NCERT Textbook Chapter 6 - Tissues, Science, Class 9 Class 9 Notes | EduRev

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Class 9 : NCERT Textbook Chapter 6 - Tissues, Science, Class 9 Class 9 Notes | EduRev

 Page 1


From the last chapter, we recall that all living
organisms are made of cells. In unicellular
organisms, a single cell performs all basic
functions. For example, in Amoeba, a single
cell carries out movement, intake of food and
respiratory gases, respiration and excretion.
But in multi-cellular organisms there are
millions of cells. Most of these cells are
specialised to carry out a few functions. Each
specialised function is taken up by a different
group of cells. Since these cells carry out only
a particular function, they do it very
efficiently. In human beings, muscle cells
contract and relax to cause movement, nerve
cells carry messages, blood flows to transport
oxygen, food, hormones and waste material
and so on. In plants, vascular tissues conduct
food and water from one part of the plant to
other parts. So, multi-cellular organisms
show division of labour. Cells specialising in
one function are often grouped together in
the body. This means that a particular
function is carried out by a cluster of cells at
a definite place in the body. This cluster of
cells, called a tissue, is arranged and designed
so as to give the highest possible efficiency of
function. Blood, phloem and muscle are all
examples of tissues.
A group of cells that are similar in
structure and/or work together to achieve a
particular function forms a tissue.
6.1 Are Plants and Animals Made
of Same Types of Tissues?
Let us compare their structure and functions.
Do plants and animals have the same
structure? Do they both perform similar
functions?
There are noticeable differences between
the two. Plants are stationary or fixed – they
don’t move. Most of the tissues they have are
supportive, which provides them with
structural strength. Most of these tissues are
dead, since dead cells can provide mechanical
strength as easily as live ones, and need less
maintenance.
Animals on the other hand move around
in search of food, mates and shelter. They
consume more energy as compared to plants.
Most of the tissues they contain are living.
Another difference between animals and
plants is in the pattern of growth. The growth
in plants is limited to certain regions, while
this is not so in animals. There are some
tissues in plants that divide throughout their
life. These tissues are localised in certain
regions. Based on the dividing capacity of the
tissues, various plant tissues can be classified
as growing or meristematic tissue and
permanent tissue. Cell growth in animals is
more uniform. So, there is no such
demarcation of dividing and non-dividing
regions in animals.
The structural organisation of organs and
organ systems is far more specialised and
localised in complex animals than even in very
complex plants. This fundamental difference
reflects the different modes of life pursued
by these two major groups of organisms,
particularly in their different feeding methods.
Also, they are differently adapted for a
sedentary existence on one hand (plants) and
active locomotion on the other (animals),
contributing to this difference in organ system
design.
It is with reference to these complex
animal and plant bodies that we will now talk
about the concept of tissues in some detail.
6 6
6 6 6
T T T T TISSUES ISSUES ISSUES ISSUES ISSUES
Chapter
Page 2


From the last chapter, we recall that all living
organisms are made of cells. In unicellular
organisms, a single cell performs all basic
functions. For example, in Amoeba, a single
cell carries out movement, intake of food and
respiratory gases, respiration and excretion.
But in multi-cellular organisms there are
millions of cells. Most of these cells are
specialised to carry out a few functions. Each
specialised function is taken up by a different
group of cells. Since these cells carry out only
a particular function, they do it very
efficiently. In human beings, muscle cells
contract and relax to cause movement, nerve
cells carry messages, blood flows to transport
oxygen, food, hormones and waste material
and so on. In plants, vascular tissues conduct
food and water from one part of the plant to
other parts. So, multi-cellular organisms
show division of labour. Cells specialising in
one function are often grouped together in
the body. This means that a particular
function is carried out by a cluster of cells at
a definite place in the body. This cluster of
cells, called a tissue, is arranged and designed
so as to give the highest possible efficiency of
function. Blood, phloem and muscle are all
examples of tissues.
A group of cells that are similar in
structure and/or work together to achieve a
particular function forms a tissue.
6.1 Are Plants and Animals Made
of Same Types of Tissues?
Let us compare their structure and functions.
