Question

label a diagram showing: nitrogen fixation, nitrification, assimilation, ammonification, denitrification

1. what organisms are responsible for nitrogen fixation?
2. how do plants get nitrogen?
3. what happens during denitrification?

Explanation:

1. Nitrogen - fixing bacteria (such as Rhizobium in root nodules of legumes) and some cyanobacteria convert atmospheric nitrogen into ammonia or other nitrogen - containing compounds.
2. Plants get nitrogen by absorbing nitrate ($NO_3^-$), ammonium ($NH_4^+$) ions from the soil. These ions are produced through nitrogen - fixing, nitrification, and ammonification processes.
3. During denitrification, nitrate ($NO_3^-$) is reduced to nitrogen gas ($N_2$) or nitrous oxide ($N_2O$) by denitrifying bacteria in anaerobic conditions, returning nitrogen to the atmosphere.

Answer:

1. Nitrogen - fixing bacteria and some cyanobacteria.
2. By absorbing nitrate and ammonium ions from the soil.
3. Nitrate is reduced to nitrogen gas or nitrous oxide by denitrifying bacteria in anaerobic conditions.