Which structures are found on some plant roots and contain nitrogen-fixing bacteria?

Nodules are specialized structures found on the roots of certain plants, particularly legumes, that house nitrogen-fixing bacteria. This mutually beneficial relationship allows plants to convert atmospheric nitrogen into forms that they can use for growth. The bacteria, commonly from the genus Rhizobium, reside within these nodules and perform the process of nitrogen fixation, which transforms nitrogen gas from the air into ammonia, a compound that plants can absorb and utilize.

This natural process is crucial for soil fertility and supports plant health by providing them with essential nutrients that are often limited in agricultural soils. By forming these nodules, plants are able to thrive in nitrogen-poor environments, thus playing a significant role in ecosystem productivity.