Answer:
Plants absorb soil nitrogen through their root
systems in the form of amino acids, nitrate ions (NO3 -), nitrite ions (NO2 -), or ammonium ions (NH4 +). Most of the nitrogen in the cells and tissues of terrestrial animals can be traced back to the consumption of plants at some level of a food chain.
Can plants absorb nitrogen through leaves?
Plants are already known to use their leaves to absorb inorganic airborne nitrogen molecules, such as ammonia or nitrogen dioxide, and turn them into amino acids. And a relatively reactive compound called peroxyacetyl nitrate can be absorbed by leaves, although it's not clear whether plants actually use it.
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