Do plants and animals have the same
structure? Do they both perform similar
functions?
There are noticeable differences between
the two. Plants are stationary or fixed – they
don’t move. Most of the tissues they have are
supportive, which provides them with
structural strength. Most of these tissues are
dead, since dead cells can provide mechanical
strength as easily as live ones, and need less
maintenance.
Animals on the other hand move around
in search of food, mates and shelter. They
consume more energy as compared to plants.
Most of the tissues they contain are living.
Another difference between animals and
plants is in the pattern of growth. The growth
in plants is limited to certain regions, while
this is not so in animals. There are some
tissues in plants that divide throughout their
life. These tissues are localised in certain
regions. Based on the dividing capacity of the
tissues, various plant tissues can be classified
as growing or meristematic tissue and
permanent tissue. Cell growth in animals is
more uniform. So, there is no such
demarcation of dividing and non-dividing
regions in animals.
The structural organisation of organs and
organ systems is far more specialised and
localised in complex animals than even in very
complex plants. This fundamental difference
reflects the different modes of life pursued
by these two major groups of organisms,
particularly in their different feeding methods.
Also, they are differently adapted for a
sedentary existence on one hand (plants) and
active locomotion on the other (animals),
contributing to this difference in organ system
design.
It is with reference to these complex
animal and plant bodies that we will now talk
about the concept of tissues in some detail.
6 6
6 6 6
T T T T TISSUES ISSUES ISSUES ISSUES ISSUES
Chapter
uestions
1. What is a tissue?
2. What is the utility of tissues in
multi-cellular organisms?
6.2 Plant Tissues
6.2.1 MERISTEMATIC TISSUE
? From the above observations, answer
the following questions:
1. Which of the two onions has longer
roots? Why?
2. Do the roots continue growing even
after we have removed their tips?
3. Why would the tips stop growing in
jar 2 after we cut them?
The growth of plants occurs only in certain
specific regions. This is because the dividing
tissue, also known as meristematic tissue, is
located only at these points. Depending on
the region where they are present,
meristematic tissues are classified as apical,
lateral and intercalary (Fig. 6.2). New cells
produced by meristem are initially like those
of meristem itself, but as they grow and
mature, their characteristics slowly change
and they become differentiated as
components of other tissues.
Fig. 6.1: Growth of roots in onion bulbs
Activity ______________6.1
? Take two glass jars and fill them with
water.
? Now, take two onion bulbs and place
one on each jar, as shown in
Fig. 6.1.
? Observe the growth of roots in both the
bulbs for a few days.
? Measure the length of roots on day 1,
2 and 3.
? On day 4, cut the root tips of the onion
bulb in jar 2 by about 1 cm. After this,
observe the growth of roots in both the
jars and measure their lengths each
day for five more days and record the
observations in tables, like the table
below:
Length Day 1 Day 2 Day 3 Day 4 Day 5
Jar 1
Jar 2
Q
Apical meristem is present at the growing
tips of stems and roots and increases the
length of the stem and the root. The girth of
the stem or root increases due to lateral
meristem (cambium). Intercalary meristem is
the meristem at the base of the leaves or
internodes (on either side of the node)
on twigs.
Apical meristem
Intercalary meristem
Lateral meristem
Fig. 6.2: Location of meristematic tissue in plant body
Jar 1 Jar 2
TISSUES 69
Page 3


From the last chapter, we recall that all living
organisms are made of cells. In unicellular
organisms, a single cell performs all basic
functions. For example, in Amoeba, a single
cell carries out movement, intake of food and
respiratory gases, respiration and excretion.
But in multi-cellular organisms there are
millions of cells. Most of these cells are
specialised to carry out a few functions. Each
specialised function is taken up by a different
group of cells. Since these cells carry out only
a particular function, they do it very
efficiently. In human beings, muscle cells
contract and relax to cause movement, nerve
cells carry messages, blood flows to transport
oxygen, food, hormones and waste material
and so on. In plants, vascular tissues conduct
food and water from one part of the plant to
other parts. So, multi-cellular organisms
show division of labour. Cells specialising in
one function are often grouped together in
the body. This means that a particular
function is carried out by a cluster of cells at
a definite place in the body. This cluster of
cells, called a tissue, is arranged and designed
so as to give the highest possible efficiency of
function. Blood, phloem and muscle are all
examples of tissues.
