Root nodules are found on the roots of plants, primarily legumes, that form a symbiosis with nitrogen-fixing bacteria. Under nitrogen-limiting conditions, capable plants form a symbiotic relationship with a host-specific strain of bacteria known as rhizobia.

What are plant nodules?

Root nodules are specialized organs developed by the host plant, mostly legumes, in which the symbiotic microorganism, generally a diazotrophic bacterium, reduces N2 to ammonium.

What plants have bacteria in nodules on their roots?

Legumes are able to form a symbiotic relationship with nitrogen-fixing soil bacteria called rhizobia. The result of this symbiosis is to form nodules on the plant root, within which the bacteria can convert atmospheric nitrogen into ammonia that can be used by the plant.