AIIMS 2004
- Exam
- AIIMS
- Year
- 2004
- Subject
- Botany
- Chapter
- Mineral Nutrition
AIIMS 2004 · Botany · Mineral Nutrition
Assertion : Nitrogen-fixing bacteria in legume root nodules survive...
Assertion : Nitrogen-fixing bacteria in legume root nodules survive in oxygen-depleted cells of nodules.
Reason : Legheamoglobin completely removes oxygen from the nodule cells.
Options
- AIf both assertion and reason are true and reason is the correct explanation of assertion
- BIf both assertion and reason are true but reason is not the correct explanation of assertion
- CIf assertion is true but reason is false
- DIf both assertion and reason are false.
Correct answer
A. If both assertion and reason are true and reason is the correct explanation of assertion
Step-by-step solution
Symbiotic nitrogen fixation occurs in legume plants. It takes place in the Rhizobium bacteroids which are located within root nodules cells. The important enzyme Nitrogenase (synthesised by Rhizobium ) that reduces , is oxygen sensitive. It can only function at low oxygen concentration. This low oxygen concentration in bacteriod is provided by leghaemoglobin. Leghaemoglobin (pink in colour) is a form of pigment found in the nitrogen fixing root nodules of legume. It binds oxygen and thus protects the nitrogen fixing enzyme, nitrogenase (that is oxygen sensitive). It regulates oxygen diffusion to bacteroids and nitrogenase.