84 BIOLOGY
C HAPTER 6
ANATOMY OF FLOWERING PLANTS
6.1 The Tissues You can very easily see the structural similarities and variations in the
external morphology of the larger living organism, both plants and
6.2 The Tissue
animals. Similarly, if we were to study the internal structure, one also
System
finds several similarities as well as differences. This chapter introduces
6.3 Anatomy of you to the internal structure and functional organisation of higher plants.
Dicotyledonous Study of internal structure of plants is called anatomy. Plants have cells
and as the basic unit, cells are organised into tissues and in turn the tissues
Monocotyledonous are organised into organs. Different organs in a plant show differences in
Plants their internal structure. Within angiosperms, the monocots and dicots
are also seen to be anatomically different. Internal structures also show
6.4 Secondary
adaptations to diverse environments.
Growth
6.1 THE TISSUES
A tissue is a group of cells having a common origin and usually performing
a common function. A plant is made up of different kinds of tissues. Tissues
are classified into two main groups, namely, meristematic and permanent
tissues based on whether the cells being formed are capable of dividing
or not.
6.1.1 Meristematic Tissues
Growth in plants is largely restricted to specialised regions of active cell division
called meristems (Gk. meristos: divided). Plants have different kinds of
meristems. The meristems which occur at the tips of roots and shoots and
produce primary tissues are called apical meristems (Figure 6.1).
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, ANATOMY OF FLOWERING PLANTS 85
Central cylinder
Cortex Leaf primordium
Protoderm Shoot apical
Meristematic zone
Initials of central
cylinder
Root apical Axillary bud
and cortex
meristem
Differentiating
Initials of
vascular tissue
root cap
Root cap
Figure 6.1 Apical meristem: (a) Root (b) Shoot
Root apical meristem occupies the tip of a root while the shoot apical
meristem occupies the distant most region of the stem axis. During the
formation of leaves and elongation of stem, some cells ‘left behind’ from
shoot apical meristem, constitute the axillary bud. Such buds are present
in the axils of leaves and are capable of forming a branch or a flower. The
meristem which occurs between mature tissues is known as intercalary
meristem. They occur in grasses and regenerate parts removed by the
grazing herbivores. Both apical meristems and intercalary meristems are
primary meristems because they appear early in life of a plant and
contribute to the formation of the primary plant body.
The meristem that occurs in the mature regions of roots and shoots of
many plants, particularly those that produce woody axis and appear
later than primary meristem is called the secondary or lateral meristem.
They are cylindrical meristems. Fascicular vascular cambium,
interfascicular cambium and cork-cambium are examples of lateral
meristems. These are responsible for producing the secondary tissues.
Following divisions of cells in both primary and as well as secondary
meristems, the newly formed cells become structurally and functionally
specialised and lose the ability to divide. Such cells are termed permanent
or mature cells and constitute the permanent tissues. During the
formation of the primary plant body, specific regions of the apical meristem
produce dermal tissues, ground tissues and vascular tissues.
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, 86 BIOLOGY
6.1.2 Permanent Tissues
The cells of the permanent tissues do not generally
divide further. Permanent tissues having all cells
similar in structure and function are called simple
tissues. Permanent tissues having many different
types of cells are called complex tissues.
Intercelluar space 6.1.2.1 Simple Tissues
A simple tissue is made of only one type of cells.
The various simple tissues in plants are
parenchyma, collenchyma and sclerenchyma
(Figure 6.2). Parenchyma forms the major
(a) component within organs. The cells of the
parenchyma are generally isodiametric. They
Thickened corners may be spherical, oval, round, polygonal or
Protoplasm
elongated in shape. Their walls are thin and made
Vacuole
up of cellulose. They may either be closely packed
Cell wall or have small intercellular spaces. The
parenchyma performs various functions like
photosynthesis, storage, secretion.
The collenchyma occurs in layers below the
epidermis in most of the dicotyledonous plants. It is
found either as a homogeneous layer or in patches.
(b) It consists of cells which are much thickened at the
corners due to a deposition of cellulose,
hemicellulose and pectin. Collenchymatous cells
may be oval, spherical or polygonal and often
Pits
Lumen contain chloroplasts. These cells assimilate food
Thick when they contain chloroplasts. Intercellular spaces
cell wall are absent. They provide mechanical support to the
Lumen
growing parts of the plant such as young stem and
Thick petiole of a leaf.
