Download Nutrition in Plants

CHAPTER
Nutrition in Plants
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POINTS TO REMEMBER
1. All organisms take food and utilize it to get energy for the growth and maintenance
of their bodies.
2. The taking of food by an organism and its utilization by the body is called nutrition.
3. There are four main types of modes of nutrition:
• Autotrophic
• Heterotrophic
• Saprotrophic
• Parasitic
4. Autotrophic mode of Nutrition:
• Green plants synthesize their food themselves by the process of photosynthesis.
They are autotrophs.
• During photosynthesis chlorophyll containing cells of leaves in the presence of
sunlight, use carbon dioxide and water to synthesize carbohydrate.
Carbon dioxide + Water
Sunlight
→ Carbohydrate + Water + Oxygen
Chlorophyll
• Oxygen released in the photosynthesis is utilized by living organisms for their
survival.
5. Heterotrophic mode of Nutrition:
• Fungi derive nutrition from dead, decaying matter. They are Saprotrophs.
• Plants like cascula are parasites. They take food from the host plant.
• A few plants and all animals are dependent on others for their nutrition and are
called Heterotrophs.
KEY WORDS
1. Autotrophic: The mode of nutrition in which organisms make food themselves
from simple substances is called autotrophic (auto = self, trophos = nourishment)
nutrition. Therefore, green plants are called autotrophs.
2. Chlorophyll: A green plant pigment which absorb energy from sunlight, enabling
the plant to build up food as carbohydrates from carbon dioxide and water by
photosynthesis.
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GOLDEN SCIENCE—VII
3. Heterotrophs: The category of organisms that take readymade food prepared by
the plants are called heterotrophs (heteros = other, trophos = nourishment), example:
human, animals, etc.
4. Host: A plant or an animal that supports a parasite is called host.
5. Insectivorous: Some plants trap the insects and eat it that come in their contact.
Such insect eating plants are called insectivorous plants, e.g., pitcher plant.
6. Nutrients: Carbohydrates, proteins, fats, vitamins and minerals are the components
of food. These components of food are necessary for our body and are called nutrients.
7. Nutrition: It is the mode of taking food by an organism and its utilization by the
body.
8. Parasites: Some plants take readymade food from other organisms and harms
them. Such plants are called parasites and the organism, that suffers are called
host, e.g., cuscuta is a parasite.
9. Photosynthesis:
(i) It is food making process in plants.
(ii) The synthesis of food in plants occurs in all the green parts of it, especially
leaves.
10. Saprotrophs: The category of organisms that take nutrients from dead and
decaying matter are called saprotrophs.
11. Saprotrophic: The mode of neutrition is which an organism takes its food from
dead and decaying matter.
12. Stomata: These are the tiny pores present on the surface of the leaves. These
pores are surrounded by ‘guard cells’. Such pores are called stomata.
NCERT TEXTBOOK EXERCISES
Q. 1. Why do organisms need to take food?
Ans. Food is needed by all living species for the following purposes:
(a) It is meant for the general growth and development of an organism. If it is not
in sufficient amount, then it shows insufficient growth and development.
(b) It is meant to provide energy. We need energy for movements such as running,
walking or raising our arm.
(c) It is also needed by living beings for repairing of their damaged parts.
(d) It gives us resistance against diseases and protects us from infections.
Q. 2. Distinguish between a parasite and a saprotroph.
Ans.
Parasite
Saprotroph
1. A parasite takes the food from the organism
on which it lives.
1. They secrete digestive juices on the matter
they live and convert it into a solution and
then absorb it.
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NUTRITION IN PLANTS
2. They feed on a living organism.
2. They feed on dead and decaying organism.
3. The organism on which it feeds is called
host.
3. They do not feed on a living organism.
4. It deprives the host of valuable nutrients.
4. There is no host at all.
Q. 3. How would you test the presence of starch in leaves?
Ans. Presence of starch in leaves can be tested by Iodine Test. Iodine turns starch
solution into blue-black colour.
Q. 4. Give a brief description of the process of synthesis of food in green plants.
Ans. Leaves of a plant have a green pigment called chlorophyll. In the presence of
sunlight, they use carbon dioxide and water to synthesise carbohydrate.
Carbon dioxide + Water
Sunlight
→ Carbohydrate + Water + Oxygen
Chlorophyll
During the process oxygen is released. The carbohydrates ultimately get converted
into starch.
Carbon dioxide from air is taken through stomata. Water and minerals are absorbed
by the roots and transported to leaves.
Q. 5. Show with the help of a sketch that the plants are the ultimate source of food.
Ans.
