Question

Nitrogen fixation in root nodules of Alnus is brought about by?

• A. Frankia
• B. Clostridium
• C. Bradyrhizobium
• D. Azorhizobium

Answer 1

The correct option is A

Frankia

The correct option is A:

Explanation for the correct option:

1. Frankia is a gram-positive bacterium that lives on plant roots.
2. The fact that Frankia is gram-positive indicates that the bacteria have thick cell walls formed of peptidoglycan.
3. This aids resistance to heavy metals that may be present in deteriorated soil.

Explanation for the incorrect options:

Option B:

Clostridium is a Gram-positive bacterium genus.

This genus contains several important human infection causing organisms, including botulism and tetanus causal agents.
Option C:

Bradyrhizobium is one of several nitrogen-fixing bacteria species that can produce symbiotic nodules in legumes.
Option D:

Azorhizobium is a Gram-negative soil bacterium genus.

They live in symbiosis with plants in the genus Sesbania and have nitrogen fixing functions.

Final answer: Nitrogen fixation in root nodules of Alnus is brought about by Frankia.