Q1. Higher plants take up Nitrogen as
(a) Nitrites only
(b) Nitrates only
(c) Nitrates and ammonia
(d) Urea
(UPSC Prelims, 1979)
Answer: (b) Nitrates only
Explanation: Higher plants absorb nitrogen primarily in the form of nitrates, which are soluble and easily transported through the soil. Nitrates are converted into amino acids and proteins, essential for plant growth and development.
Q2. Which of the following crops helps in nitrogen fixation ?
(a) Rice
(b) Wheat
(c) Maize
(d) Beans
(UPSC Prelims, 1979)
Answer: (d) Beans
Explanation: Beans, being leguminous plants, have symbiotic bacteria (Rhizobium) in their root nodules that fix atmospheric nitrogen into the soil. This process enriches soil fertility, reducing the need for synthetic nitrogen fertilisers.