SUN
Solar energy
PLANTS
(Producer)
and Autotrophs
On death and decay
HERBIVORES
(Consumer)
and heterotrophs
CARNIVORES
(Consumer)
and heterotrophs
DECOMPOSERS
Fig. 1.1. Plants capture solar energy by a unique process called photosynthesis
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GOLDEN SCIENCE—VII
Q. 6. Fill in the blanks:
(a) Green plants are called ...................... since they synthesise their own food.
(b) The food synthesised by the plants is stored as .......................... .
(c) In photosynthesis solar energy is captured by the pigment called ................... .
(d) During photosynthesis plants take in .................. and release ................... .
Ans. (a) autotrophs
(b) starch
(c) chlorophyll
(d) carbon dioxide, oxygen
Q. 7. Name the following:
(i) A parasitic plant with yellow, slender and tubular stem.
(ii) A plant that has both autotrophic and heterotrophic mode of nutrition.
(iii) The pores through which leaves exchange gases.
Ans.
(i) Cuscuta
(ii) Insectivorous plants
(iii) Stomata.
Q. 8. Tick the correct answer:
(a) Amarbel is an example of
(i) autotroph
(ii) parasite
(iii) saprotroph
(iv) host
(b) The plant which traps and feeds on insects is
(i) Cuscuta
(ii) China rose
(iii) Pitcher plant
(iv) Rose
Ans. (a) (ii) Parasite
(b) (iii) Pitcher plant.
Q. 9. Match the items given in Column I with those in Column II:
Column I
Column II
(i) Chlorophyll
Bacteria
(ii) Nitrogen
Heterotrophs
(iii) Amarbel
Pitcher plant
(iv) Animals
Leaf
(v) Insects
Parasite
Ans. Column I
Column II
(i) Chlorophyll
Leaf
(ii) Nitrogen
Bacteria
(iii) Amarbel
Parasite
(iv) Animals
Heterotrophs
(v) Insects
Pitcher plant
Q. 10. Mark ‘T’ if the statement is true and ‘F’ if it is false:
(i) Carbon dioxide is released during photosynthesis.
(T/F)
(ii) Plants which synthesise their food themselves are called saprotrophs. (T/F)
(iii) The product of photosynthesis is not a protein.
(T/F)
(iv) Solar energy is converted into chemical energy during photosynthesis. (T/F)
Ans.
(i) F
(ii) F
(iii) T
(iv) T.
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NUTRITION IN PLANTS
Q. 11. Choose the correct option from the following:
Which part of the plant takes in carbon dioxide from the air for
photosynthesis?
(i) Root hair
(iii) Leaf veins
(ii) Stomata
(iv) Sepals
Ans. (ii) Stomata.
Q. 12. Choose the correct option from the following:
Plants take carbon dioxide from the atmosphere mainly through their:
(i) roots
(ii) stem
(iii) flowers
(iv) leaves
Ans. (iv) Leaves.
ADDITIONAL IMPORTANT QUESTIONS
1.1 MODE OF NUTRITION IN PLANTS
Q. 1. What is nutrition?
Ans. Nutrition is the mode of taking food by an organism and its utilization by the body.
Q. 2. Name various mode of nutrition.
Ans. Various modes of nutrition are:
(i) autotrophic nutrition.
(ii) heterotrophic nutrition.
(iii) saprotrophic nutrition.
Q. 3. Why the plants are called autotrophs?
Ans. Plants can make their own food from simple substances. Therefore, plants are
called autotrophs.
Q. 4. What is the ultimate source of energy for all living organisms?
Ans. The sun is the ultimate source of energy for all living organisms.
1.2 PHOTOSYNTHESIS—FOOD MAKING PROCESS IN PLANTS
Q. 1. Why the leaves are generally green?
Ans. Leaves are generally green because they contain a green pigment called chlorophyll.
Q. 2. Food making process in plants is called photosynthesis. In which part of the
plant does photosynthesis occur?
Ans. Photosynthesis occurs in leaves.
Q. 3. What are stomata?
Ans. These are the tiny pores present on the surface of leaves.
Q. 4. Why the food making process in plants is called photosynthesis?
Ans. The chlorophyll present in the leaves of the green plants help them to capture the
solar energy. This energy is used to synthesise food from carbon dioxide and water. Since the
synthesis of food occurs in sunlight, it is called photosynthesis (Photo: light, synthesis: to
combine).
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GOLDEN SCIENCE—VII
Q. 5. “In the absence of photosynthesis, life is impossible on the earth”. Explain.
Ans. In the absence of green plants there would not be the process of photosynthesis.
