NCERT Textbook - Nutrition in Plants Class 7 Notes | EduRev

General Science(Prelims) by IRS Divey Sethi

Created by: Praveen Kumar

Class 7 : NCERT Textbook - Nutrition in Plants Class 7 Notes | EduRev

 Page 1


Nutrition in Plants Nutrition in Plants Nutrition in Plants Nutrition in Plants Nutrition in Plants
1 1
1 1
1
I
n Class VI you learnt that food is
essential for all living organisms.
You also learnt that carbohydrates,
proteins, fats, vitamins and minerals are
components of food. These components
of food are necessary for our body and
are called nutrients nutrients nutrients nutrients nutrients.
All living organisms require food.
Plants can make their food themselves
but animals including humans cannot.
They get it from plants or animals that
eat plants. Thus, humans and animals
are directly or indirectly dependent on
plants.
1.1 M 1.1 M 1.1 M 1.1 M 1.1 MODE ODE ODE ODE ODE     OF OF OF OF OF     N N N N NUTRITION UTRITION UTRITION UTRITION UTRITION     IN IN IN IN IN     P P P P PLANTS LANTS LANTS LANTS LANTS
Plants are the only organisms that can
prepare food for themselves by using
water, carbon dioxide and minerals. The
raw materials are present in their
surroundings.
The nutrients enable living
organisms to build their bodies, to grow,
to repair damaged parts of their bodies
and provide the energy to carry out life
processes. Nutrition Nutrition Nutrition Nutrition Nutrition is the mode of
taking food by an organism and its
utilisation by the body. The mode of
nutrition in which organisms make food
themselves from simple substances is
called autotrophic autotrophic autotrophic autotrophic autotrophic (auto = self; trophos
= nourishment) nutrition. Therefore,
plants are called autotrophs autotrophs autotrophs autotrophs autotrophs. Animals
and most other organisms take in ready
made food prepared by the plants. They
are called heterotrophs heterotrophs heterotrophs heterotrophs heterotrophs (heteros =
other).
Boojho wants to know
how plants prepare
their own food.
Now we may ask where the food
factories of plants are located: whether
food is made in all parts of a plant or
only in certain parts? How do plants
obtain the raw materials from the
surroundings? How do they transport
them to the food factories of the plants?
1 1 1 1 1.2 .2 .2 .2 .2 P P P P PHOTOSYNTHESIS HOTOSYNTHESIS HOTOSYNTHESIS HOTOSYNTHESIS HOTOSYNTHESIS —  —  —  —  — F F F F FOOD OOD OOD OOD OOD
M M M M MAKING AKING AKING AKING AKING     P P P P PROCESS ROCESS ROCESS ROCESS ROCESS     IN IN IN IN IN     P P P P PLANTS LANTS LANTS LANTS LANTS
Leaves are the food factories of plants.
The synthesis of food in plants occurs
in leaves. Therefore, all the raw
materials must reach there. Water and
minerals present in the soil are absorbed
by the roots and transported to the
Paheli wants to know why
our body cannot make food
from carbon dioxide, water
and minerals like plants do.
Page 2


Nutrition in Plants Nutrition in Plants Nutrition in Plants Nutrition in Plants Nutrition in Plants
1 1
1 1
1
I
n Class VI you learnt that food is
essential for all living organisms.
You also learnt that carbohydrates,
proteins, fats, vitamins and minerals are
components of food. These components
of food are necessary for our body and
are called nutrients nutrients nutrients nutrients nutrients.
All living organisms require food.
Plants can make their food themselves
but animals including humans cannot.
They get it from plants or animals that
eat plants. Thus, humans and animals
are directly or indirectly dependent on
plants.
1.1 M 1.1 M 1.1 M 1.1 M 1.1 MODE ODE ODE ODE ODE     OF OF OF OF OF     N N N N NUTRITION UTRITION UTRITION UTRITION UTRITION     IN IN IN IN IN     P P P P PLANTS LANTS LANTS LANTS LANTS
Plants are the only organisms that can
prepare food for themselves by using
water, carbon dioxide and minerals. The
raw materials are present in their
surroundings.
The nutrients enable living
organisms to build their bodies, to grow,
to repair damaged parts of their bodies
and provide the energy to carry out life
processes. Nutrition Nutrition Nutrition Nutrition Nutrition is the mode of
taking food by an organism and its
utilisation by the body. The mode of
nutrition in which organisms make food
themselves from simple substances is
called autotrophic autotrophic autotrophic autotrophic autotrophic (auto = self; trophos
= nourishment) nutrition. Therefore,
plants are called autotrophs autotrophs autotrophs autotrophs autotrophs. Animals
and most other organisms take in ready
made food prepared by the plants. They
are called heterotrophs heterotrophs heterotrophs heterotrophs heterotrophs (heteros =
other).
