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Questions Related to a seeds tells a farmer's story

Leguminous plants are able to fix atmospheric nitrogen through the process ofsymbiotic nitrogen fixation. Which one of the following statements is not correct for this process of nitrogen fixation?

evs a seeds tells a farmer's story manure manures and fertilisers water absorption organ

  1. Leghaemoglobin scavenges oxygen and is pinkish in colour.

  2. Nodules act as sites for nitrogen fixation.

  3. The enzyme nitrogenase catalyses the conversion of atmospheric $N _2$ to $NH _3$.

  4. Nitrogenase is insensitive to oxygen.

Show answer
Correct Option: D

Which of the following can differentiate chemical fertlizers from natural fertilizers?

evs a seeds tells a farmer's story manure manures and fertilisers water absorption organ

  1. Chemical fertilizer is soluble but not natural fertilizer.

  2. Natural fertilizer is nutrient specific but not chemical fertilizer.

  3. Chemical fertilisers can affect the pH of the soil while natural fertilisers do not affect the pH of the soil.

  4. Both A and C

Show answer
Correct Option: D
Explanation:

  • Those fertilizers which get decomposed naturally are known as natural fertilizers whereas those which are human-made are known as chemical fertilizers. 
  • Natural fertilizers include compost, animal waste, dead organisms, etc. Chemical fertilizers include inorganic materials. 
  • Chemical fertilizers are directly available whereas natural fertilizers need to be prepared. Chemical fertilizers contain different chemical so they affect the pH value of soil whereas natural fertilizers don't.

So, the correct option is 'Both A and C'.

Leguminous plants are important in agriculture because

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  1. They are disease resistant

  2. They have high amounts of proteins

  3. They require less nitrogen for growth

  4. Nitrogen fixing bacteria are symbiotically associated in them

Show answer
Correct Option: D
Explanation:
Leguminous plants are important in agriculture because they contribute to nitrogen fixation. They contain symbiotic nitrogen-fixing bacteria within the nodules that produce nitrogen compounds that help the plant to grow. When the plant dies, the fixed nitrogen is released, making it available to other plants and this helps to fertilize the soil.
So the correct answer is 'Nitrogen-fixing bacteria are symbiotically associated in them'.

Leghaemoglobin is

evs a seeds tells a farmer's story manure manures and fertilisers water absorption organ

  1. Respiratory pigment supplying oxygen to animal legs

  2. Haemoglobin of annelids

  3. Nitrogen fixing pigment

  4. None of the above

Show answer
Correct Option: D
Explanation:
Leghaemoglobin is a protein pigment present in the nodule roots that are inhabited by Rhizobium. It acts as an oxygen scavenger and prevent the enzyme nitrogenase(which is highly sensitive to oxygen) from oxygen molecules and help it in its protection.
So the correct answer is 'None of the above'.

The pigment protein present in nodulated roots inhabited by Rhizobium is

evs a seeds tells a farmer's story manure manures and fertilisers water absorption organ

  1. Nitrate reductase

  2. Hydrogenase

  3. Leghaemoglobin

  4. Plastocyanin

Show answer
Correct Option: C
Explanation:
Rhizobium is symbiotic nitrogen-fixing bacteria present in the roots of leguminous plants. This bacteria is responsible for the formation of root nodules in legumes roots. The nodule contains a biochemical pigment protein called leg-haemoglobin that function as an oxygen scavenger.
so the correct answer is 'Leghaemoglobin'.

Function of leghaemoglobin during biological nitrogen fixation in root nodules of legumes is to

evs a seeds tells a farmer's story manure manures and fertilisers water absorption organ

  1. Convert atmospheric nitrogen to ammonia

  2. Convert ammonia to nitrite

  3. Transport oxygen for activity of nitrogenase

  4. Protect nitrogenase from oxygen

Show answer
Correct Option: D
Explanation:
Root nodules of a leguminous plant contain all the biochemical components required for nitrogen fixation including enzymes nitrogenase and a pink-coloured pigment called leghaemoglobin. Nitrogenase is highly sensitive enzyme to molecular oxygen as it functions under anaerobic conditions. To protect this enzyme from oxygen leghaemoglobin act as an oxygen scavenger.
So the correct answer is 'Protect nitrogenase from oxygen'.


The pigments essential for $N _2$ fixation by leguminous plants is leghaemogiobin

evs a seeds tells a farmer's story manure manures and fertilisers water absorption organ

  1. True

  2. False

Show answer
Correct Option: A
Explanation:
  • Leghaemoglobin is an oxygen carrier and hemoprotein found in the nitrogen-fixing root nodules of leguminous plants. 
  • Leghaemoglobin reduce the amount of free oxygen, and thereby to protect the nitrogen-fixing enzyme nitrogenase, which is irreversibly inactivated by oxygen.
  • Hence The pigments essential for $N _2$ fixation by leguminous plants is leghaemoglobin is a true statement.
  • So, the correct answer is 'True'.

Which one is correct about the free living Rhizobium sp. and its enzyme?

evs a seeds tells a farmer's story manure manures and fertilisers water absorption organ

  1. Bacteria are aerobic and nitrogenase are active

  2. Bacterial are anaerobic and nitrogenase is active (operational)

  3. Bacteria aerobic and nitrogenase is inactive

  4. Bacteria are anaerobic and nitrogenase is inactive

Show answer
Correct Option: A
Explanation:

Rhizobium, is a rod shaped, aerobic, nitrogen fixing bacterium present in the root nodules of leguminous plants. It performs symbiotic nitrogen fixation in the root nodules of leguminous plants, in presence of an enzyme dinitrogenase.

So, the correct option is ‘bacteria are aerobic and nitrogenase are active’.