Answer: Toxic to the plant.
- A Highly beneficial
- B Simply ignored
- C Toxic to the plant
- D Changed to oxygen
Correct answer: C. Toxic to the plant
Explanation: Free ammonia is toxic, so it is rapidly converted into amino acids (via glutamine/glutamate) inside the plant.
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.