Nutrition in Plants NCERT Solutions - Science & Technology for UPSC CSE

Q1. Why do organisms take food?
Ans: Food is required by all living organisms mainly for four reasons or purposes:

• Food helps a living organism to grow. If enough food is not given or if, the food given is not of the right kind, the organism will not have proper growth.
• Another important function of food is to provide energy which is required for any living organism for movements and other activities.Food
• Food is also needed by living organisms for the replacement and repairing of their damaged parts.
• Food provides us with the power to fight against infections and diseases.
  
  

Q2. Distinguish between a parasite and a saprotroph.
Ans:

Q3. How would you test the presence of starch in leaves?
Ans: The presence of starch on leaves can be tested by the Iodine Test. Iodine turns starch solution blue.

Iodine test:

• Set up one plant on a sunny windowsill and another in a dark room for 24 hours
• After 24 hours, fill a beaker with ethyl alcohol and place it in a saucepan full of water
• Continue heating the pan until ethyl alcohol starts boiling and then take it off from the heat
• With the help of tweezers, dip each of the leaves in hot water for a minute
• Now, dip the leaves in the beaker holding ethyl alcohol for 120 seconds or till they change their colour to almost white
• Place each of them in a shallow dish
• Cover these leaves with some drops of iodine solution and observe

Observation:

• Blue-black colour will be observed on the leaves of the plant kept in sunlight, which indicates the presence of starch.
• Blue-black colour will not be observed on the leaves of plant kept in the darkroom. This indicates the absence of starch. 

Q4. Give a brief description of the process of synthesis of food in green plants.
Ans:Photosynthesis

• Leaves have a green pigment called chlorophyll. In presence of sunlight, they use carbon dioxide and water to synthesize carbohydrate. 
• During this process, oxygen is released. The carbohydrates ultimately get converted into starch. 
• Carbon dioxide from the air is taken through stomata. 
• Water and minerals are absorbed by roots and transported to leaves.

Q5. Show with the help of a sketch that the plants are the ultimate source of food.
Ans: The food chain below shows that the plant is the ultimate producer.

Food Chain

Q6. Fill in the blanks:
(a) Green plants are called __________ since they synthesise their own food.
(b) The foods synthesized by plants is stored as __________.
(c) In photosynthesis solar energy is absorbed by the pigment called _________.
(d) During photosynthesis plants take in _________ and release _________ gas.
Ans:
(a) autotrophs
(b) starch 
(c) chlorophyll 
(d) carbon dioxide, oxygen

Q7. Name the following:
(i) A parasitic plant with yellow, slender and branched stem.
Ans: Cuscuta Cuscuta
(ii) A plant that is partially autotrophic. 
Ans: Insectivorous plants (Pitcher Plant)

(iii) The pores through which leaves exchange gases.
Ans: Stomata

Q8. Tick the correct answer: 
(a) Cuscuta is an example of: 
(i) autotroph 
(ii) parasite 
(iii) saprotroph 
(iv) host
Ans: (ii) Parasite

(b) The plant which traps and feeds on insects is: 
(i) Cuscuta 
(ii) china rose 
(iii) pitcher plant 
(iv) rose
Ans: (iii) pitcher plant

Q9. Match the items in column I with those in column II:

Ans:

• Leaves have a green pigment called chlorophyll. Chlorophyll is essential in photosynthesis, allowing plants to absorb energy from light.
• Plants cannot themselves obtain their nitrogen from the air but rely mainly on the supply of combined nitrogen in the form of ammonia, or nitrates, resulting from nitrogen fixation by free-living bacteria in the soil or bacteria living symbiotically in nodules on the roots of legumes.
• Amarbel is an example of a parasite. Parasites are an incredibly varied group of organisms that live within host cells. They receive all sorts of benefits like food and shelter from the host plant.
• The animals cannot prepare their own food. Therefore, they have to rely on other plants or animals for nutrition. This is known as heterotrophic nutrition.
• The plant which traps and feeds on insects is the pitcher plant. 
  
  

Q10. Mark “T” if the statement is true and “F” if it is false.
(i) Carbon dioxide is released during photosynthesis. 
Ans: False  

(ii) Plants which synthesise their food are called saprotrophs.
Ans: False 

(iii) The product of photosynthesis is not a protein.
Ans: True
(iv) Solar energy is converted into chemical energy during photosynthesis.
Ans: True

Q11. Choose the correct option from the following:
Which part of the plant takes in carbon dioxide from the air for photosynthesis?
(a) Root hair 
(b) Stomata 
(c) Leaf veins 
(d) Petals

Correct Answer is Option (b)

• Stomata are holes made from spaces between special cells. 
• These holes are where plants absorb carbon dioxide from the air. Once inside the leaf, the carbon dioxide can enter plant cells. 
• Inside the plant, cells are special cell parts called chloroplasts, where photosynthesis takes place.

Q12. Choose the correct option from the following:
Plants take carbon dioxide from the atmosphere mainly through their:
(a) roots
(b) stem
(c) flowers 
(d) leaves

Correct Answer is Option (d)

• Atmospheric carbon dioxide enters plants mainly through the pores in the leaves called stomata during photosynthesis.
• Stomata are the small opening on the surface of the leaves.

Q13. Why do farmers grow many fruits and vegetable crops inside large greenhouses? What are the advantages to the farmers?
Ans. Fruits and vegetable crops are grown in large greenhouses because it protects crops from external climatic conditions and provides suitable temperature for the growth of crops.
Advantages to the farmers by growing fruits and vegetable crops inside large greenhouses are:

• It provides optimum sunlight, temperature and water to the crop.
• It protects crops from adverse climatic conditions.
• It also protects crops from pests, rodents and different animals. Thus, preventing crops from several diseases.