A group of cells that are similar in
structure and/or work together to achieve a
particular function forms a tissue.
6.1 Are Plants and Animals Made
of Same Types of Tissues?
Let us compare their structure and functions.
Do plants and animals have the same
structure? Do they both perform similar
functions?
There are noticeable differences between
the two. Plants are stationary or fixed – they
don’t move. Most of the tissues they have are
supportive, which provides them with
structural strength. Most of these tissues are
dead, since dead cells can provide mechanical
strength as easily as live ones, and need less
maintenance.
Animals on the other hand move around
in search of food, mates and shelter. They
consume more energy as compared to plants.
Most of the tissues they contain are living.
Another difference between animals and
plants is in the pattern of growth. The growth
in plants is limited to certain regions, while
this is not so in animals. There are some
tissues in plants that divide throughout their
life. These tissues are localised in certain
regions. Based on the dividing capacity of the
tissues, various plant tissues can be classified
as growing or meristematic tissue and
permanent tissue. Cell growth in animals is
more uniform. So, there is no such
demarcation of dividing and non-dividing
regions in animals.
The structural organisation of organs and
organ systems is far more specialised and
localised in complex animals than even in very
complex plants. This fundamental difference
reflects the different modes of life pursued
by these two major groups of organisms,
particularly in their different feeding methods.
Also, they are differently adapted for a
sedentary existence on one hand (plants) and
active locomotion on the other (animals),
contributing to this difference in organ system
design.
It is with reference to these complex
animal and plant bodies that we will now talk
about the concept of tissues in some detail.
6 6
6 6 6
T T T T TISSUES ISSUES ISSUES ISSUES ISSUES
Chapter
uestions
1. What is a tissue?
2. What is the utility of tissues in
multi-cellular organisms?
6.2 Plant Tissues
6.2.1 MERISTEMATIC TISSUE
? From the above observations, answer
the following questions:
1. Which of the two onions has longer
roots? Why?
2. Do the roots continue growing even
after we have removed their tips?
3. Why would the tips stop growing in
jar 2 after we cut them?
The growth of plants occurs only in certain
specific regions. This is because the dividing
tissue, also known as meristematic tissue, is
located only at these points. Depending on
the region where they are present,
meristematic tissues are classified as apical,
lateral and intercalary (Fig. 6.2). New cells
produced by meristem are initially like those
of meristem itself, but as they grow and
mature, their characteristics slowly change
and they become differentiated as
components of other tissues.
Fig. 6.1: Growth of roots in onion bulbs
Activity ______________6.1
? Take two glass jars and fill them with
water.
? Now, take two onion bulbs and place
one on each jar, as shown in
Fig. 6.1.
? Observe the growth of roots in both the
bulbs for a few days.
? Measure the length of roots on day 1,
2 and 3.
? On day 4, cut the root tips of the onion
bulb in jar 2 by about 1 cm. After this,
observe the growth of roots in both the
jars and measure their lengths each
day for five more days and record the
observations in tables, like the table
below:
Length Day 1 Day 2 Day 3 Day 4 Day 5
Jar 1
Jar 2
Q
Apical meristem is present at the growing
tips of stems and roots and increases the
length of the stem and the root. The girth of
the stem or root increases due to lateral
meristem (cambium). Intercalary meristem is
the meristem at the base of the leaves or
internodes (on either side of the node)
on twigs.
Apical meristem
Intercalary meristem
Lateral meristem
Fig. 6.2: Location of meristematic tissue in plant body
Jar 1 Jar 2
TISSUES 69 SCIENCE 70
As the cells of this tissue are very active,
they have dense cytoplasm, thin cellulose
walls and prominent nuclei. They lack
vacuoles. Can we think why they would lack
vacuoles? (You might want to refer to the
functions of vacuoles in the chapter on cells.)