cell wall Sclerenchyma consists of long, narrow cells
A sclereid with thick and lignified cell walls having a few or
A fibre
numerous pits. They are usually dead and without
(c) protoplasts. On the basis of variation in form,
structure, origin and development, sclerenchyma
Figure 6.2 Simple tissues :
(a) Parenchyma may be either fibres or sclereids. The fibres are
(b) Collenchyma thick-walled, elongated and pointed cells,
(c) Sclerenchyma generally occuring in groups, in various parts of
the plant. The sclereids are spherical, oval or
cylindrical, highly thickened dead cells with very
2022-23
C HAPTER 6
ANATOMY OF FLOWERING PLANTS
6.1 The Tissues You can very easily see the structural similarities and variations in the
external morphology of the larger living organism, both plants and
6.2 The Tissue
animals. Similarly, if we were to study the internal structure, one also
System
finds several similarities as well as differences. This chapter introduces
6.3 Anatomy of you to the internal structure and functional organisation of higher plants.
Dicotyledonous Study of internal structure of plants is called anatomy. Plants have cells
and as the basic unit, cells are organised into tissues and in turn the tissues
Monocotyledonous are organised into organs. Different organs in a plant show differences in
Plants their internal structure. Within angiosperms, the monocots and dicots
are also seen to be anatomically different. Internal structures also show
6.4 Secondary
adaptations to diverse environments.
Growth
6.1 THE TISSUES
A tissue is a group of cells having a common origin and usually performing
a common function. A plant is made up of different kinds of tissues. Tissues
are classified into two main groups, namely, meristematic and permanent
tissues based on whether the cells being formed are capable of dividing
or not.
6.1.1 Meristematic Tissues
Growth in plants is largely restricted to specialised regions of active cell division
called meristems (Gk. meristos: divided). Plants have different kinds of
meristems. The meristems which occur at the tips of roots and shoots and
produce primary tissues are called apical meristems (Figure 6.1).
2022-23
, ANATOMY OF FLOWERING PLANTS 85
Central cylinder
Cortex Leaf primordium
Protoderm Shoot apical
Meristematic zone
Initials of central
cylinder
Root apical Axillary bud
and cortex
meristem
Differentiating
Initials of
vascular tissue
root cap
Root cap
Figure 6.1 Apical meristem: (a) Root (b) Shoot
Root apical meristem occupies the tip of a root while the shoot apical
meristem occupies the distant most region of the stem axis. During the
formation of leaves and elongation of stem, some cells ‘left behind’ from
shoot apical meristem, constitute the axillary bud. Such buds are present
in the axils of leaves and are capable of forming a branch or a flower. The
meristem which occurs between mature tissues is known as intercalary
meristem. They occur in grasses and regenerate parts removed by the
grazing herbivores. Both apical meristems and intercalary meristems are
primary meristems because they appear early in life of a plant and
contribute to the formation of the primary plant body.
The meristem that occurs in the mature regions of roots and shoots of
many plants, particularly those that produce woody axis and appear
later than primary meristem is called the secondary or lateral meristem.
They are cylindrical meristems. Fascicular vascular cambium,
interfascicular cambium and cork-cambium are examples of lateral
meristems. These are responsible for producing the secondary tissues.
Following divisions of cells in both primary and as well as secondary
meristems, the newly formed cells become structurally and functionally
specialised and lose the ability to divide. Such cells are termed permanent
or mature cells and constitute the permanent tissues. During the
formation of the primary plant body, specific regions of the apical meristem
produce dermal tissues, ground tissues and vascular tissues.
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, 86 BIOLOGY
6.1.2 Permanent Tissues
The cells of the permanent tissues do not generally
divide further. Permanent tissues having all cells
similar in structure and function are called simple
tissues. Permanent tissues having many different
types of cells are called complex tissues.
Intercelluar space 6.1.2.1 Simple Tissues
A simple tissue is made of only one type of cells.
The various simple tissues in plants are
parenchyma, collenchyma and sclerenchyma
(Figure 6.2). Parenchyma forms the major
(a) component within organs. The cells of the
parenchyma are generally isodiametric. They
Thickened corners may be spherical, oval, round, polygonal or
Protoplasm
elongated in shape. Their walls are thin and made
Vacuole
up of cellulose. They may either be closely packed
Cell wall or have small intercellular spaces. The
parenchyma performs various functions like
photosynthesis, storage, secretion.
The collenchyma occurs in layers below the
epidermis in most of the dicotyledonous plants. It is
found either as a homogeneous layer or in patches.
(b) It consists of cells which are much thickened at the
corners due to a deposition of cellulose,
hemicellulose and pectin. Collenchymatous cells
may be oval, spherical or polygonal and often
Pits
Lumen contain chloroplasts. These cells assimilate food
Thick when they contain chloroplasts. Intercellular spaces
cell wall are absent. They provide mechanical support to the
Lumen
growing parts of the plant such as young stem and
Thick petiole of a leaf.
cell wall Sclerenchyma consists of long, narrow cells
A sclereid with thick and lignified cell walls having a few or
A fibre
numerous pits. They are usually dead and without
(c) protoplasts. On the basis of variation in form,
structure, origin and development, sclerenchyma
Figure 6.2 Simple tissues :
(a) Parenchyma may be either fibres or sclereids. The fibres are
(b) Collenchyma thick-walled, elongated and pointed cells,
(c) Sclerenchyma generally occuring in groups, in various parts of
the plant. The sclereids are spherical, oval or
cylindrical, highly thickened dead cells with very
2022-23
