Answer: Growth becomes reduced.
- A Growth becomes fastest
- B Growth becomes reduced
- C The plant dies instantly
- D There is no effect
Correct answer: B. Growth becomes reduced
Explanation: The critical concentration is the minimum needed for normal growth; below it, deficiency reduces growth.
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.