Boojho wants to know
how plants prepare
their own food.
Now we may ask where the food
factories of plants are located: whether
food is made in all parts of a plant or
only in certain parts? How do plants
obtain the raw materials from the
surroundings? How do they transport
them to the food factories of the plants?
1 1 1 1 1.2 .2 .2 .2 .2 P P P P PHOTOSYNTHESIS HOTOSYNTHESIS HOTOSYNTHESIS HOTOSYNTHESIS HOTOSYNTHESIS —  —  —  —  — F F F F FOOD OOD OOD OOD OOD
M M M M MAKING AKING AKING AKING AKING     P P P P PROCESS ROCESS ROCESS ROCESS ROCESS     IN IN IN IN IN     P P P P PLANTS LANTS LANTS LANTS LANTS
Leaves are the food factories of plants.
The synthesis of food in plants occurs
in leaves. Therefore, all the raw
materials must reach there. Water and
minerals present in the soil are absorbed
by the roots and transported to the
Paheli wants to know why
our body cannot make food
from carbon dioxide, water
and minerals like plants do.
S S S S SCIENCE CIENCE CIENCE CIENCE CIENCE 2 2 2 2 2
Paheli wants to know what is so
special about the leaves that they
can synthesise food but  other
parts of the plant cannot.
Boojho wants to know how water
and minerals absorbed by roots
reach the leaves.
Cells Cells Cells Cells Cells
leaves. Carbon dioxide from air is taken
in through the tiny pores present on the
surface of the leaves. These pores are
surrounded by ‘guard cells’. Such pores
are called stomata stomata stomata stomata stomata [Fig. 1.2 (c)].
Water and minerals are transported
to the leaves by the vessels which run
like pipes throughout the root, the stem,
the branches and the leaves. They form
a continuous path or passage for the
nutrients to reach the leaf. You will learn
about transport of materials in plants
in Chapter 11.
The leaves have a green pigment green pigment green pigment green pigment green pigment
called chlorophyll chlorophyll chlorophyll chlorophyll chlorophyll. It helps leaves to
capture the energy of the sunlight. This
energy is used to synthesise (prepare)
food from carbon dioxide and water.
Since the synthesis of food occurs in the
presence of sunlight, it is called
photosynthesis photosynthesis photosynthesis photosynthesis photosynthesis (Photo: light; synthesis :
to combine). So we find that chlorophyll,
sunlight, carbon dioxide and water are
necessary to carry out the process of
photosynthesis. It is a unique process
on the earth. The solar energy is
captured by the leaves and stored in the
plant in the form of food. Thus, sun is Thus, sun is Thus, sun is Thus, sun is Thus, sun is
the ultimate source of energy for all the ultimate source of energy for all the ultimate source of energy for all the ultimate source of energy for all the ultimate source of energy for all
living organisms living organisms living organisms living organisms living organisms.
Can you imagine the earth in the
absence of photosynthesis!
In the absence of photosynthesis
there would not be any plants. The
survival of almost all living organisms
directly or indirectly depends upon the
food made by the plants. Besides,
oxygen which is essential for the survival
You have seen that buildings are made of bricks.
Similarly, the bodies of living organisms are
made of tiny units called cells cells cells cells cells. Cells can be seen
only under the microscope. Some organisms
are made of only one cell. The cell is enclosed by
a thin outer boundary, called the cell membrane cell membrane cell membrane cell membrane cell membrane.
Most cells have a distinct, centrally located
spherical structure called the nucleus nucleus nucleus nucleus nucleus (Fig. 1.1).
The nucleus is surrounded by a jelly-like
substance called cytoplasm cytoplasm cytoplasm cytoplasm cytoplasm.
Cell membrane
Cytoplasm
Nucleus
Fig. 1.1 Fig. 1.1 Fig. 1.1 Fig. 1.1 Fig. 1.1 Cell
Page 3


Nutrition in Plants Nutrition in Plants Nutrition in Plants Nutrition in Plants Nutrition in Plants
1 1
1 1
1
I
n Class VI you learnt that food is
essential for all living organisms.
You also learnt that carbohydrates,
proteins, fats, vitamins and minerals are
components of food. These components
of food are necessary for our body and
are called nutrients nutrients nutrients nutrients nutrients.
All living organisms require food.
Plants can make their food themselves
but animals including humans cannot.
They get it from plants or animals that
eat plants. Thus, humans and animals
are directly or indirectly dependent on
plants.
1.1 M 1.1 M 1.1 M 1.1 M 1.1 MODE ODE ODE ODE ODE     OF OF OF OF OF     N N N N NUTRITION UTRITION UTRITION UTRITION UTRITION     IN IN IN IN IN     P P P P PLANTS LANTS LANTS LANTS LANTS
Plants are the only organisms that can
prepare food for themselves by using
water, carbon dioxide and minerals. The
raw materials are present in their
surroundings.
