How do plants take nitrogen from the atmosphere?

Plants absorb nitrate compounds from soil through their root hairs, which are outgrowths of the trichoblast cells in the roots.

Most plants are not able to use nitrogen as such (N2), though some, including legumes and casuarinas, supply water and food to symbiotic nitrogen-fixing bacteria in specialised root nodules, and these fix nitrogen to nitrate which they supply to the plants.