what role does lightning play in the nitrogen cycle?

All plants require nitrogen in order to grow well.
However, the nitrogen must be in a soluble form so it can be absorbed either through the
leaves or the roots of a plant. The earth's atmosphere is about 79% nitrogen in the form
of N2 but N2 is a very stable molecule held together by three chemical bonds so it takes
a high amount of energy to break those bonds.

When
lightning discharges in  the atmosphere some of that energy breaks the nitrogen-nitrogen
bonds and converts the nitrogen to various nitrogen-oxygen compounds.  These compounds
are water soluble and are carried down to the ground with rain water to nourish the
plants.