- A Viruses that trigger nodule formation
- B Rhizobium bacteria (nitrogen fixers)
- C Mycorrhizal fungi that enhance phosphorus uptake
- D Actinomycetes that decompose dead root tissue
Correct answer: B. Rhizobium bacteria (nitrogen fixers)
Explanation: Rhizobium bacteria live symbiotically in root nodules of legumes. They fix atmospheric N2 into ammonia used by the plant.
Concept context
Essential mineral elements, their roles and deficiency symptoms. Nitrogen fixation and soil nutrition.