Answer: About 17 elements.
- A About 17 elements
- B About 4 elements
- C About 30 elements
- D About 50 elements
Correct answer: A. About 17 elements
Explanation: Around 17 elements are considered essential for plant growth and development.
Atmospheric N₂ is fixed into ammonia by nitrogen-fixing bacteria (protected from oxygen by leghaemoglobin in root nodules), converted to nitrate via nitrification for plant uptake, and eventually returned to the atmosphere as N₂ via denitrification, completing the cycle.
Concept context
Essential mineral elements, their roles and deficiency symptoms. Nitrogen fixation and soil nutrition.