📘 Q.9 IAS Prelims 2022— Environment & Ecology (Nitrogen-Fixing Plants)🧷 Authentic Classroom Explanation by IAS Monk
📌 The Question:
Which of the following are nitrogen-fixing plants?
- Alfalfa
- Amaranth
- Chickpea
- Clover
- Purslane (Kulfa)
- Spinach
Select the correct answer using the code given below:
(a) 1, 3 and 4 only
(b) 1, 3, 5 and 6 only
(c) 2, 4, 5 and 6 only
(d) 1, 2, 4, 5 and 6
✅ Correct Answer: (a) 1, 3 and 4 only
🧠 Classroom Explanation:
• Alfalfa (Correct)
Alfalfa (Lucerne) belongs to the Fabaceae (legume) family.
It forms a symbiotic relationship with Rhizobium bacteria in root nodules, enabling biological nitrogen fixation.
• Amaranth (Incorrect)
Amaranth (Amaranthus) is not a legume and does not form nitrogen-fixing root nodules.
• Chickpea (Correct)
Chickpea is a leguminous crop (Fabaceae) and fixes atmospheric nitrogen through Rhizobium symbiosis.
• Clover (Correct)
Clovers are classic nitrogen-fixing legumes, widely used in crop rotation to enrich soil fertility.
• Purslane (Incorrect)
Purslane (Portulaca oleracea) is a succulent leafy vegetable, not a legume and does not fix nitrogen.
• Spinach (Incorrect)
Spinach belongs to Amaranthaceae, not Fabaceae, and lacks nitrogen-fixing capability.
Hence, only Alfalfa, Chickpea and Clover are nitrogen-fixing plants.
🔍 Curiosity Raiser:
Why does UPSC repeatedly test legumes vs non-legumes, even when both are leafy or protein-rich crops?
📚 Enrich Notes (Prelims Gold):
• Nitrogen fixation = Legume + Rhizobium
• Fabaceae family = UPSC shortcut
• Leafy ≠ Nitrogen-fixing
• Common nitrogen-fixers: pulses, clover, alfalfa, peas, beans
🪶 IAS Monk Whisper:
When soil becomes fertile, crops rise silently. Legumes are nature’s quiet engineers.