The nutrients enable living
organisms to build their bodies, to grow,
to repair damaged parts of their bodies
and provide the energy to carry out life
processes. Nutrition Nutrition Nutrition Nutrition Nutrition is the mode of
taking food by an organism and its
utilisation by the body. The mode of
nutrition in which organisms make food
themselves from simple substances is
called autotrophic autotrophic autotrophic autotrophic autotrophic (auto = self; trophos
= nourishment) nutrition. Therefore,
plants are called autotrophs autotrophs autotrophs autotrophs autotrophs. Animals
and most other organisms take in ready
made food prepared by the plants. They
are called heterotrophs heterotrophs heterotrophs heterotrophs heterotrophs (heteros =
other).
Boojho wants to know
how plants prepare
their own food.
Now we may ask where the food
factories of plants are located: whether
food is made in all parts of a plant or
only in certain parts? How do plants
obtain the raw materials from the
surroundings? How do they transport
them to the food factories of the plants?
1 1 1 1 1.2 .2 .2 .2 .2 P P P P PHOTOSYNTHESIS HOTOSYNTHESIS HOTOSYNTHESIS HOTOSYNTHESIS HOTOSYNTHESIS —  —  —  —  — F F F F FOOD OOD OOD OOD OOD
M M M M MAKING AKING AKING AKING AKING     P P P P PROCESS ROCESS ROCESS ROCESS ROCESS     IN IN IN IN IN     P P P P PLANTS LANTS LANTS LANTS LANTS
Leaves are the food factories of plants.
The synthesis of food in plants occurs
in leaves. Therefore, all the raw
materials must reach there. Water and
minerals present in the soil are absorbed
by the roots and transported to the
Paheli wants to know why
our body cannot make food
from carbon dioxide, water
and minerals like plants do.
S S S S SCIENCE CIENCE CIENCE CIENCE CIENCE 2 2 2 2 2
Paheli wants to know what is so
special about the leaves that they
can synthesise food but  other
parts of the plant cannot.
Boojho wants to know how water
and minerals absorbed by roots
reach the leaves.
Cells Cells Cells Cells Cells
leaves. Carbon dioxide from air is taken
in through the tiny pores present on the
surface of the leaves. These pores are
surrounded by ‘guard cells’. Such pores
are called stomata stomata stomata stomata stomata [Fig. 1.2 (c)].
Water and minerals are transported
to the leaves by the vessels which run
like pipes throughout the root, the stem,
the branches and the leaves. They form
a continuous path or passage for the
nutrients to reach the leaf. You will learn
about transport of materials in plants
in Chapter 11.
The leaves have a green pigment green pigment green pigment green pigment green pigment
called chlorophyll chlorophyll chlorophyll chlorophyll chlorophyll. It helps leaves to
capture the energy of the sunlight. This
energy is used to synthesise (prepare)
food from carbon dioxide and water.
Since the synthesis of food occurs in the
presence of sunlight, it is called
photosynthesis photosynthesis photosynthesis photosynthesis photosynthesis (Photo: light; synthesis :
to combine). So we find that chlorophyll,
sunlight, carbon dioxide and water are
necessary to carry out the process of
photosynthesis. It is a unique process
on the earth. The solar energy is
captured by the leaves and stored in the
plant in the form of food. Thus, sun is Thus, sun is Thus, sun is Thus, sun is Thus, sun is
the ultimate source of energy for all the ultimate source of energy for all the ultimate source of energy for all the ultimate source of energy for all the ultimate source of energy for all
living organisms living organisms living organisms living organisms living organisms.
Can you imagine the earth in the
absence of photosynthesis!
In the absence of photosynthesis
there would not be any plants. The
survival of almost all living organisms
directly or indirectly depends upon the
food made by the plants. Besides,
oxygen which is essential for the survival
You have seen that buildings are made of bricks.
Similarly, the bodies of living organisms are
made of tiny units called cells cells cells cells cells. Cells can be seen
only under the microscope. Some organisms
are made of only one cell. The cell is enclosed by
a thin outer boundary, called the cell membrane cell membrane cell membrane cell membrane cell membrane.
Most cells have a distinct, centrally located
spherical structure called the nucleus nucleus nucleus nucleus nucleus (Fig. 1.1).
The nucleus is surrounded by a jelly-like
substance called cytoplasm cytoplasm cytoplasm cytoplasm cytoplasm.
Cell membrane
Cytoplasm
Nucleus
Fig. 1.1 Fig. 1.1 Fig. 1.1 Fig. 1.1 Fig. 1.1 Cell
N N N N NUTRITION UTRITION UTRITION UTRITION UTRITION     IN IN IN IN IN P P P P PLANTS LANTS LANTS LANTS LANTS 3 3 3 3 3
Besides leaves, photosynthesis also takes place in other green parts of the
plant — in green stems and green branches. The desert plants have scale- or
spine-like leaves to reduce loss of water by transpiration. These plants have
green stems which carry out photosynthesis.
of all living organisms is produced
during photosynthesis. In the absence
of photosynthesis, life would be
impossible on the earth.
