Question

Match List I with List II

• A. A(I), B(II), C(IV), D(III)
• B. A(IV), B(III), C(II), D(I)
• C. A(IV), B(II), C(III), D(I)
• D. A(IV), B(I), C(III), D(II)

Hint:

Mycorrhizae = Phosphorus.
Nitrosomonas = Ammonia -> Nitrite (Nitrification).
Symbiosome = N2 fixation site in plants.
Nitrogenase enzyme is oxygen-sensitive, requiring microaerophilic conditions.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question requires matching different microorganisms or microbial structures with their specific functional roles in plant growth and soil cycles.

Step 2: Detailed Explanation:

• A. Mycorrhizae: These are symbiotic associations between fungi and plant roots. Their primary role is to increase the surface area for nutrient absorption, specifically enhancing the uptake of phosphorus, which is often immobile in soil. Hence, A matches with IV.

• B. Symbiosome: This is the structural unit in the root nodules of legumes consisting of the bacteroids (nitrogen-fixing bacteria) surrounded by a host-derived peribacteroid membrane. It is the site of symbiotic nitrogen fixation. Hence, B matches with III.

• C. Azospirillum: This is an associative nitrogen-fixing bacterium. It is characterized by its ability to fix nitrogen efficiently under microaerophilic (low oxygen) conditions, as oxygen inhibits the nitrogenase enzyme. Hence, C matches with II.

• D. Nitrosomonas: This is a genus of chemoautotrophic bacteria that performs the first step of nitrification. They oxidize ammonia into nitrite ($NO_2^-$). Hence, D matches with I.

Step 3: Final Answer:
The matching sequence is A-IV, B-III, C-II, D-I. This is represented by option (B).