Function:

1. It have the ability to divide, hence they continuously divide to produce new cells which keep differentiating to
form specialized cells of the plant.
2. The cells of the root tip and shoot tip bring about an increase in length of the plant.
3. The cells in the lateral region i.e. cambium bring about an increase in the girth (thickness) of the plant.

Types of Meristematic tissue:

(A) Apical meristem:
 Present at the apex of root or stem.
 Responsible for increase in length of an
axis.
(B) Lateral meristem / Cambium:
 They lie on the lateral side of stem and
root
 Help in increasing the thickness (girth)
of the stem & root.
(C) Intercalary meristem:
 They lie at the base of the leaves or
internodes on twigs.
 Help in longitudinal growth of plants i.e.
responsible for increase in length of
intermodal region.
PERMANENT TISSUE:
 These tissues originate from the Meristematic tissues.
 Different types of permanent tissues are formed by the differentiation of cells of the Meristematic tissue.
Cell differentiation: the process of taking up a permanent shape, size & function is called differentiation.

Characteristics:
1. Cells have lost the power of division i.e. they donot divide.
2. They have a definite form and size.
3. They are differentiated cells and carry out specific function.
4. They may be living or dead cells.
5. They may have thin / thick cell wall.
6. The cells are large with vacuolated cytoplasm.