Nodules

Definition

Nodules are specialized structures formed on the roots of certain plants, particularly legumes, where symbiotic nitrogen-fixing bacteria reside. These bacteria convert atmospheric nitrogen into a form that plants can readily use for growth and development.

5 Must Know Facts For Your Next Test

1. Nodules primarily form on leguminous plants such as beans, peas, and clover.
2. The most common bacteria found in nodules are from the genus Rhizobium.
3. Nodules facilitate a mutualistic relationship where plants provide carbohydrates to bacteria in exchange for fixed nitrogen.
4. These structures are critical for soil fertility as they enrich the soil with bioavailable nitrogen.
5. Nodule formation is induced by signaling molecules called Nod factors produced by the symbiotic bacteria.

Review Questions

• What type of plant structure houses nitrogen-fixing bacteria?
• Which genus of bacteria is most commonly associated with root nodules?
• How do nodules contribute to soil fertility?

Related terms

Rhizobium: A genus of bacteria that forms symbiotic relationships with legumes to fix atmospheric nitrogen within root nodules.

Nitrogen Fixation: The process by which atmospheric nitrogen is converted into ammonia or related compounds usable by plants.

Legumes: A family of plants known for their ability to form symbiotic relationships with nitrogen-fixing bacteria in their root nodules.