Question

Rhizobium bacteria and root nodules of Pea have an association called
(A) Predation
(B) Parasitism
(C) Symbiosis
(D) Commensalism
(E) Scavenging

Answer 1

Rhizobium is a genus of Gram-negative soil bacteria that fix nitrogen.Swelling on the root of a leguminous plant, such as the pea or clover, that contains bacteria of the genus Rhizobium, capable of nitrogen fixation.Root nodules are found on the roots of plants.

Complete answer:
The pea plant is considered under the category of leguminous plants. They consist of legumes and these legumes are capable enough for forming symbiotic association with the nitrogen-fixing bacteria in the soil called rhizobia. This bacterium takes the atmospheric nitrogen and transfers it to the plants, which assists the growth of the plant even in the soil having low nitrogen content. The Rhizobium bacteria inhabit soil and through the process of symbiosis, it associates with the legumes of the pea plant that are present in its root nodules. Lack of nitrogen causes the release of the flavonoids from the legumes that are in symbiotic relationships. These flavonoids send the signals to the bacterium related to their requirement, and the bacteria responses with its association with the root nodules of the pea plant. Rhizobia live in the soil. When there is limited soil nitrogen, legumes in symbiotic relationships release flavonoids which sends a signal to rhizobia that the plant needs symbiotic bacteria. Rhizobium produces ammonia from the atmospheric nitrogen and assists the plant's growth.The Rhizobium bacteria and root nodules of pea have a symbiotic relation with each other. The root nodules are present in the legumes of the pea plant. Therefore, the correct answer is symbiosis.

Hence, the correct answer is option ‘C’.

Note: The bacteria Rhizobium is aerobic in nature, which has much to do with the fact that the process of fixation of nitrogen is an energy rigorous process which necessitates a great quantity of energy that cannot be possibly produced via anaerobic pathways. These bacteria obtain their essential nutrients from the plants for which they fix the nitrogen.