Question

The conversion of N₂ gas to form nitrogen that can be used by plants is called

• A. Nitrogen fixation
• B. Nitrogen assimilation
• C. Nitrogen cycling
• D. Nitrogen uptake

Answer 1

The correct option is A

Nitrogen fixation

The correct option is A

The explanation for the correct option:

1. Nitrogen fixation is the process of turning N₂ into physiologically accessible nitrogen.
2. Because of the strength of the triple bond between nitrogen atoms, N₂ gas is a very stable chemical that takes a lot of energy to break.
3. N₂ must be converted before it can be used by plants, a process is known as nitrogen fixation.
4. Fixation transforms atmospheric nitrogen into forms that plants may receive through their roots.

The explanation for incorrect options:

Option B:

1. The process through which plants and animals assimilate NO₃- and ammonia produced by nitrogen fixation and nitrification is known as assimilation.
2. These types of nitrogen are taken up by plants through their roots and incorporated into plant proteins and nucleic acids.

Option C:

1. The nitrogen cycle is a biogeochemical cycle in which nitrogen is transformed into numerous chemical forms as it moves through the atmospheric, land, and sea ecosystems.
2. Nitrogen conversion can be accomplished by biological and physical processes.

Option D:

1. Plants acquire nitrogen as both NH4+ and NO3 ions from the soil, but because nitrification is so widespread in agricultural soils, the majority of nitrogen is taken up as nitrate.
2. As plant roots absorb water, nitrate travels freely toward them.

Final Answer: The conversion of N₂ gas to form nitrogen that can be used by plants is called nitrogen fixation.