Question

If by radiation all nitrogenase enzymes are inactivated, then there will be no

• A. fixation of atmospheric nitrogen
• B. conversion from nitrate to nitrite in legumes
• C. conversion from ammonium to nitrate in soil
• D. fixation of nitrogen in legumes

Answer 1

The correct option is (A):

Explanation of the correct option:

1. Nitrogenases are enzymes that are produced by certain bacteria.
   
2. These enzymes are responsible for the reduction of nitrogen $\left(N_2\right)$ to ammonia $\left(N{H}_3\right)$.
   
3. Nitrogenases are the only family of enzymes known to catalyze this reaction, which is a key step in the process of nitrogen fixation.
   
4. Therefore, if all nitrogenases are deactivated by radiation, there will be no nitrogen fixation and in turn, it will affect all the life forms on the earth too.

Explanation of the incorrect options:

Option (B):

1. ​The nitrogenase enzyme is not required for the conversion of nitrate to nitrite and hence it is not affected.
   

Option (C):

1. Conversion of ammonium to nitrate does not occur in the presence of nitrogenase.

Option (D):

1. The Rhizobium present in the roots of the leguminous plants directly trap the nitrogen for the plants and are not affected due to radiation as it does not need nitrgenase.

Final Answer: If by radiation all nitrogenase enzymes are inactivated, then there will be no fixation of atmospheric nitrogen.