6.2.2 PERMANENT TISSUE
What happens to the cells formed by
meristematic tissue? They take up a specific
role and lose the ability to divide. As a result,
they form a permanent tissue. This process
of taking up a permanent shape, size, and  a
function is called differentiation. Cells of
meristematic tissue differentiate to form
different types of permanent tissue.
? Now, answer the following on the basis
of your observation:
1. Are all cells similar in structure?
2. How many types of cells can
be seen?
3. Can we think of reasons why there
would be so many types of cells?
? We can also try to cut sections of plant
roots. We can even try cutting sections
of root and stem of different plants.
6.2.2 (i) SIMPLE PERMANENT TISSUE
A few layers of cells form the basic packing
tissue. This tissue is parenchyma, a type of
permanent tissue. It consists of relatively
unspecialised cells with thin cell walls. They
are live cells. They are usually loosely packed,
Trichome
Mucilaginous canal
Cuticle
Epidermis
Hypodermis
Cortex
Endodermis
Pericycle
Phloem
Cambium
Metaxylem
Protoxylem
Vascular bundle
Pith
Medullary ray
Xylem
Fig. 6.3: Section of a stem
Activity ______________6.2
? Take a plant stem and  with the help
of your teacher cut into very thin slices
or sections.
? Now, stain the slices with safranin.
Place one neatly cut section on a slide,
and put a drop of glycerine.
? Cover with a cover-slip and observe
under a microscope. Observe the
various types of cells and their
arrangement. Compare it with Fig. 6.3.
so that large spaces between cells
(intercellular  spaces) are found in this tissue
[Fig. 6.4 a(i)]. This tissue provides support to
plants and also stores food. In some
situations, it contains chlorophyll and
performs photosynthesis, and then it is called
chlorenchyma. In aquatic plants, large air
cavities are present in parenchyma to give
buoyancy to the plants to help them float.
Such a parenchyma type is called
aerenchyma. The parenchyma of stems and
roots also stores nutrients and water.
Page 4


From the last chapter, we recall that all living
organisms are made of cells. In unicellular
organisms, a single cell performs all basic
functions. For example, in Amoeba, a single
cell carries out movement, intake of food and
respiratory gases, respiration and excretion.
But in multi-cellular organisms there are
millions of cells. Most of these cells are
specialised to carry out a few functions. Each
specialised function is taken up by a different
group of cells. Since these cells carry out only
a particular function, they do it very
efficiently. In human beings, muscle cells
contract and relax to cause movement, nerve
cells carry messages, blood flows to transport
oxygen, food, hormones and waste material
and so on. In plants, vascular tissues conduct
food and water from one part of the plant to
other parts. So, multi-cellular organisms
show division of labour. Cells specialising in
one function are often grouped together in
the body. This means that a particular
function is carried out by a cluster of cells at
a definite place in the body. This cluster of
cells, called a tissue, is arranged and designed
so as to give the highest possible efficiency of
function. Blood, phloem and muscle are all
examples of tissues.
A group of cells that are similar in
structure and/or work together to achieve a
particular function forms a tissue.
6.1 Are Plants and Animals Made
of Same Types of Tissues?
Let us compare their structure and functions.
Do plants and animals have the same
structure? Do they both perform similar
functions?
There are noticeable differences between
the two. Plants are stationary or fixed – they
don’t move. Most of the tissues they have are
supportive, which provides them with
structural strength. Most of these tissues are
dead, since dead cells can provide mechanical
strength as easily as live ones, and need less
maintenance.
Animals on the other hand move around
in search of food, mates and shelter. They
consume more energy as compared to plants.
Most of the tissues they contain are living.
Another difference between animals and
plants is in the pattern of growth. The growth
in plants is limited to certain regions, while
this is not so in animals. There are some
tissues in plants that divide throughout their
life. These tissues are localised in certain
regions. Based on the dividing capacity of the
tissues, various plant tissues can be classified
as growing or meristematic tissue and
permanent tissue. Cell growth in animals is
more uniform. So, there is no such
demarcation of dividing and non-dividing
regions in animals.
The structural organisation of organs and
organ systems is far more specialised and
localised in complex animals than even in very
complex plants. This fundamental difference
reflects the different modes of life pursued
by these two major groups of organisms,
particularly in their different feeding methods.