During photosynthesis, chlorophyll
containing cells of leaves (Fig. 1.2), in
the presence of sunlight, use carbon
dioxide and water to synthesise
carbohydrates (Fig. 1.3). The process
can be represented as an equation:
During the process oxygen is
released. The carbohydrates ultimately
get converted into starch. The presence
of starch in leaves indicates the
occurrence of photosynthesis. The
starch is also a carbohydrate.
Fig. 1.2 Fig. 1.2 Fig. 1.2 Fig. 1.2 Fig. 1.2
(a) Leaf
Fig. 1.3 Fig. 1.3 Fig. 1.3 Fig. 1.3 Fig. 1.3  Schematic diagram showing
photosynthesis
Light energy
Carbon
dioxide
Oxygen
Chlorophyll
in leaf
Water and
minerals
        
 
sunlight
chlorophyll
Carbon dioxide water 
Carbohydrate oxygen
Boojho has observed some
plants with deep red, violet or
brown leaves. He wants to
know whether these leaves
also carry out photosynthesis.
Guard cells
(c) Stomata
Stomatal opening
Chlorophyll
(b) A section through a leaf
Stoma Guard cell
Activity 1.1 Activity 1.1 Activity 1.1 Activity 1.1 Activity 1.1
Take two potted plants of the same kind.
Keep one in the dark (or in a black box)
for 72 hours and the other in the
Page 4


Nutrition in Plants Nutrition in Plants Nutrition in Plants Nutrition in Plants Nutrition in Plants
1 1
1 1
1
I
n Class VI you learnt that food is
essential for all living organisms.
You also learnt that carbohydrates,
proteins, fats, vitamins and minerals are
components of food. These components
of food are necessary for our body and
are called nutrients nutrients nutrients nutrients nutrients.
All living organisms require food.
Plants can make their food themselves
but animals including humans cannot.
They get it from plants or animals that
eat plants. Thus, humans and animals
are directly or indirectly dependent on
plants.
1.1 M 1.1 M 1.1 M 1.1 M 1.1 MODE ODE ODE ODE ODE     OF OF OF OF OF     N N N N NUTRITION UTRITION UTRITION UTRITION UTRITION     IN IN IN IN IN     P P P P PLANTS LANTS LANTS LANTS LANTS
Plants are the only organisms that can
prepare food for themselves by using
water, carbon dioxide and minerals. The
raw materials are present in their
surroundings.
The nutrients enable living
organisms to build their bodies, to grow,
to repair damaged parts of their bodies
and provide the energy to carry out life
processes. Nutrition Nutrition Nutrition Nutrition Nutrition is the mode of
taking food by an organism and its
utilisation by the body. The mode of
nutrition in which organisms make food
themselves from simple substances is
called autotrophic autotrophic autotrophic autotrophic autotrophic (auto = self; trophos
= nourishment) nutrition. Therefore,
plants are called autotrophs autotrophs autotrophs autotrophs autotrophs. Animals
and most other organisms take in ready
made food prepared by the plants. They
are called heterotrophs heterotrophs heterotrophs heterotrophs heterotrophs (heteros =
other).
Boojho wants to know
how plants prepare
their own food.
Now we may ask where the food
factories of plants are located: whether
food is made in all parts of a plant or
only in certain parts? How do plants
obtain the raw materials from the
surroundings? How do they transport
them to the food factories of the plants?
1 1 1 1 1.2 .2 .2 .2 .2 P P P P PHOTOSYNTHESIS HOTOSYNTHESIS HOTOSYNTHESIS HOTOSYNTHESIS HOTOSYNTHESIS —  —  —  —  — F F F F FOOD OOD OOD OOD OOD
M M M M MAKING AKING AKING AKING AKING     P P P P PROCESS ROCESS ROCESS ROCESS ROCESS     IN IN IN IN IN     P P P P PLANTS LANTS LANTS LANTS LANTS
Leaves are the food factories of plants.
The synthesis of food in plants occurs
in leaves. Therefore, all the raw
materials must reach there. Water and
minerals present in the soil are absorbed
by the roots and transported to the
Paheli wants to know why
our body cannot make food
from carbon dioxide, water
and minerals like plants do.
S S S S SCIENCE CIENCE CIENCE CIENCE CIENCE 2 2 2 2 2
Paheli wants to know what is so
special about the leaves that they
can synthesise food but  other
parts of the plant cannot.
Boojho wants to know how water
and minerals absorbed by roots
reach the leaves.
