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  • Which of the following form of nitrogen is directly absorbed by the plants?Option: 1 DinitrogenOption:

Which of the following form of nitrogen is directly absorbed by the plants?

Option: 1

Dinitrogen


Option: 2

Ammonia


Option: 3

Nitrate


Option: 4

Both a and b


Answers (1)

best_answer

 

1. Ammonification

  • Ammonification is a process in which the organic nitrogen of plants and animals after their death is converted to ammonium ions (NH4) by the action of saprotrophic fungi and bacteria. 
  • The saprotrophs use ammonia (NH3) to synthesize their own proteins and other nitrogen-containing organic compounds.

2. Nitrification:

  • Ammonium ions added to the soil by ammonification, are soon oxidized by a process known as nitrification. 
  • It takes place in two stages. 
  • In the first stage, ammonium (NH4+) is converted to nitrite (NO2-). 
  • This reaction involves the addition of oxygen to ammonia, giving rise to hydroxylamine (NH2OH), which is further oxidized to nitrite. 
  • This reaction is completed by bacteria such as  
  • The second stage of nitrification involves the oxidation of nitrite (NO2) to nitrate (NO3) by bacteria like Nitrobacter, Nitrospira and Nitrococcus. 
  • The reaction proceeds by the addition of water followed by the removal of hydrogen.

TIP: 

  • Nitrate (NO3–) formed in the process of nitrification is used by most plants as a mineral metabolite and may be converted by them into amino groups and other nitrogen-containing compounds. 
  • Nitrates are also added to the soil through rock dissolution and a combination of atmospheric nitrogen with oxygen by lightning (nitrates so formed reach the soil by rain).
  • However, many plants also absorb ammonia from the soil.

3. Denitrification:

  • It is a process in which the nitrate ion (NO3) is reduced to nitrogen dioxide (NO2), di-nitrogen oxide (N2O), nitrogen monoxide (NO) or nitrogen (N2) by certain soil bacteria like Pseudomonas denitrificans. 
  • Thus, nitrogen is liberated into the atmosphere. 
  • Plants also lose small amounts of nitrogen to the atmosphere as gaseous ammonia, N2O, NO2 and NO especially when well fertilized with nitrogen

 

Hence, the correct answer is option d.

Posted by

Ritika Jonwal

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