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:
- 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
Explanation
The correct answer is A, 1, 3 and 4 only. Alfalfa, chickpea and clover are legumes, and legumes fix nitrogen.
Plants of the legume family (Fabaceae) carry root nodules that house Rhizobium bacteria. These bacteria use the enzyme nitrogenase to turn nitrogen gas from the air into ammonia, which the plant uses to make proteins. In return the plant gives the bacteria sugars and shelter. This is why farmers grow pulses and fodder legumes in rotation with cereals: they enrich the soil with nitrogen and cut the need for urea. Alfalfa (lucerne) and clover are fodder legumes, and chickpea (gram) is a major pulse of India.
B is wrong because purslane and spinach are not legumes and do not fix nitrogen. C is wrong because amaranth, purslane and spinach are leafy plants without root nodules; only clover in that list fixes nitrogen. D is wrong because it includes amaranth, purslane and spinach and leaves out chickpea.
Exam tip: Legumes + Rhizobium root nodules = nitrogen fixation; gram, alfalfa and clover are legumes.
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