The survival of almost all living organisms directly or indirectly depends upon the food made
by the plants. Besides oxygen it is an example of interspecific interaction in which both the
partners are benefitted which is essential for the survival of all living organisms is produced
during photosynthesis. Thus, we can say that life would be impossible on the earth in the
absence of photosynthesis.
Q. 6. What is autotrophic mode of nutrition? How plants prepare their own
food?
Ans. Autotrophic mode of nutrition. The mode of nutrition in which organisms
make food themselves from simple substances is called autotrophic (auto = self, trophos =
nourishment) nutrition. Therefore, plants are called autotrophs.
Photosynthesis—Food making process in plants. The synthesis of food in plants
takes place in leaves. Therefore all the raw materials must reach there. Water and minerals
present in the soil are absorbed by roots and transported to leaves through stems. Carbon
dioxide from air is taken in through the tiny pores present on the surface of leaves called
stomata.
The leaves have a green pigment called chlorophyll. It helps leaves to capture the solar
energy. This energy is used to synthesise food by the process called photosynthesis.
During photosynthesis, chlorophyll containing cells of leaves (Fig. 1.2) in the presence
of sunlight, using carbon dioxide and water to synthesise carbohydrates. The process can be
represented as an equation:
Carbon dioxide + Water
Sunlight
→ Carbohydrate + Water + Oxygen
Chlorophyll
During this process oxygen is released. The carbohydrate ultimately get converted into
starch.
Light energy
Sun
Carbon
dioxide
Oxygen
Chlorophyll in
leaf
Water and
minerals
Fig. 1.2. Schematic diagram showing photosynthesis
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NUTRITION IN PLANTS
1.3 OTHER MODES OF NUTRITION IN PLANTS
Q. 1. Why insectivorous plants eat insects?
Ans. To fulfil their needs of nitrogen.
Q. 2. Why the parasites are named so?
Ans. They are called parasites because they deprive the host’s valuable nutrients and
harm the host by causing diseases.
Q. 3. What are lichens?
Ans. Lichens are organisms in which an alga and a fungus live together. The fungus
provides shelter, water and minerals to the alga and in return, alga provides food which it
prepares by photosynthesis.
Q. 4. What is symbiotic relationship?
Ans. Some organisms live together and share shelter and nutrients and mutually
benefitted. This is called symbiotic relationship.
Q. 5. “All animals depend upon the plants for food.” Justify the statement.
Ans. We know that the source of energy for living organisms is food. All green plants
form the major part of food by simple inorganic substances like carbon dioxide and water in
the presence of sunlight and chlorophyll. This is known as autotrophic (holophytic) nutrition.
But in case of animals they cannot synthesise their food themselves. So all animals depend
on the green plants for food.
Q. 6. Distinguish between an autotroph and a heterotroph.
Ans.
Autotroph
Heterotroph
1. They are capable of synthesising their own
food.
1. They cannot manufacture their own food.
2. They form the first trophic level of any food
chain.
2. They form the higher levels in any food chain.
3. They usually contain chlorophyll.
3. Chlorophyll are absent in them.
Q. 7. Discuss in brief about the mechanism of eating insects by pitcher plant.
Ans.
Lid
Leaf modified into pitcher
Fig. 1.3. Pitcher plant showing lid and pitcher
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GOLDEN SCIENCE—VII
Pitcher plant: In insectivorous plant leaves are modified into a pitcher like structure.
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 downwardly directed. When an insect lands in the
pitcher, it slips inside and the lid closes. The trapped insect is entangled into the hair. The
insect is digested by the digestive juices secreted in the pitcher.
Q. 8. What are parasites? Explain by taking the example of Cuscuta (Amarbel).
Ans.
Fig. 1.4. Cuscuta (Amarbel) on host plant
Cuscuta is a plant which looks like yellow thread like structures twining around the
stem and branches of some trees (Fig. 1.4).
It lacks chlorophyll but takes readymade food from the host plant. The plant on which
it climbs is called a host. Since it deprives the host’s valuable nutrients, it is called a
parasite.
1.4. SAPROTROPHS
Q. 1. What are saprotrophs?
Ans. Organisms which take the nutrients in the form of solution from dead and decaying
matter are called saprotrophs.
Q. 2. What is the mode of nutrition in fungi?
Ans. Fungi secrete digestive juices on the dead and decaying matter and convert it into
a solution. Then they absorb nutrients from it. This mode of nutrition in which organisms
take in nutrients in solution form from dead and decaying matter is called saprotrophic
nutrition.