Also, they are differently adapted for a
sedentary existence on one hand (plants) and
active locomotion on the other (animals),
contributing to this difference in organ system
design.
It is with reference to these complex
animal and plant bodies that we will now talk
about the concept of tissues in some detail.
6 6
6 6 6
T T T T TISSUES ISSUES ISSUES ISSUES ISSUES
Chapter
uestions
1. What is a tissue?
2. What is the utility of tissues in
multi-cellular organisms?
6.2 Plant Tissues
6.2.1 MERISTEMATIC TISSUE
? From the above observations, answer
the following questions:
1. Which of the two onions has longer
roots? Why?
2. Do the roots continue growing even
after we have removed their tips?
3. Why would the tips stop growing in
jar 2 after we cut them?
The growth of plants occurs only in certain
specific regions. This is because the dividing
tissue, also known as meristematic tissue, is
located only at these points. Depending on
the region where they are present,
meristematic tissues are classified as apical,
lateral and intercalary (Fig. 6.2). New cells
produced by meristem are initially like those
of meristem itself, but as they grow and
mature, their characteristics slowly change
and they become differentiated as
components of other tissues.
Fig. 6.1: Growth of roots in onion bulbs
Activity ______________6.1
? Take two glass jars and fill them with
water.
? Now, take two onion bulbs and place
one on each jar, as shown in
Fig. 6.1.
? Observe the growth of roots in both the
bulbs for a few days.
? Measure the length of roots on day 1,
2 and 3.
? On day 4, cut the root tips of the onion
bulb in jar 2 by about 1 cm. After this,
observe the growth of roots in both the
jars and measure their lengths each
day for five more days and record the
observations in tables, like the table
below:
Length Day 1 Day 2 Day 3 Day 4 Day 5
Jar 1
Jar 2
Q
Apical meristem is present at the growing
tips of stems and roots and increases the
length of the stem and the root. The girth of
the stem or root increases due to lateral
meristem (cambium). Intercalary meristem is
the meristem at the base of the leaves or
internodes (on either side of the node)
on twigs.
Apical meristem
Intercalary meristem
Lateral meristem
Fig. 6.2: Location of meristematic tissue in plant body
Jar 1 Jar 2
TISSUES 69 SCIENCE 70
As the cells of this tissue are very active,
they have dense cytoplasm, thin cellulose
walls and prominent nuclei. They lack
vacuoles. Can we think why they would lack
vacuoles? (You might want to refer to the
functions of vacuoles in the chapter on cells.)
6.2.2 PERMANENT TISSUE
What happens to the cells formed by
meristematic tissue? They take up a specific
role and lose the ability to divide. As a result,
they form a permanent tissue. This process
of taking up a permanent shape, size, and  a
function is called differentiation. Cells of
meristematic tissue differentiate to form
different types of permanent tissue.
? Now, answer the following on the basis
of your observation:
1. Are all cells similar in structure?
2. How many types of cells can
be seen?
3. Can we think of reasons why there
would be so many types of cells?
? We can also try to cut sections of plant
roots. We can even try cutting sections
of root and stem of different plants.
6.2.2 (i) SIMPLE PERMANENT TISSUE
A few layers of cells form the basic packing
tissue. This tissue is parenchyma, a type of
permanent tissue. It consists of relatively
unspecialised cells with thin cell walls. They
are live cells. They are usually loosely packed,
Trichome
Mucilaginous canal
Cuticle
Epidermis
Hypodermis
Cortex
Endodermis
Pericycle
Phloem
Cambium
Metaxylem
Protoxylem
Vascular bundle
Pith
Medullary ray
Xylem
Fig. 6.3: Section of a stem
Activity ______________6.2
? Take a plant stem and  with the help
of your teacher cut into very thin slices
or sections.
? Now, stain the slices with safranin.
Place one neatly cut section on a slide,
and put a drop of glycerine.
? Cover with a cover-slip and observe
under a microscope. Observe the
various types of cells and their
arrangement. Compare it with Fig. 6.3.
so that large spaces between cells
(intercellular  spaces) are found in this tissue
[Fig. 6.4 a(i)]. This tissue provides support to
plants and also stores food. In some
situations, it contains chlorophyll and
performs photosynthesis, and then it is called
chlorenchyma. In aquatic plants, large air
cavities are present in parenchyma to give
buoyancy to the plants to help them float.
