What is the role of legumes in the nitrogen cycle?

Legumes play a crucial role in the nitrogen cycle primarily by hosting nitrogen-fixing bacteria in root nodules. This symbiotic relationship allows legumes to convert atmospheric nitrogen gas (N2) into a form that is usable by plants, such as ammonia or nitrates. The bacteria, known as rhizobia, reside in the root nodules of legume plants and perform nitrogen fixation, enriching the soil with nitrogen compounds that can be taken up by the legume itself and also by surrounding plants.

This process is vital for maintaining soil fertility and supporting plant growth, particularly in ecosystems where nitrogen availability is limited. Additionally, when legumes die or are incorporated into the soil, the nitrogen they contain is released back into the soil, further enhancing nutrient cycling.

In contrast, the other options do not accurately reflect the primary contributions of legumes to the nitrogen cycle. For instance, while some plants can absorb nitrogen gas, it is primarily legumes that have the specialized relationship for nitrogen fixation through bacteria. The statement regarding enhancing nitrogen pollution does not align with the beneficial role legumes play in soil health, and the notion of legumes only storing nitrogen in seeds disregards their dynamic role in soil nutrient cycling. Thus, the relationship between legumes and nitrogen-fixing bacteria emphasizes their importance in