Cells Cells Cells Cells Cells
leaves. Carbon dioxide from air is taken
in through the tiny pores present on the
surface of the leaves. These pores are
surrounded by ‘guard cells’. Such pores
are called stomata stomata stomata stomata stomata [Fig. 1.2 (c)].
Water and minerals are transported
to the leaves by the vessels which run
like pipes throughout the root, the stem,
the branches and the leaves. They form
a continuous path or passage for the
nutrients to reach the leaf. You will learn
about transport of materials in plants
in Chapter 11.
The leaves have a green pigment green pigment green pigment green pigment green pigment
called chlorophyll chlorophyll chlorophyll chlorophyll chlorophyll. It helps leaves to
capture the energy of the sunlight. This
energy is used to synthesise (prepare)
food from carbon dioxide and water.
Since the synthesis of food occurs in the
presence of sunlight, it is called
photosynthesis photosynthesis photosynthesis photosynthesis photosynthesis (Photo: light; synthesis :
to combine). So we find that chlorophyll,
sunlight, carbon dioxide and water are
necessary to carry out the process of
photosynthesis. It is a unique process
on the earth. The solar energy is
captured by the leaves and stored in the
plant in the form of food. Thus, sun is Thus, sun is Thus, sun is Thus, sun is Thus, sun is
the ultimate source of energy for all the ultimate source of energy for all the ultimate source of energy for all the ultimate source of energy for all the ultimate source of energy for all
living organisms living organisms living organisms living organisms living organisms.
Can you imagine the earth in the
absence of photosynthesis!
In the absence of photosynthesis
there would not be any plants. The
survival of almost all living organisms
directly or indirectly depends upon the
food made by the plants. Besides,
oxygen which is essential for the survival
You have seen that buildings are made of bricks.
Similarly, the bodies of living organisms are
made of tiny units called cells cells cells cells cells. Cells can be seen
only under the microscope. Some organisms
are made of only one cell. The cell is enclosed by
a thin outer boundary, called the cell membrane cell membrane cell membrane cell membrane cell membrane.
Most cells have a distinct, centrally located
spherical structure called the nucleus nucleus nucleus nucleus nucleus (Fig. 1.1).
The nucleus is surrounded by a jelly-like
substance called cytoplasm cytoplasm cytoplasm cytoplasm cytoplasm.
Cell membrane
Cytoplasm
Nucleus
Fig. 1.1 Fig. 1.1 Fig. 1.1 Fig. 1.1 Fig. 1.1 Cell
N N N N NUTRITION UTRITION UTRITION UTRITION UTRITION     IN IN IN IN IN P P P P PLANTS LANTS LANTS LANTS LANTS 3 3 3 3 3
Besides leaves, photosynthesis also takes place in other green parts of the
plant — in green stems and green branches. The desert plants have scale- or
spine-like leaves to reduce loss of water by transpiration. These plants have
green stems which carry out photosynthesis.
of all living organisms is produced
during photosynthesis. In the absence
of photosynthesis, life would be
impossible on the earth.
During photosynthesis, chlorophyll
containing cells of leaves (Fig. 1.2), in
the presence of sunlight, use carbon
dioxide and water to synthesise
carbohydrates (Fig. 1.3). The process
can be represented as an equation:
During the process oxygen is
released. The carbohydrates ultimately
get converted into starch. The presence
of starch in leaves indicates the
occurrence of photosynthesis. The
starch is also a carbohydrate.
Fig. 1.2 Fig. 1.2 Fig. 1.2 Fig. 1.2 Fig. 1.2
(a) Leaf
Fig. 1.3 Fig. 1.3 Fig. 1.3 Fig. 1.3 Fig. 1.3  Schematic diagram showing
photosynthesis
Light energy
Carbon
dioxide
Oxygen
Chlorophyll
in leaf
Water and
minerals
        
 
sunlight
chlorophyll
Carbon dioxide water 
Carbohydrate oxygen
Boojho has observed some
plants with deep red, violet or
brown leaves. He wants to
know whether these leaves
also carry out photosynthesis.
Guard cells
(c) Stomata
Stomatal opening
Chlorophyll
(b) A section through a leaf
Stoma Guard cell
Activity 1.1 Activity 1.1 Activity 1.1 Activity 1.1 Activity 1.1
Take two potted plants of the same kind.
Keep one in the dark (or in a black box)
for 72 hours and the other in the
S S S S SCIENCE CIENCE CIENCE CIENCE CIENCE 4 4 4 4 4
Fig. 1.4  Fig. 1.4  Fig. 1.4  Fig. 1.4  Fig. 1.4  Leaves of various colours
process of photosynthesis. The
carbohydrates are made of carbon,
hydrogen and oxygen. These are used
to synthesise other components of food.
But proteins are nitrogenous substances
which contain nitrogen. From where do
the plants obtain nitrogen?
