In the Legume-Rhizobium Symbiosis, Nitrogen Fixation is Carried Out in Nodules

Question

In the legume-rhizobium symbiosis, nitrogen fixation is carried out in nodules by
A) bacteroids that lack a cell wall.
B) intact rhizobia in the plant cortex.
C) plant cells in the presence of symbiotic bacteria.
D) bacteroids in oxygen-rich nodules.
E) photosynthetic bacteroids in plants.

Accepted Answer

Nitrogen fixation is carried out by bacteroids, which are rhizobia that have undergone structural and functional changes in the presence of the legume host plant. Bacteroids lack a cell wall, which allows them to fix nitrogen in the anaerobic environment within the nodule. The other choices are incorrect, as intact rhizobia in the cortex, plant cells alone, and bacteroids in oxygen-rich nodules are not able to fix nitrogen efficiently in the symbiosis. Photosynthetic bacteroids are not typically found in legume-rhizobium symbiosis.