Nutrition in Plants
Food is the most important and basic thing for life. Carbohydrates, proteins,
fats, vitamins and minerals are the components of food. These components are
necessary for all living beings. All plants and animals require food for their
growth and getting energy. The process of utilization of food by an animal to
obtain energy for growth and development is known as nutrition. Plants make
their food themselves but animals cannot. Hence, animals depend directly or
indirectly on the plant.
1. What are the components of food?
Answer – Carbohydrates, proteins, fats, vitamins and minerals are the components
2. What is nutrition?
Answer – The process of utilization of food by a living organism to obtain
energy is called nutrition.
3. Why is need of nutrition?
Answer – Animals do not make their food themselves which plants do. Animals eat
plants or plant eating animals. Hence, animals are directly or indirectly depend
Mode of nutrition in plant
Autotrophic Nutrition -
Auto means self and trophos means nourishment. Plants are called autotrophs
because they make their food themselves. The making of food for themselves is
called the Autotrophic nutrition. Autotrophic nutrition is found in green
Heterotrophic Nutrition –
The word Heterotrophic is the combination of two words i.e. Hetero + Trophos.
Hetero means ‘others’ and ‘trophos’ means nourishment. If organisms depend on
others for their food, it is called the Hetetrophic Nutrition.
Animals cannot make their food themselves. They depend for food upon plants.
Therefore, nutrition in animals is called Hetetrophic Nutrition. Animals are
known as Heterotrophs.
Saprotrophic Nutrition –
The taking of nutrients by organism from dead and decaying matter in the form of
solution is called the saprotrophic nutrition. The organisms which use
saprotrophic mode of nutrition are called saprotrophs. For example: fungi.
Questions – 1: What is autotroph?
Answer- Organisms that make their food themselves are called autotrophs.
Question-2: What is autotrophic mode of nutrition?
Answer: The mode of nutrition in which the organism makes its own food is called
autotrophic mode of nutrition.
Question -3: Give some example of autotrophs.
Answer: All green plants, such as grass, mango, bougainvillea, etc. are the
examples of autotrophs.
Question-4: What is heterotrophic mode of nutrition?
Answer: The mode of nutrition in which an organism takes food from another
organism is called heterotrophic mode of nutrition. The nutrition in animals and
non-green plants is the example of heterotrophic mode of nutrition.
Question-5: Give examples of Heterotrophs.
Answer: Animals and non green plants are the examples of heterotrophs.
Question-6: What is saprotrophs?
Answer: Plants which get their nutrition from dead or decaying plants in liquid
form are called saprotrophs.
Photosynthesis - Food Making Process in Plants
The process of making of food by green plants in the presence of sunlight and chlorophyll is known as photosynthesis.
Photosynthesis is the combination of two words- Photo + Synthesis. ‘Photo’ means
light and ‘Synthesis’ means to make.
Process of food making in green plants:
Green plants make their food themselves. Green leaves make food from Carbon
dioxide and water in the presence of sunlight and chlorophyll.
Hence, for taking place of photosynthesis carbon dioxide, water and sunlight
must be reached at the green leaves in addition to presence of chlorophyll.
Leaves have several tiny pores like structure on its lower surface. This is
called stomata through which leaves absorb carbon dioxide from air. Water is
transported to the leaves through hair like pipelines from the roots. These
pipelines are present throughout the plant, i.e. from roots to branches and
leaves. These pipe-lines are known as Xylem. Xylem is a type of tissues. Chlorophyll,
a green pigment, is found in green leaves. Chlorophyll absorbs
sunlight and gives energy. Chlorophyll absorbs sunlight, carbon dioxide and water and convert them to carbohydrate and oxygen. Carbohydrate is used as food and oxygen is emitted out to atmosphrere.This whole process of making food by plants is called
The reaction takes place in the process of photosynthesis can be written as:
Carbohydrate which is produced in the process of photosynthesis is ultimately converted into starch and
stored into leaves. From leaves it is transported to the parts of plants. Starch
is a type of carbohydrate. The oxygen so produced is released into
atmosphere through the stomata.