Recall that nitrogen is present in
abundance in gaseous form in the air.
However, plants cannot absorb nitrogen
in this form. Soil has certain bacteria
that convert gaseous nitrogen into a
usable form and release it into the soil.
These soluble forms are absorbed by the
plants along with water. Also, you might
have seen farmers adding fertilisers rich
in nitrogen to the soil. In this way the
plants fulfil their requirements of
nitrogen along with the other
constituents. Plants can then
synthesise components of food other
than carbohydrates such as proteins
and fats.
1.3 O 1.3 O 1.3 O 1.3 O 1.3 OTHER THER THER THER THER M M M M MODES ODES ODES ODES ODES     OF OF OF OF OF N N N N NUTRITION UTRITION UTRITION UTRITION UTRITION     IN IN IN IN IN
P P P P PLANTS LANTS LANTS LANTS LANTS
There are some plants which do not have
chlorophyll. They cannot synthesise
their food. How do they survive and from
where do they derive nutrition? Like
humans and animals such plants
depend on the food produced by other
plants. They use the heterotrophic heterotrophic heterotrophic heterotrophic heterotrophic
mode mode mode mode mode of nutrition. Look at Fig. 1.5. Do
you see yellow tubular structures
twining around the stem and branches
of a tree? This is a plant called Cuscuta
(Amarbel). It does not have chlorophyll.
It takes readymade food from the plant
You often see slimy, green patches
in ponds or in other stagnant water
bodies. These are generally formed by
the growth of organisms called algae algae algae algae algae.
Can you guess why algae are green in
colour? They contain chlorophyll which
gives them the green colour. Algae can
also prepare their own food by
photosynthesis.
Synthesis of plant food other Synthesis of plant food other Synthesis of plant food other Synthesis of plant food other Synthesis of plant food other
than carbohydrates than carbohydrates than carbohydrates than carbohydrates than carbohydrates
You have just learnt that plants
synthesise carbohydrates through the
sunlight. Perform iodine test with the
leaves of both the plants as you did in
Class VI. Record your results. Now leave
the pot which was earlier kept in the
dark, in the sunlight for 3 – 4 days and
perform the iodine test again on its
leaves. Record your observations in your
notebook.
The leaves other than green also have
chlorophyll. The large amount of red,
brown and other pigments mask the
green colour (Fig. 1.4). Photosynthesis
takes place in these leaves also.
Page 5


Nutrition in Plants Nutrition in Plants Nutrition in Plants Nutrition in Plants Nutrition in Plants
1 1
1 1
1
I
n Class VI you learnt that food is
essential for all living organisms.
You also learnt that carbohydrates,
proteins, fats, vitamins and minerals are
components of food. These components
of food are necessary for our body and
are called nutrients nutrients nutrients nutrients nutrients.
All living organisms require food.
Plants can make their food themselves
but animals including humans cannot.
They get it from plants or animals that
eat plants. Thus, humans and animals
are directly or indirectly dependent on
plants.
1.1 M 1.1 M 1.1 M 1.1 M 1.1 MODE ODE ODE ODE ODE     OF OF OF OF OF     N N N N NUTRITION UTRITION UTRITION UTRITION UTRITION     IN IN IN IN IN     P P P P PLANTS LANTS LANTS LANTS LANTS
Plants are the only organisms that can
prepare food for themselves by using
water, carbon dioxide and minerals. The
raw materials are present in their
surroundings.
The nutrients enable living
organisms to build their bodies, to grow,
to repair damaged parts of their bodies
and provide the energy to carry out life
processes. Nutrition Nutrition Nutrition Nutrition Nutrition is the mode of
taking food by an organism and its
utilisation by the body. The mode of
nutrition in which organisms make food
themselves from simple substances is
called autotrophic autotrophic autotrophic autotrophic autotrophic (auto = self; trophos
= nourishment) nutrition. Therefore,
plants are called autotrophs autotrophs autotrophs autotrophs autotrophs. Animals
and most other organisms take in ready
made food prepared by the plants. They
are called heterotrophs heterotrophs heterotrophs heterotrophs heterotrophs (heteros =
other).
Boojho wants to know
how plants prepare
their own food.
Now we may ask where the food
factories of plants are located: whether
food is made in all parts of a plant or
only in certain parts? How do plants
obtain the raw materials from the
surroundings? How do they transport
them to the food factories of the plants?
1 1 1 1 1.2 .2 .2 .2 .2 P P P P PHOTOSYNTHESIS HOTOSYNTHESIS HOTOSYNTHESIS HOTOSYNTHESIS HOTOSYNTHESIS —  —  —  —  — F F F F FOOD OOD OOD OOD OOD
M M M M MAKING AKING AKING AKING AKING     P P P P PROCESS ROCESS ROCESS ROCESS ROCESS     IN IN IN IN IN     P P P P PLANTS LANTS LANTS LANTS LANTS
Leaves are the food factories of plants.
