Question

Which one of the following produces nitrogen fixing nodules on the roots of Alnus?

• A. Rhizobium
• B. Frankia
• C. Rhodospirillum
• D. Beijerinckia

Answer 1

The Correct Option is B

In biological systems, nitrogen fixation is a critical process where atmospheric nitrogen is converted into a form usable by plants. Certain microorganisms form symbiotic relationships with plants, allowing for this conversion. Specifically, the roots of Alnus species, commonly known as alder trees, are notable for having symbiotic associations with nitrogen-fixing bacteria. Among the given options:

• Rhizobium: Typically forms nodules on legumes (e.g., peas, beans) but not Alnus.
• Frankia: A genus of actinobacteria known to form nitrogen-fixing nodules on non-legume plants, including the roots of Alnus.
• Rhodospirillum: A genus of purple non-sulfur bacteria that does not typically form root nodules.
• Beijerinckia: A free-living nitrogen-fixing bacterium, not associated with root nodules on Alnus.

Thus, the organism responsible for producing nitrogen-fixing nodules on Alnus is Frankia.