Nitrogen fixation, conceptual computer artwork. A leguminous plant is growing out of a nitrogenous molecule in the middle of an ocean. Many leguminous plants, such as peas and beans, have formed a symbiotic relationship with soil bacteria that are able to convert (fix) atmospheric nitrogen to ammonia. The plant cannot carry out this process itself, but it is vital for the production of amino acids, the building blocks of proteins. In return the plant passes carbohydrates produced during photosynthesis to the bacteria for used as an energy source.