Such a parenchyma type is called
aerenchyma. The parenchyma of stems and
roots also stores nutrients and water.
TISSUES 71
Fig. 6.4: Various types of simple tissues: (a) Parenchyma (i) transverse section, (ii) longitudinal section;
(b) Collenchyma (i) transverse section, (ii) longitudinal section; (c) Sclerenchyma (i) transverse section,
(ii) longitudinal section.
b (i)
Wall thickenings
Nucleus
Vacuole
Cell wall
b (ii)
End wall
Primary cell wall
(thickened at corners)
Chloroplast
Nucleus
Vacuole
Cytoplasm
Intercellular space
Cytoplasm
Nucleus
Middle lamella
Chloroplast
Vacuole
Intercellular space
Primary cell wall
a (ii)
a (i)
Intercellular spaces
Narrow lumen
Lignified
thick wall
c (ii)
Simple
pit pair
c (i)
The flexibility in plants is due to another
permanent tissue, collenchyma. It allows
easy bending in various parts of a plant (leaf,
stem) without breaking. It also provides
mechanical support to plants. We can find
this tissue in leaf stalks below the epidermis.
The cells of this tissue are living, elongated
and irregularly thickened at the
corners. There is very little intercellular
space  (Fig. 6.4 b).
Page 5


From the last chapter, we recall that all living
organisms are made of cells. In unicellular
organisms, a single cell performs all basic
functions. For example, in Amoeba, a single
cell carries out movement, intake of food and
respiratory gases, respiration and excretion.
But in multi-cellular organisms there are
millions of cells. Most of these cells are
specialised to carry out a few functions. Each
specialised function is taken up by a different
group of cells. Since these cells carry out only
a particular function, they do it very
efficiently. In human beings, muscle cells
contract and relax to cause movement, nerve
cells carry messages, blood flows to transport
oxygen, food, hormones and waste material
and so on. In plants, vascular tissues conduct
food and water from one part of the plant to
other parts. So, multi-cellular organisms
show division of labour. Cells specialising in
one function are often grouped together in
the body. This means that a particular
function is carried out by a cluster of cells at
a definite place in the body. This cluster of
cells, called a tissue, is arranged and designed
so as to give the highest possible efficiency of
function. Blood, phloem and muscle are all
examples of tissues.
A group of cells that are similar in
structure and/or work together to achieve a
particular function forms a tissue.
6.1 Are Plants and Animals Made
of Same Types of Tissues?
Let us compare their structure and functions.
Do plants and animals have the same
structure? Do they both perform similar
functions?
There are noticeable differences between
the two. Plants are stationary or fixed – they
don’t move. Most of the tissues they have are
supportive, which provides them with
structural strength. Most of these tissues are
dead, since dead cells can provide mechanical
strength as easily as live ones, and need less
maintenance.
Animals on the other hand move around
in search of food, mates and shelter. They
consume more energy as compared to plants.
Most of the tissues they contain are living.
Another difference between animals and
plants is in the pattern of growth. The growth
in plants is limited to certain regions, while
this is not so in animals. There are some
tissues in plants that divide throughout their
life. These tissues are localised in certain
regions. Based on the dividing capacity of the
tissues, various plant tissues can be classified
as growing or meristematic tissue and
permanent tissue. Cell growth in animals is
more uniform. So, there is no such
demarcation of dividing and non-dividing
regions in animals.
The structural organisation of organs and
organ systems is far more specialised and
localised in complex animals than even in very
complex plants. This fundamental difference
reflects the different modes of life pursued
by these two major groups of organisms,
particularly in their different feeding methods.
Also, they are differently adapted for a
sedentary existence on one hand (plants) and
active locomotion on the other (animals),
contributing to this difference in organ system
design.
It is with reference to these complex
animal and plant bodies that we will now talk
about the concept of tissues in some detail.
