Consider the following statements regarding the nitrogen cycle:
1. Nitrosomonas bacteria convert ammonia into nitrites, while Nitrobacter bacteria convert nitrites into nitrates.
2. Denitrification is a process that increases soil fertility by converting atmospheric nitrogen into ammonia.
3. Leguminous plants contribute to nitrogen fixation through a symbiotic relationship with Rhizobium bacteria.

Which of the statements given above are correct?
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2, and 3

Question

Consider the following statements regarding the nitrogen cycle:
1. Nitrosomonas bacteria convert ammonia into nitrites, while Nitrobacter bacteria convert nitrites into nitrates.
2. Denitrification is a process that increases soil fertility by converting atmospheric nitrogen into ammonia.
3. Leguminous plants contribute to nitrogen fixation through a symbiotic relationship with Rhizobium bacteria.

Which of the statements given above are correct?
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2, and 3

ONLiNE UPSC · Accepted Answer

Statement 1 is correct: Nitrosomonas bacteria convert ammonia (NH3) into nitrites (NO-2), and Nitrobacter bacteria convert nitrites (NO-2) into nitrates (NO-3). This process, called nitrification, makes nitrogen available to plants.
Statement 2 is not correct: Denitrification is carried out by bacteria like Pseudomonas and Clostridium, which convert nitrates (NO-3) back into nitrogen gas (N2), releasing it into the atmosphere. This reduces soil fertility rather than increasing it.

Statement 3 is correct: Leguminous plants (such as peas and beans) form a symbiotic relationship with Rhizobium bacteria, which fix atmospheric nitrogen (N2) into ammonia (NH3), making it available for plant use.

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M Question 1	⏱ 0
Consider the following statements regarding the nitrogen cycle: 1. Nitrosomonas bacteria convert ammonia into nitrites, while Nitrobacter bacteria convert nitrites into nitrates. 2. Denitrification is a process that increases soil fertility by converting atmospheric nitrogen into ammonia. 3. Leguminous plants contribute to nitrogen fixation through a symbiotic relationship with Rhizobium bacteria. Which of the statements given above are correct? (a) 1 and 2 only (b) 2 and 3 only (c) 1 and 3 only (d) 1, 2, and 3