28.Which one of the following produces nitrogen fixing nodules on the roots of Alnus? A. Frankia B. Rhodospirillum C. Beijernickia D. Rhizobium
Option A Several bacteria produce small outgrowths (spherical) on the surface of legume roots, called as nodules. Rhizobium produces nitrogen fixing nodules in leguminous plants. But, Frankia also produces nitrogen-fixing nodules on the roots of non-leguminous plants (e.g. Alnus). Frankia is free-living in the soil, but can fix atmospheric nitogen as symbionts.