The synthesis of food in plants occurs
in leaves. Therefore, all the raw
materials must reach there. Water and
minerals present in the soil are absorbed
by the roots and transported to the
Paheli wants to know why
our body cannot make food
from carbon dioxide, water
and minerals like plants do.
S S S S SCIENCE CIENCE CIENCE CIENCE CIENCE 2 2 2 2 2
Paheli wants to know what is so
special about the leaves that they
can synthesise food but  other
parts of the plant cannot.
Boojho wants to know how water
and minerals absorbed by roots
reach the leaves.
Cells Cells Cells Cells Cells
leaves. Carbon dioxide from air is taken
in through the tiny pores present on the
surface of the leaves. These pores are
surrounded by ‘guard cells’. Such pores
are called stomata stomata stomata stomata stomata [Fig. 1.2 (c)].
Water and minerals are transported
to the leaves by the vessels which run
like pipes throughout the root, the stem,
the branches and the leaves. They form
a continuous path or passage for the
nutrients to reach the leaf. You will learn
about transport of materials in plants
in Chapter 11.
The leaves have a green pigment green pigment green pigment green pigment green pigment
called chlorophyll chlorophyll chlorophyll chlorophyll chlorophyll. It helps leaves to
capture the energy of the sunlight. This
energy is used to synthesise (prepare)
food from carbon dioxide and water.
Since the synthesis of food occurs in the
presence of sunlight, it is called
photosynthesis photosynthesis photosynthesis photosynthesis photosynthesis (Photo: light; synthesis :
to combine). So we find that chlorophyll,
sunlight, carbon dioxide and water are
necessary to carry out the process of
photosynthesis. It is a unique process
on the earth. The solar energy is
captured by the leaves and stored in the
plant in the form of food. Thus, sun is Thus, sun is Thus, sun is Thus, sun is Thus, sun is
the ultimate source of energy for all the ultimate source of energy for all the ultimate source of energy for all the ultimate source of energy for all the ultimate source of energy for all
living organisms living organisms living organisms living organisms living organisms.
Can you imagine the earth in the
absence of photosynthesis!
In the absence of photosynthesis
there would not be any plants. The
survival of almost all living organisms
directly or indirectly depends upon the
food made by the plants. Besides,
oxygen which is essential for the survival
You have seen that buildings are made of bricks.
Similarly, the bodies of living organisms are
made of tiny units called cells cells cells cells cells. Cells can be seen
only under the microscope. Some organisms
are made of only one cell. The cell is enclosed by
a thin outer boundary, called the cell membrane cell membrane cell membrane cell membrane cell membrane.
Most cells have a distinct, centrally located
spherical structure called the nucleus nucleus nucleus nucleus nucleus (Fig. 1.1).
The nucleus is surrounded by a jelly-like
substance called cytoplasm cytoplasm cytoplasm cytoplasm cytoplasm.
Cell membrane
Cytoplasm
Nucleus
Fig. 1.1 Fig. 1.1 Fig. 1.1 Fig. 1.1 Fig. 1.1 Cell
N N N N NUTRITION UTRITION UTRITION UTRITION UTRITION     IN IN IN IN IN P P P P PLANTS LANTS LANTS LANTS LANTS 3 3 3 3 3
Besides leaves, photosynthesis also takes place in other green parts of the
plant — in green stems and green branches. The desert plants have scale- or
spine-like leaves to reduce loss of water by transpiration. These plants have
green stems which carry out photosynthesis.
of all living organisms is produced
during photosynthesis. In the absence
of photosynthesis, life would be
impossible on the earth.
During photosynthesis, chlorophyll
containing cells of leaves (Fig. 1.2), in
the presence of sunlight, use carbon
dioxide and water to synthesise
carbohydrates (Fig. 1.3). The process
can be represented as an equation:
During the process oxygen is
released. The carbohydrates ultimately
get converted into starch. The presence
of starch in leaves indicates the
occurrence of photosynthesis. The
starch is also a carbohydrate.
Fig. 1.2 Fig. 1.2 Fig. 1.2 Fig. 1.2 Fig. 1.2
(a) Leaf
Fig. 1.3 Fig. 1.3 Fig. 1.3 Fig. 1.3 Fig. 1.3  Schematic diagram showing
photosynthesis
Light energy
Carbon
dioxide
Oxygen
Chlorophyll
in leaf
Water and
minerals
        
 
sunlight
chlorophyll
Carbon dioxide water 
Carbohydrate oxygen
Boojho has observed some
plants with deep red, violet or
brown leaves. He wants to
know whether these leaves
also carry out photosynthesis.
