Question

Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R

Assertion (A) : Root nodules of legumes are internally pinkish or red coloured.

Reason (R) : The legume root nodules contain leghaemoglobin.

In the light of the above statements, choose the correct answer from the options given below

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

Answer 1

The Correct Option is A

Certain symbiotic nitrogen fixing bacteria invade roots of leguminous plants and initiate nodule formation. Nodule formation is stimulated by auxin produced by cortical cells and cytokinin liberated by invading bacteria. The infected cells enlarge. Bacteria stop dividing and form irregular polyhedral structures called bacteroids. In an infected cells, bacteroids occur in groups surrounded by host membrane. The host cell develops a pinkish pigment called leghaemoglobin (Lb). Leghaemoglobin has ten times more affinity for oxygen as compared to blood pigment haemoglobin. Leghaemoglobin acts as oxygen scavenger. It protects nitrogen fixing enzyme nitrogenase from oxygen.