Correct Option
Nitrogen-fixing plants typically form a symbiotic relationship with specific bacteria, primarily Rhizobium, which reside in root nodules. These bacteria convert atmospheric nitrogen (N₂) into ammonia (NH₃), a form usable by plants. The following plants are known for their nitrogen-fixing capabilities:
- Alfalfa (Medicago sativa): This is a leguminous plant widely cultivated as forage. It forms root nodules with nitrogen-fixing bacteria.
- Chickpea (Cicer arietinum): A pulse crop belonging to the legume family (Fabaceae). It is known for its ability to fix atmospheric nitrogen through symbiosis with Rhizobium.
- Clover (Trifolium species): Various species of clover are leguminous plants commonly used as cover crops and for pasture. They host nitrogen-fixing bacteria in their root nodules.
Incorrect Options
The following plants do not possess the ability to fix atmospheric nitrogen:
- Amaranth (Amaranthus species): This is a pseudocereal and a leafy vegetable. It belongs to the Amaranthaceae family and does not form symbiotic relationships with nitrogen-fixing bacteria.
- Purslane (Portulaca oleracea): A succulent herbaceous plant, it belongs to the Portulacaceae family. It is not a legume and does not fix nitrogen.
- Spinach (Spinacia oleracea): A leafy green vegetable belonging to the Amaranthaceae family. Spinach is a nitrogen-consuming plant and does not engage in nitrogen fixation.