Guard cells
(c) Stomata
Stomatal opening
Chlorophyll
(b) A section through a leaf
Stoma Guard cell
Activity 1.1 Activity 1.1 Activity 1.1 Activity 1.1 Activity 1.1
Take two potted plants of the same kind.
Keep one in the dark (or in a black box)
for 72 hours and the other in the
S S S S SCIENCE CIENCE CIENCE CIENCE CIENCE 4 4 4 4 4
Fig. 1.4  Fig. 1.4  Fig. 1.4  Fig. 1.4  Fig. 1.4  Leaves of various colours
process of photosynthesis. The
carbohydrates are made of carbon,
hydrogen and oxygen. These are used
to synthesise other components of food.
But proteins are nitrogenous substances
which contain nitrogen. From where do
the plants obtain nitrogen?
Recall that nitrogen is present in
abundance in gaseous form in the air.
However, plants cannot absorb nitrogen
in this form. Soil has certain bacteria
that convert gaseous nitrogen into a
usable form and release it into the soil.
These soluble forms are absorbed by the
plants along with water. Also, you might
have seen farmers adding fertilisers rich
in nitrogen to the soil. In this way the
plants fulfil their requirements of
nitrogen along with the other
constituents. Plants can then
synthesise components of food other
than carbohydrates such as proteins
and fats.
1.3 O 1.3 O 1.3 O 1.3 O 1.3 OTHER THER THER THER THER M M M M MODES ODES ODES ODES ODES     OF OF OF OF OF N N N N NUTRITION UTRITION UTRITION UTRITION UTRITION     IN IN IN IN IN
P P P P PLANTS LANTS LANTS LANTS LANTS
There are some plants which do not have
chlorophyll. They cannot synthesise
their food. How do they survive and from
where do they derive nutrition? Like
humans and animals such plants
depend on the food produced by other
plants. They use the heterotrophic heterotrophic heterotrophic heterotrophic heterotrophic
mode mode mode mode mode of nutrition. Look at Fig. 1.5. Do
you see yellow tubular structures
twining around the stem and branches
of a tree? This is a plant called Cuscuta
(Amarbel). It does not have chlorophyll.
It takes readymade food from the plant
You often see slimy, green patches
in ponds or in other stagnant water
bodies. These are generally formed by
the growth of organisms called algae algae algae algae algae.
Can you guess why algae are green in
colour? They contain chlorophyll which
gives them the green colour. Algae can
also prepare their own food by
photosynthesis.
Synthesis of plant food other Synthesis of plant food other Synthesis of plant food other Synthesis of plant food other Synthesis of plant food other
than carbohydrates than carbohydrates than carbohydrates than carbohydrates than carbohydrates
You have just learnt that plants
synthesise carbohydrates through the
sunlight. Perform iodine test with the
leaves of both the plants as you did in
Class VI. Record your results. Now leave
the pot which was earlier kept in the
dark, in the sunlight for 3 – 4 days and
perform the iodine test again on its
leaves. Record your observations in your
notebook.
The leaves other than green also have
chlorophyll. The large amount of red,
brown and other pigments mask the
green colour (Fig. 1.4). Photosynthesis
takes place in these leaves also.
N N N N NUTRITION UTRITION UTRITION UTRITION UTRITION     IN IN IN IN IN P P P P PLANTS LANTS LANTS LANTS LANTS 5 5 5 5 5
on which it is climbing. The plant on
which it climbs is called a host host host host host. Since it
deprives the host of valuable nutrients,
it is called a parasite parasite parasite parasite parasite. Are we and the
other animals also parasites for the
plants? You should think about it and
discuss with your teacher.
structure is the modified part of the leaf.
The apex of the leaf forms a lid which
can open and close the mouth of the
pitcher. Inside the pitcher there are hair
which are directed downwards. When
an insect lands in the pitcher, the lid
closes and the trapped insect gets
entangled into the hair. The insect is
digested by the digestive juices secreted
in the pitcher. Such insect-eating plants
are called insectivorous insectivorous insectivorous insectivorous insectivorous plants plants plants plants plants.
Is it possible that such plants do not
get all the required nutrients from the
soil in which they grow?
Fig. 1.5 Fig. 1.5 Fig. 1.5 Fig. 1.5 Fig. 1.5  Cuscuta (Amarbel) on host plant
Paheli wants to know whether
mosquitoes, bed bugs, lice and
leeches that suck our blood are
also parasites.
Fig. 1.6 Fig. 1.6 Fig. 1.6 Fig. 1.6 Fig. 1.6  Pitcher plant showing lid and pitcher
Leaf modified
into pitcher
Lid
Boojho is confused. If the
pitcher plant is green and
carries out photosynthesis, then
why does it feed on insects?
Have you seen or heard of plants that
can eat animals? There are a few plants
which can trap insects and digest them.
Is it not amazing? Such plants may be
green or of some other colour. Look at
the plant in Fig. 1.6. The pitcher-like
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