Question

Given below are two statements:
Statement (I): Molybdenum is a component of nitrate reductase, nitrogenase, xanthine oxidase/dehydrogenase and sulphite oxidase.
Statement (II): The critical concentration of molybdenum-deficiency in plants is usually more than 0.1 ppm and its deficiencies resemble the N-deficiencies.
In light of the above statements, choose the most appropriate answer from the options given below.

• A. Both Statement (I) and Statement (II) are correct.
• B. Both Statement (I) and Statement (II) are incorrect.
• C. Statement (I) is correct but Statement (II) is incorrect.
• D. Statement (I) is incorrect but Statement (II) is correct.

Hint:

Recall the standard list of Mo enzymes and the typical critical tissue level for Mo deficiency.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
This question checks two separate facts about molybdenum (Mo), the micronutrient plants need in the smallest amount of all, which enzymes it is built into, and how low its tissue level has to fall before deficiency shows up.

Step 2: Key Formula or Approach:
Judge each statement on its own first. Statement I is a list of Mo-containing enzymes, Statement II combines a numeric threshold with a symptom description, so both parts of Statement II need to be right for the whole statement to count as correct.

Step 3: Detailed Explanation:
Checking Statement I: Molybdenum acts as a metal cofactor in several plant enzymes. Nitrate reductase, which converts nitrate to nitrite during nitrogen assimilation, needs Mo. Nitrogenase, the enzyme symbiotic bacteria use to fix atmospheric \(N_2\), also needs Mo. Xanthine oxidase/dehydrogenase (purine breakdown) and sulphite oxidase (sulphur metabolism) need Mo as a cofactor too. This matches the standard list of Mo-dependent enzymes taught in plant nutrition, so Statement I is correct.
Checking Statement II: Molybdenum is needed by plants in tiny amounts, and its critical tissue concentration, the level below which deficiency symptoms appear, is usually quoted at around or below 0.1 ppm dry matter, not "more than 0.1 ppm". Statement II reverses this direction, so the numeric part is wrong, even though the second half, that Mo deficiency looks like N-deficiency because Mo is needed for nitrate reductase and nitrogenase, both nitrogen-related enzymes, is a genuine and well known fact. Since the statement combines a wrong number with a right description, the statement as a whole is incorrect.

Step 4: Final Answer:
Statement I is correct, Statement II is incorrect, so option 3 is the answer.