Assertion : Nitogen - fixing bacteria in legume root nodules survive in oxygen - depleted cells of nodules.
Reason : Leghaemoglobin completely removes oxygen from the nodule cells.

Options

A. If both assertion and reason are true and reason is the correct explaination of assertion
B. If both assertion and reason are true but reason is not correct explaination of assertion
C. If assertion is true but reason is false
D. If both assertion and reason are false.

Answer

D

Explanation

Symbiotic nitrogen fixtion occurs in lengume plants.It take place in the rhizobium bactroids which are located within root nodules cells.Rhizobium is an aerobic bacteria and hence it survive in presence of oxygen.But the important enzyme Nitrogenase (synthesise by rhizobium)that reduces`N_(2)`,is oxygen sensitive.It can only fuction at low oxygen concentration.This low oxygen concentration in bacteriod is provided by leghaemoglobin.Leghaemoglobin(Pink in colour)Is a form of haemoglobin found in the nitrogen fixing root nodules of legume.They bound oxygen and thus protect the nitrogen fixing enzyme,nitrogenase(That is oxygen sensitive).It regulates oxygen diffusion to bacteriods and nitrogenase.