Luckily, there is plenty of nitrogen in the earth s atmosphere. However, this nitrogen gas is not readily available in the form that plants can use it. The N2 gas must be converted to other forms, so that plants can use it. The conversion of nitrogen is produced in the soils that plants grow in. Bacteria, and fungi living in soil have a mutual relationship with plants as they do this conversion.
Fungi have a more interesting approach in fixing nitrogen to soils.
Plants must have nitrogen in molecules of ADP and ATP, so that there can be energy transfer during photosynthesis. Nitrogen fixation is the conversion of N2 gas into other plant useable forms. N2 has a triple bond between the two atoms. As plants roots grow and develop, fungi grow with the plants attaching themselves to the plants roots, and spreading in the soil. Mycorrhizae produce hormones that encourage plants to produce more root tips.