Plant Anatomy
It is a branch of biology, which deals with the study of internal structure of the body by a section
cutting technique.
Concept of Tissues
(Term tissue was given by N. Grew (1682), (therefore, he is regarded as "Father of plant
anatomy) and Nageli (1858) is regarded as "father of modern anatomy". In simple terms, tissue
can be definedas a groups or a mass of structurally similar or dissimilar cells that perform or help
to perform acommon function and have a common origin is called a tissue". The study of tissue
is called histology and study of disease related to tissue is known as histopathology. The standard
tool for studying tissues is by sectioning the different plant parts.
Depending upon the dividing capacity, the tissues are classified into two types:
1. Meristematic
2. Permanent
Meristematic Tissue
The term meristem is derived from a Greek word meristos which means divisible. Thus,
the meristematic tissue can be defined as a group of immature cells which has the capacity of
division. The meristem tissues are characterised by the following features:
They are small, thin-walled and living cells. The thin cell wall is elastic and cellulosic.
Secondary wall is usually absent. The cells are compactly arranged and lack intercellular spaces.
They are usually isodiametric, spherical, oval or polygonal in shape. Each cell contains dense
cytoplasm with a large, distinct and prominent nucleus. Vacuoles are either absent or very small.
Plastids are present in the form of proplastids. In fact, meristematic cells are parent cells from
which all other new cells are added to the plant body.
Classification of Meristems
1. Classification Based on Origin and Development: Based on origin and development, the
meristems are classified into two types:
a) Promeristem: It is called primordial meristem or embryonic meristem which originates
from embryo. It is present where an organ or a part of plant is initiated e.g. germinating
embryos or young seedlings. Promeristem is found at the apices of shoots and roots. It
gives rise to primary meristem.
b) Primary meristem: It is a type of meristem which originates from the promeristem and
is responsible for the primary growth. It is also always in the state of division. It gives
rise to primary permanent tissue. It is found below the promeristem of apices.
c) Secondary meristem: They develop from permanent tissue by differentiation in later
stage of growth. It gives rise to secondary permanent tissues. Central vacuole is also
present. Secondary meristem increases the diameter of plant. Inter fascicular cambium,
cork cambium and vascular cambium of root are the examples of secondary meristem. It
also helps in wound healing process in plants.
, 2. Classification Based on Position: Based on the position in the plant body, the
meristems are classified into three types-apical, intercalary and lateral.
a) Apical Meristems: The meristems located at the apices or the growing points of
main and lateral shoots and roots are called apical meristems. They include both
promeristems and primary meristems. The apical meristems increase the length
of the plant body. They divide and gradually attain the shape of permanent
tissues.
b) Intercalary Meristems: The meristem present between the regions of
permanent tissues is called intercalary meristem. It is considered to be a part of
the apical meristem which gets separated from the apex due to the formation of
intermediate permanent tissues. Intercalary meristems are found at the base of
leaves in Pinus, at the base of internode in grasses and Equisetum and below the
node in Mentha.
c) Lateral
Meristems: Lateral
meristems lie along
the lateral sides of
roots and stems.
They are
responsible for the
increase in
thickness of the
plant part. Vascular
cambium and cork
cambium are
common examples
of lateral
meristems. The
vascular cambium is the primary meristem and cork cambium is the secondary
meristem. Both of them divide to form secondary permanent tissues during
secondary growth in a dicot plant.
3. Classification Based on Function: On the basis of function, Haberlandt (1914)
classified meristems into three categories:
a) Protoderm: This is the outermost layer of meristem which divides periclinally
and forms the outer epidermal layer.
b) Procambium: It is located inside the protoderm. It consists of narrow, elongated
meristematic cells that differentiate into the primary vascular tissues.
c) Ground Meristem: It constitutes the major part of the apical meristem. It
consists of large thin-walled cells that differentiate into ground tissue system, i.e.
It is a branch of biology, which deals with the study of internal structure of the body by a section
cutting technique.
Concept of Tissues
(Term tissue was given by N. Grew (1682), (therefore, he is regarded as "Father of plant
anatomy) and Nageli (1858) is regarded as "father of modern anatomy". In simple terms, tissue
can be definedas a groups or a mass of structurally similar or dissimilar cells that perform or help
to perform acommon function and have a common origin is called a tissue". The study of tissue
is called histology and study of disease related to tissue is known as histopathology. The standard
tool for studying tissues is by sectioning the different plant parts.
Depending upon the dividing capacity, the tissues are classified into two types:
1. Meristematic
2. Permanent
Meristematic Tissue
The term meristem is derived from a Greek word meristos which means divisible. Thus,
the meristematic tissue can be defined as a group of immature cells which has the capacity of
division. The meristem tissues are characterised by the following features:
They are small, thin-walled and living cells. The thin cell wall is elastic and cellulosic.
Secondary wall is usually absent. The cells are compactly arranged and lack intercellular spaces.
They are usually isodiametric, spherical, oval or polygonal in shape. Each cell contains dense
cytoplasm with a large, distinct and prominent nucleus. Vacuoles are either absent or very small.
Plastids are present in the form of proplastids. In fact, meristematic cells are parent cells from
which all other new cells are added to the plant body.
Classification of Meristems
1. Classification Based on Origin and Development: Based on origin and development, the
meristems are classified into two types:
a) Promeristem: It is called primordial meristem or embryonic meristem which originates
from embryo. It is present where an organ or a part of plant is initiated e.g. germinating
embryos or young seedlings. Promeristem is found at the apices of shoots and roots. It
gives rise to primary meristem.
b) Primary meristem: It is a type of meristem which originates from the promeristem and
is responsible for the primary growth. It is also always in the state of division. It gives
rise to primary permanent tissue. It is found below the promeristem of apices.
c) Secondary meristem: They develop from permanent tissue by differentiation in later
stage of growth. It gives rise to secondary permanent tissues. Central vacuole is also
present. Secondary meristem increases the diameter of plant. Inter fascicular cambium,
cork cambium and vascular cambium of root are the examples of secondary meristem. It
also helps in wound healing process in plants.
, 2. Classification Based on Position: Based on the position in the plant body, the
meristems are classified into three types-apical, intercalary and lateral.
a) Apical Meristems: The meristems located at the apices or the growing points of
main and lateral shoots and roots are called apical meristems. They include both
promeristems and primary meristems. The apical meristems increase the length
of the plant body. They divide and gradually attain the shape of permanent
tissues.
b) Intercalary Meristems: The meristem present between the regions of
permanent tissues is called intercalary meristem. It is considered to be a part of
the apical meristem which gets separated from the apex due to the formation of
intermediate permanent tissues. Intercalary meristems are found at the base of
leaves in Pinus, at the base of internode in grasses and Equisetum and below the
node in Mentha.
c) Lateral
Meristems: Lateral
meristems lie along
the lateral sides of
roots and stems.
They are
responsible for the
increase in
thickness of the
plant part. Vascular
cambium and cork
cambium are
common examples
of lateral
meristems. The
vascular cambium is the primary meristem and cork cambium is the secondary
meristem. Both of them divide to form secondary permanent tissues during
secondary growth in a dicot plant.
3. Classification Based on Function: On the basis of function, Haberlandt (1914)
classified meristems into three categories:
a) Protoderm: This is the outermost layer of meristem which divides periclinally
and forms the outer epidermal layer.
b) Procambium: It is located inside the protoderm. It consists of narrow, elongated
meristematic cells that differentiate into the primary vascular tissues.
c) Ground Meristem: It constitutes the major part of the apical meristem. It
consists of large thin-walled cells that differentiate into ground tissue system, i.e.
