Question 56 from UPSC CSE 2022 - Environme nt

Question

Which of the following are nitrogen-fixing plants?
1. Alfalfa
2. Amaranth
3. Chickpea
4. Clover
5. Purslane (Kulfa)
6. Spinach
Select the correct answer using the code given below:

IASCODEX · Accepted Answer

Correct Option: A. 1, 3, and 4 only

Strategy: - Identify classic nitrogen-fixing plants, particularly legumes (Fabaceae), which host symbiotic bacteria in root nodules.
- Alfalfa, chickpea, and clover are legumes known for nitrogen fixation.
- Amaranth, purslane, and spinach are not legumes and do not fix nitrogen; they lack symbiotic root nodules.
- Therefore, the correct option contains only alfalfa, chickpea, and clover.

Key Info: Nitrogen fixation in plants is mainly associated with members of the Fabaceae (legume) family due to their symbiotic relationship with Rhizobium bacteria.

- **Alfalfa** (*Medicago sativa*): A perennial legume known for forming nodules with nitrogen-fixing bacteria, commonly cultivated as forage.
- **Chickpea** (*Cicer arietinum*): An annual legume crop capable of fixing atmospheric nitrogen through symbiotic relationships in its roots.
- **Clover** (*genus Trifolium*): Includes numerous species of herbaceous legumes, valued for their nitrogen-fixing abilities via root nodules and extensive use in pastures and cover crops.
- **Amaranth** (*genus Amaranthus*): Not a legume; lacks nitrogen-fixing ability. Cultivated mostly for its grains and edible leaves.
- **Purslane** (*Portulaca oleracea*): A succulent, non-leguminous leafy vegetable with no nitrogen-fixing capacity.
- **Spinach** (*Spinacia oleracea*): A leafy green vegetable of the Amaranthaceae family, does not fix nitrogen, and is unrelated to the legume family.

Nitrogen-fixing plants are agriculturally important as they improve soil fertility by increasing bioavailable nitrogen, often reducing the need for synthetic fertilizers. Their use in crop rotations or intercropping enhances sustainable farming systems.

IASCODEX · Answer

Option B: 1, 3, 5, and 6 only

IASCODEX · Answer

Option C: 2, 4, 5, and 6 only

IASCODEX · Answer

Option D: 1, 2, 4, 5, and 6

Which of the following are nitrogen-fixing plants? Alfalfa Amaranth Chickpea Clover Purslane (Kulfa) Spinach Select the correct answer using the code given below:

Which of the following are nitrogen-fixing plants?

Alfalfa

Amaranth

Chickpea

Clover

Purslane (Kulfa)

Spinach
Select the correct answer using the code given below: