Question

For what reason is the leguminous soil beneficial.
A. Deer won’t eat them
B. They are photosynthetic
C. They have nitrogen fixing bacteria in their roots
D. Animals convert them into energy
E. None of the above

Answer 1

Hint: The conversion of nitrogen into salts of nitrogen like ammonia is called nitrogen fixation. When nitrogen fixation is done by living organisms, it is called biological nitrogen fixation.

Complete step by step answer:
In biological nitrogen fixation, nitrogen fixation is done by living organisms. It is done mainly by nitrogen-fixing bacteria present in the soil. In leguminous plants, a special structure is formed in the roots in which nitrogen fixation takes place. It is called a root nodule. Nodule formation occurs when certain bacteria enter the roots of these leguminous plants. Rhizobium is the bacteria that causes this in legumes. When it comes in contact with the root, the root hair curls, and the infection thread enters the root. Bacteria produce cytokines that help in promoting cell division which leads to nodule formation. The main enzyme seen inside the root nodule is enzyme nitrogenase and leghemoglobin. Nitrogenase is the enzyme that catalyzes the process of nitrogen fixation. This enzyme is highly sensitive to oxygen. Leg haemoglobin acts as the oxygen scavenger and protects the enzyme nitrogenase from oxygen. Leguminous soil in which these leguminous plants grow is rich in nitrogen-fixing bacteria. So, this soil is rich in nitrogen and increases the fertility of the soil.
Hence the correct option is C.

Note: It is a symbiotic relationship that is seen inside the root nodule between Rhizobium and the plant. Legume plants include pea, beans, and sweet pea. This type of relationship is beneficial to both of the organisms.