6 6
6 6 6
T T T T TISSUES ISSUES ISSUES ISSUES ISSUES
Chapter
uestions
1. What is a tissue?
2. What is the utility of tissues in
multi-cellular organisms?
6.2 Plant Tissues
6.2.1 MERISTEMATIC TISSUE
? From the above observations, answer
the following questions:
1. Which of the two onions has longer
roots? Why?
2. Do the roots continue growing even
after we have removed their tips?
3. Why would the tips stop growing in
jar 2 after we cut them?
The growth of plants occurs only in certain
specific regions. This is because the dividing
tissue, also known as meristematic tissue, is
located only at these points. Depending on
the region where they are present,
meristematic tissues are classified as apical,
lateral and intercalary (Fig. 6.2). New cells
produced by meristem are initially like those
of meristem itself, but as they grow and
mature, their characteristics slowly change
and they become differentiated as
components of other tissues.
Fig. 6.1: Growth of roots in onion bulbs
Activity ______________6.1
? Take two glass jars and fill them with
water.
? Now, take two onion bulbs and place
one on each jar, as shown in
Fig. 6.1.
? Observe the growth of roots in both the
bulbs for a few days.
? Measure the length of roots on day 1,
2 and 3.
? On day 4, cut the root tips of the onion
bulb in jar 2 by about 1 cm. After this,
observe the growth of roots in both the
jars and measure their lengths each
day for five more days and record the
observations in tables, like the table
below:
Length Day 1 Day 2 Day 3 Day 4 Day 5
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Q
Apical meristem is present at the growing
tips of stems and roots and increases the
length of the stem and the root. The girth of
the stem or root increases due to lateral
meristem (cambium). Intercalary meristem is
the meristem at the base of the leaves or
internodes (on either side of the node)
on twigs.
Apical meristem
Intercalary meristem
Lateral meristem
Fig. 6.2: Location of meristematic tissue in plant body
Jar 1 Jar 2
TISSUES 69 SCIENCE 70
As the cells of this tissue are very active,
they have dense cytoplasm, thin cellulose
walls and prominent nuclei. They lack
vacuoles. Can we think why they would lack
vacuoles? (You might want to refer to the
functions of vacuoles in the chapter on cells.)
6.2.2 PERMANENT TISSUE
What happens to the cells formed by
meristematic tissue? They take up a specific
role and lose the ability to divide. As a result,
they form a permanent tissue. This process
of taking up a permanent shape, size, and  a
function is called differentiation. Cells of
meristematic tissue differentiate to form
different types of permanent tissue.
? Now, answer the following on the basis
of your observation:
1. Are all cells similar in structure?
2. How many types of cells can
be seen?
3. Can we think of reasons why there
would be so many types of cells?
? We can also try to cut sections of plant
roots. We can even try cutting sections
of root and stem of different plants.
6.2.2 (i) SIMPLE PERMANENT TISSUE
A few layers of cells form the basic packing
tissue. This tissue is parenchyma, a type of
permanent tissue. It consists of relatively
unspecialised cells with thin cell walls. They
are live cells. They are usually loosely packed,
Trichome
Mucilaginous canal
Cuticle
Epidermis
Hypodermis
Cortex
Endodermis
Pericycle
Phloem
Cambium
Metaxylem
Protoxylem
Vascular bundle
Pith
Medullary ray
Xylem
Fig. 6.3: Section of a stem
Activity ______________6.2
? Take a plant stem and  with the help
of your teacher cut into very thin slices
or sections.
? Now, stain the slices with safranin.
Place one neatly cut section on a slide,
and put a drop of glycerine.
? Cover with a cover-slip and observe
under a microscope. Observe the
various types of cells and their
arrangement. Compare it with Fig. 6.3.
so that large spaces between cells
(intercellular  spaces) are found in this tissue
[Fig. 6.4 a(i)]. This tissue provides support to
plants and also stores food. In some
situations, it contains chlorophyll and
performs photosynthesis, and then it is called
chlorenchyma. In aquatic plants, large air
cavities are present in parenchyma to give
buoyancy to the plants to help them float.
Such a parenchyma type is called
aerenchyma. The parenchyma of stems and
roots also stores nutrients and water.