Leaves are known as the kitchen or food factories of the plants because photosynthesis takes place in leaves. Leaves look green because of the
presence of chlorophyll.
Besides leaves, photosynthesis takes place in other green parts of the plant
also, such as in green stems. Chlorophyll is necessary for photosynthesis; hence
photosynthesis takes place only in green plants.
The leaves of plants that grow in desert areas are modified in spine like structure
or scales to reduce the loss of water in the course of transpiration. In such
plants photosynthesis takes place in green stems.
The photosynthesis helps to maintain a balance between oxygen and carbon dioxide
in the atmosphere as it absorbs carbon dioxide and release oxygen.
Sunlight is necessary for photosynthesis. Thus sun is
the ultimate source of energy for all living organism.
Our earth is the only unique planet, where photosynthesis takes place. In the absence of photosynthesis life would not be possible on earth.
Following are necessary for photosynthesis to be taken place:
• Presence of sunlight
• Presence of Chlorophyll
• Presence of Water
• Presence of carbon-dioxide
Photosynthesis in Algae –
Green patches in ponds or near the stagnant water can be seen easily. These
green patches are living organism called algae. Algae are plants. Often algae
grow near the shallow waterlogged areas such as near tube-wells, taps, etc. One
may slip over it. Algae look green because of presence of Chlorophyll. Algae
prepare their own food by the process of photosynthesis.
Questions- 1 - What is photosynthesis?
Answer- The process of making food in green plants in the presence of sunlight
is known as photosynthesis.
Questions- 2 - What are the essentials factors for the photosynthesis?
Answer - Carbon dioxide, water, chlorophyll and sunlight are essentials factors
for the photosynthesis to take place.
Question – 3 - What is chlorophyll?
Answer- Chlorophyll is the green pigment present in green leaves.
Question – 4 – Why do leaves look green?
Answer – Leaves look green because of the presence of chlorophyll, which is a
Questions- 5: What is the function of chlorophyll?
Answer - Chlorophyll absorbs the sunlight for photosynthesis.
Question – 6: What are the final products made after photosynthesis?
Answer- Glucose and oxygen are the final products after photosynthesis.
Questions – 7: What are stomata?
Answer- The small pores present on the lower surface of leaf, are called
Questions- 8: What is function of stomata?
Answer - Stomata absorb carbon dioxide from air for photosynthesis.
Question - 9: What is the ultimate source of energy?
Answer – Sun is the ultimate source of energy.
Question – 10: How water is transported to the leaves?
Answer: Water is transported to the leaves through pipe like structures from the
roots of plant. These pipe-like structures are present from root to leaves
through branches throughout.
Synthesis of plant food other than carbohydrate
Plants need proteins and fats besides the carbohydrate. Proteins are nitrogenous
substances which contain nitrogen. Although nitrogen is present in abundance in
atmosphere, but plant cannot absorb atmospheric nitrogen. Plant gets nitrogen
from soil. Certain types of bacteria called rhizobium, are present in soil. They
convert gaseous nitrogen into usable form and release it into the soil. Plants
absorb these soluble forms of nitrogen along with water and other minerals
through their roots.
Sometimes farmers add nitrogenous fertilizer to their field to fulfill the need
of nitrogen. In this way plants gets fulfillment of nitrogen along with other
nutrients. After the fulfillment of all nutrients plants synthesise proteins and
Question: 1 – What are the nutrients other than carbohydrates which are required
Answer: Proteins and fats are the nutrients; other than carbohydrates; which are
required by plants.
Question: 2 – In which form do plants absorb nitrogen?
Answer: Plants absorb soluble form of nitrogen.
Question: 3 – Why do farmers add nitrogenous fertilizers to the soil?
Answer: Farmers add nitrogenous fertilizers to the soil to fulfill the
requirement of nitrogen of the plants. Nitrogen is necessary to synthesise
Question: 4 – Which microorganism help to provide nitrogen to the plants?