1.5. HOW NUTRIENTS ARE REPLENISHED IN THE SOIL?
Q. 1. Explain why fertilizers and manures are needed to the fields from time
to time?
Ans. We know that plants absorb minerals nutrients from the soil. So their amount in
the soil keep on declining. Fertilizers and manures contain nutrients such as nitrogen,
potassium, phosphorous, etc. Therefore, to overcome the deficit of these nutrients in the soil
we need to add these fertilizers and manures from time to time.
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Q. 2. How symbiotic bacterium called Rhizobium is important for the farmers?
Ans. Usually crops requires a lot of nitrogen. But they cannot utilize atmospheric
nitrogen. They need it in soluble form. The bacterium called Rhizobium can convert
atmospheric nitrogen into a soluble form. But Rhizobium cannot make its own food. So it
lives in the roots of gram, peas, moong, beans and other legumes and provides them nitrogen.
In return, the plant provides food and shelter to the bacteria. They have symbiotic relationship.
This association is of great importance for the farmers.
OBJECTIVE TYPE QUESTIONS
Q. 1. Match the items given in Column I with those given in Column II.
Column I
Column II
(i) Autotrophs
(a) Fungi
(ii) Heterotroph
(b) Lichen
(iii) Parasite
(c) Pitcher Plant
(iv) Saproptroph
(d) Algae
(v) Symbiont
(vi) Insectivorous
(e) Man
(f ) Cuscuta
Q. 2. Fill in the blank space in the following statements:
(i) All organisms take ................... and utilize it to get energy for the growth and the
maintenance of their bodies.
(ii) Green plants synthesise their food themselves by the process of ................... they
are called ................... .
(iii) ................... energy is stored by the leaves with the help of chlorophyll.
(iv) ................... derive nutrition from dead, decaying matter.
(v) Plants like cuscuta take food from ................... plant.
(vi) All animals are categorised as ................... .
(vii) ................... is produced and ................... is utilized during photosynthesis.
(viii) ................... is the site of reception of light energy in leaves.
Q. 3. Choose the true and false statements from the following:
(i) Food is essential for all living organisms.
(ii) Leaves are the food factories of plant.
(iii) Water comes into leaves through stomata in the form of vapours.
(iv) Plants utilize the carbon dioxide dissolved in the water absorbed by the roots for
photosynthesis.
(v) The sun is the ultimate source of energy for all living organisms.
(vi) Algae are saprotrophs.
(vii) Cuscuta is a parasite.
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GOLDEN SCIENCE—VII
(viii) Saprotrophs take their food in solution form from dead and decaying matter.
(ix) Insectivorous plants are partial heterotrophs.
(x) Plants take atmospheric nitrogen through stomata and utilize as a nutrient.
Q. 4. Choose the correct option in the following:
(i) Which of the following is a nutrient?
(a) Protein
(b) Fat
(c) Vitamins
(d) All of these
(ii) Human beings can be categorised as
(a) heterotrophs
(b) autotrophs
(c) parasites
(d) saprotrophs
(iii) The food making process in plants is called as
(a) glycolysis
(b) photosynthesis
(c) photolysis
(d) chemosynthesis
(iv) Which part of the plant is called its food factory?
(a) Fruits
(b) Seeds
(c) Leaves
(d) Flowers
(v) Tiny pores present on the surface of leaves through which gaseous exchange occurs
are called
(a) stomata
(b) guard cells
(c) food holes
(d) gas holes
(vi) What is the ultimate source of energy for all living organisms?
(a) Water energy
(b) Wind energy
(c) Solar energy
(d) Chemical energy
(vii) Green pigment present in the leaves is called
(a) haemoglobin
(b) globulin
(c) albumin
(d) chlorophyll
(viii) During photosynthesis plants
(a) take oxygen and release carbon dioxide
(b) take carbon dioxide and release oxygen
(c) take carbon dioxide but do not release oxygen
(d) take oxygen but do not release carbon dioxide
(ix) During photosynthesis
(a) solar energy is converted into chemical energy
(b) solar energy is converted into mechanical energy
(c) chemical energy is converted into mechanical energy
(d) bio energy is converted into chemical energy
(x) The raw materials for photosynthesis are
(a) CO2, water
(b) CO2, O2, H2
(c) N2, water
(d) O2, water
(a) carbohydrates, oxygen
(b) carbohydrates, hydrogen
(c) carbohydrates, water vapours
(d) carbohydrates, oxygen and water vapours
(xi) The end products of photosynthesis are