TISSUES 71
Fig. 6.4: Various types of simple tissues: (a) Parenchyma (i) transverse section, (ii) longitudinal section;
(b) Collenchyma (i) transverse section, (ii) longitudinal section; (c) Sclerenchyma (i) transverse section,
(ii) longitudinal section.
b (i)
Wall thickenings
Nucleus
Vacuole
Cell wall
b (ii)
End wall
Primary cell wall
(thickened at corners)
Chloroplast
Nucleus
Vacuole
Cytoplasm
Intercellular space
Cytoplasm
Nucleus
Middle lamella
Chloroplast
Vacuole
Intercellular space
Primary cell wall
a (ii)
a (i)
Intercellular spaces
Narrow lumen
Lignified
thick wall
c (ii)
Simple
pit pair
c (i)
The flexibility in plants is due to another
permanent tissue, collenchyma. It allows
easy bending in various parts of a plant (leaf,
stem) without breaking. It also provides
mechanical support to plants. We can find
this tissue in leaf stalks below the epidermis.
The cells of this tissue are living, elongated
and irregularly thickened at the
corners. There is very little intercellular
space  (Fig. 6.4 b).
SCIENCE 72
Yet another type of permanent tissue is
sclerenchyma. It is the tissue which makes
the plant hard and stiff. We have seen the
husk of a coconut. It is made of
sclerenchymatous tissue. The cells of this
tissue are dead. They are long and narrow as
the walls are thickened due to lignin (a
chemical substance which acts as cement and
hardens them). Often these walls are so thick
that there is no internal space inside the cell
(Fig. 6.4 c). This tissue is present in stems,
around vascular bundles, in the veins of
leaves and in the hard covering of seeds and
nuts. It provides strength to the plant parts.
Activity ______________6.3
? Take a freshly plucked leaf of Rheo.
? Stretch and break it by applying
pressure.
? While breaking it, keep it stretched
gently so that some peel or skin
projects out from the cut.
? Remove this peel and put it in a petri
dish filled with water.
? Add a few drops of safranin.
? Wait for a couple of minutes and then
transfer it onto a slide. Gently place a
cover slip over it.
? Observe under microscope.
epidermis may be thicker since protection
against water loss is critical. The entire
surface of a plant has this outer covering of
epidermis. It protects all the parts of the plant.
Epidermal cells on the aerial parts of the plant
often secrete a waxy, water-resistant layer on
their outer surface. This aids in protection
against loss of water, mechanical injury and
invasion by parasitic fungi. Since it has a
protective role to play, cells of epidermal
tissue form a continuous layer without
intercellular spaces. Most epidermal cells are
relatively flat. Often their outer and side walls
are thicker than the inner wall.
We can observe small pores here and there
in the epidermis of the leaf. These pores are
called stomata (Fig. 6.5). Stomata are
enclosed by two kidney-shaped cells called
guard cells. They are necessary for
exchanging gases with the atmosphere.
Transpiration (loss of water in the form of
water vapour) also takes place through
stomata.
Think about which gas may be required
for photosynthesis.
Find out the role of transpiration in plants.
Epidermal cells of the roots, whose
function is water absorption, commonly bear
long hair-like parts that greatly increase the
total absorptive surface area.
In some plants like desert plants,
epidermis has a thick waxy coating of cutin
(chemical substance with waterproof quality)
on its outer surface. Can we think of a reason
for this?
Is the outer layer of a branch of a tree
different from the outer layer of a young stem?
As plants grow older, the outer protective
tissue undergoes certain changes. A strip of
secondary meristem replaces the epidermis
of the stem. Cells on the outside are cut off
from this layer. This forms the several-layer
thick cork or the bark of the tree. Cells of
cork are dead and compactly arranged
without intercellular spaces (Fig. 6.6). They
also have a chemical called suberin in their
walls that makes them impervious to gases
and water.
Fig. 6.5: Guard cells and epidermal cells: (a)  lateral
view, (b) surface view
(a) (b)
Guard
cell
Stomata
Epidermal
cell
Guard
cells
What you observe is the outermost layer
of cells, called epidermis. The epidermis is
usually made of a single layer of cells. In some
plants living in very dry habitats, the
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