Answer: A certain type of bacteria called rhizobium help to provide nitrogen to
Question: 5 – How do plants absorb nutrients other than carbohydrates from the
Answer: Other nutrients are available in the soil in the form of minerals.
Plants absorb these minerals from the soil; along with water.
MODES OF NUTRITION IN NON GREEN PLANTS - HETEROTROPHIC MODE OF NUTRITION IN
Some plants do not have the chlorophyll. Hence, they cannot synthesise their
food by themselves. Such plants are known as non green plants. They depend on
other organisms for food. Such plants use the heterotrophic mode of nutrition.
Some of them are called parasite. A parasite is an organism which lives on or
inside the body of another organism and takes shelter and food from that
organism. The host; in this case; is always at loss.
Plants that do not have chlorophyll are called non-green plants. Plants, which
live on other plants for food, are called parasitic plants.
Parasite (Parasitic Plant):
Plants that get their food from other plants by living on them are called
parasite. Example; Cuscuta, mistletoe.
Cuscuta is a vine like plant with yellowish stem. It twines around big trees,
like banyan tree. Cuscuta gets nutrition from the tree on which it lives. The
tree upon which it climbs and lives is called the host. Here, banyan is the host
and cuscuta is the parasite.
Some plants are total parasite while some are partial parasite.
A total parasite fully depends on other plants for their nutrition. For example
Partial parasite -
Partial parasite is a parasite that receives a part of its nutrients from host.
For example; mistletoe bears green leaves. It synthesises its own food, but
receives water and mineral from host plant.
Question: 1 – What do you understand by parasitic plants?
Answer: A plant which lives on another plant and takes nutrients is called a
Question: 2 – Give some example of parasitic plants.
Answer: Cuscuta and mistletoe
Question: 3 – Why some plants are called parasites?
Answer: Some plants are unable to prepare their own food and need to take food
from another plant. Hence, they are called parasites.
Question: 4 – What is the mode of nutrition in non-green plants?
Answer: Non-green plants show heterotrophic mode of nutrition.
Question: 5 – What do you understand by non-green plants?
Answer: A plant which lacks chlorophyll is called non-green plant.
Question: 6 – What do you understand by host?
Answer: An organism which provides shelter and nutrition to another organism is
called a host.
Question: 7 – What is partial parasite?
Answer: A parasite which depends for some of the nutrients; on another organism;
is called a partial parasite.
Question: 8 – Give example of partial parasitic plants?
Insectivorous plant –
Some plants eat insects. Such plants are called insectivorous plants. They trap
and digest the insects. Pitcher plant is the example of an insectivorous plant.
In pitcher plant the leaf is modified to form a pitcher like structure. The
bright colour of the pitcher makes it very attractive to insects. Inside the
pitcher; there are several hair-like structures. These hairs direct the trapped
insects downwards. When an insect sits on the pitcher of the plant, the lid
closes and the insects get trapped inside the pitcher. The insect is then
digested by the enzymes secreted by the cells of the plants.
Cause of eating of insects by plants: The soil of marshy land is deficient in nitrogen. Plants living in marshy areas
do not get nitrogen from the soil. Their nitrogen need is fulfilled by sucking
the juice of insects. Venus flytrap, utricularia, drosera and Rafflesia are the
other examples of insectivorous plants.
Question: 1 – What is an insectivorous plant?
Answer: A plant which fulfills its nitrogenous needs by eating insects is called an
Question: 2 – Give an example of insectivores plant?
Answer: Pitcher plant, Venus Fly trap, Bladderwort, Drosera, Rafflesia
Question: 4 – Why does a plant eat insects?
Answer: Plants living in marshy areas do not get nitrogen from the soil. To
fulfill their nitrogenous need, they need to eat insects.
Question: 5 – Write a brief note on pitcher plants?
Answer: In a pitcher plant, the leaf is modified into a pitcher like structure.
The pitcher is complete with a lid. The inside of pitcher is full of hair-like
structures. The pitcher is used to trap insects which may fall in it.
