Plants get the nitrogen they need to create amino acids and DNA primarily from nitrogen compounds in the soil, such as nitrate (NO3^-) and ammonium (NH4^+) ions. These nitrogen forms are absorbed by the plant roots through specific transporters. Nitrogen in the soil mainly comes from the activity of nitrogen- fixing bacteria, which convert atmospheric nitrogen gas (N2), which plants cannot use directly, into ammonia and other usable forms. Plants then convert these absorbed nitrogen compounds into organic molecules like amino acids and DNA building blocks.
How Plants Acquire Nitrogen
- Plants absorb nitrogen in inorganic forms: mainly nitrate (NO3^-) and ammonium (NH4^+) ions through root transporters specialized for these ions.
- Nitrogen-fixing bacteria in the soil or in root nodules (in some plants) convert atmospheric nitrogen gas (N2) to ammonia (NH3), which is then converted to forms plants uptake.
- Plants may also absorb organic nitrogen in the form of amino acids from the soil when available.
Nitrogen Cycle Role
- Atmospheric nitrogen gas (N2) is inert and not directly usable by plants.
- Nitrogen enters the soil ecosystem via biological nitrogen fixation by bacteria, lightning, and decomposition processes.
- Soil bacteria convert organic matter into ammonium and nitrates that plants can absorb.
- Plants assimilate nitrogen into amino acids, proteins, and nucleic acids (DNA, RNA).
Thus, plants rely on nitrogen compounds produced through natural processes involving bacteria in the soil to fulfill their nitrogen needs for synthesizing amino acids and DNA.
