Question

Assertion: Nitrogen-fixing bacteria in legume root nodules survive in oxygen-depleted cells of nodules.

Reason: Legheamoglobin completely removes oxygen from the nodule cells.

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true but R is not correct explanation of A

(c) A is true but R is false

(d) A and R are false

Answer 1

The correct option is: (a)

Explanation:

Symbiotic nitrogen fixation occurs in legume plants. It takes place in the Rhizobium bacteroids which are located within root nodules cells. The important enzyme Nitrogenase (synthesised by Rhizobium) that reduces N₂, is oxygen sensitive. lt can only function at low oxygen concentration. This low oxygen concentration in bacteroid is provided by leghaemoglobin. Leghaemoglobin (pink in colour) is a form of pigment found in the nitrogen fixing root nodules of legume. It binds oxygen and thus protects the nitrogen fixing enzyme, nitrogenase (that is oxygen sensitive). It regulates oxygen diffusion to bacteroids and nitrogenase.