Saprtrophs are non-green plants e.g. Agaricus (Mushroom) fungi, yeasts and
bacteria. Saprotrophs get their food from dead or decaying organic matters. They
grow on decaying organic matters such as cow-dung, wood, bread, etc.
Saprotrophs secrete digestive
juice over the decaying materials and absorb nutrients from them. This is called
Saprotrophic Mode of Nutrition. Such plants are called saprotophs.
Question: 1 – What do you understand by saprotrophs?
Answer: An organism which feed on dead and decaying material is called a
saprotroph. In this mode of nutrition, digestive enzymes are secreted on the
food. The digested food is then absorbed by the organism. In saprotrophs
digestion takes place outside the body of the organism.
Question: 2 – Saprophytes grow in which type of places?
Answer: Saprophytes grow in humid and hot conditions.
Question: 3 – Give some example of saptrotrophs.
Answer: Mushroom, yeast, toadstool, etc.
Symbiosis or mutualism –
Symbiosis is the combination of two Greek words ‘Sym’ menas ‘with’ and ‘biosis’
means ‘living’, which means living together. In symbiosis or mutualism two
different types of organisms live and work together for their mutual benefit
from each other. They share shelter and nutrients, e.g. Lichens. Lichens are
composite organisms composed of fungus and alga. Fungus is a saprophyte and alga
is an autotroph. The Fungus supplies water and minerals to the cells of the alga
while the alga supplies food; prepared by photosynthesis.
A bird sitting on the back of a rhino is an example of symbiosis. The bird
gets worms to eat, while the rhino gets rid of those worms.
Replenishment of Nutrients in Soil -
Some fungus live in the roots of the plans. Roots of the plants provide shelter
and food to the fungus while fungus provides important nutrients to the plants.
Because of continuous farming nutrients keep declining in the soil. Hence, to
replenish those nutrients fertilizers are added to the soil.
Plants require a lot of nitrogen to grow and to be healthy. Although, a lot of
nitrogen is available in the atmosphere, but plants cannot absorb nitrogen in
gaseous form. There is a bacterium called Rhizobium, which lives in the root
nodules of legumes, such as gram, moong, etc. These bacteria can absorb nitrogen
from the atmosphere and make it available for the plants. Rhizobium cannot make
its food, hence, it provides nitrogen to the legumes and in return legumes
provide them food and shelter. This is an example of symbiotic relationship.
This has great importance for farmers. Fields in which leguminous plants are
grown from time to time, do not need addition of nitrogenous fertilizers.
Question: 1 – What is the meaning of word ‘Symbiosis’?
Answer: It is a relationship between two organisms in which both the organisms
benefit each other.
Question: 2 – What is Lichen?
Answer: The lichen is a composite organism formed because of symbiosis of algae
Question: 3 – Give an example of symbiotic relationship.
Answer: A small bird; called plover; cleans the crocodile’s teeth. The crocodile
keeps its mouth open and the bird takes out meat fibres stuck between the teeth.
The bird gets food in lieu of providing dentist’s services to the crocodile.
Question: 4 – How do nutrients get replenished in the soil?
Answer: There are two main means through which nutrients get replenished in the
soil. One of them is the nitrogen fixation in soil. Nitrogen fixation
replenishes nitrogenous nutrients in the soil. Another mean is decomposition of
dead remains of plants and animals (or farm waste). Decomposition of dead
remains replenishes various other nutrients in the soil.
Question: 5 – What is Rhizobium?
Answer: Rhizobium is a bacterium.
Question: 6 – What is the function of Rhizobium?
Answer: Rhizobium helps leguminous plants in nitrogen fixation in soil.
Question: 7 – How does Rhizobium help farmers?
Answer: By helping in nitrogen fixation, rhizobium increases soil fertility and
thus helps farmers.
Question: 8 – Why do farmers prefer to sow leguminous plants?
Answer: Leguminous plants carry out nitrogen fixation in soil and thus improve
Question: 9 – In which form do plants absorb nitrogen?
Answer: Plants absorb nitrogen in the form of nitrates.