Meristems and Its Classification Basic concept of meristem For B.S level For presentation

1. Meristematic Tissues
 Introduction of Meristematic
Tissue
 Structure of Meristematic Cells
 Classification of Meristems:
1. On the Base of Position
2. On the Base of Function
3. On the Base of Origin and
Development
4. On the Base of Growth Pattern
and Planes of Division
(KASHIF RAZA)

2. Meristematic Tissues
The term Meristem is derived from a
Greek word Meristos=Divisible
It is a tissue composed of immature not
well differentiated cells which has the
capacity of division is called
meristematic tissue.
It is also called Formative tissues.
Loaction:
The apices of roots, shoots and
their lateral branches have meristem at
their tips.
It increases length of respective axis.

3. Structure of Meristematic Cell
 The cells in the meristem are thin walled.
 Meristematic cells are spherical, polygonal, oval
and isodiametric in shape.
 Rich in protoplast without reserve material.
 The vacuoles are small and are scattered
throughout the protoplast.
 Thick walled meristematic cells are found in the
apical meristems.
Types:
1. Initiating cells :These cells retain the
meristematic activity throughout the growth of
the plant.
2. Derivative cells :These cells derive from meristem
into various tissue element
3. Differentiation cells :The derivatives undergo
morho-physiology changes and this process is
called differentiation.

4. Classification of Meristems
On The Base Of Position Of Meristem:
1. Apical meristem:
The meristems present at the tip of roots and shoot are called
apical meristems.
 They play important role in primary growth.
2. Intercalary meristem:
The meristem situated at the bases of internodes is called
intercalary meristem.
 They important role in the in the production of leaves and
flower.
3. Lateral meristem:
The longitudinal axis of dividing cells present in the vascular
and cork tissue of the plants are called lateral meristem.
 They play an important role in the diameter of stem and
root.
 They are involved in secondary growth.

5. On The Base Of Origin and Development of Meristem
1. Primary Meristem:
The meristem developing from directly from the
embryonic cells are called primary meristem.
 Fundamental body parts are developed such as
epidermis ,cortex and mesophyll and primary
vascular tissues.
b. Secondary Meristems:
The meristem developed from differentiated and
mature tissue by resuming the meristematic activity is
called secondary meristem.
 Secondary vascular tissue and protective tissue
develop from secondary meristem.
 Its example are phellogen and cork cambium.
Terms:
Meristematic cells layer that are responsible for the
development of the periderm is called phellogen.
 Cells that grow inwards from there are termed
Phelloderm.
 Cells that develop outward are termed Phellem.

6. On the Basis of Function
a. Protoderm:
It is the outer layer of meristem
which will become epidermal
meristem.
b. Procambium:
This is responsible for the
development of the primary
vascular which will become the
vascular tissue.
c. Ground meristem:
Which will form the ground
tissue.(parenchyma,collenchyma,scl
erenchyma tissue).

7. On The Basis of Growth Pattern and Planes of Division
a) Mass Meristem:
A meristem in which cell division in all planes results in
increase in mass.
 For example: growth resulting in the formation of
endosperm and takes place in young embryos of some
plant.
b) Rib Meristem:
A meristem in which cell division occur anticlinal (t right
angles to the longitudinal axis) in one plane and give rise
to vertical rows and column.
 This type of growth occurs during the development of
cortex of root and pith and the cortex of stem.
c) Plate Meristem:
A meristem in which cell divides by anticlinal divisions
with the result that number of layers do not increase and
a platelike structure formed.
 Growth shown by flat blades of angiosperm leaves.