Q. Which of the following are nitrogen-fixing plants?

Explanation : 

Nitrogen Fixation in Plants

Nitrogen fixation is a process by which certain plants, often in a symbiotic relationship with soil bacteria, convert atmospheric nitrogen (N₂) into a form that can be used by living organisms (usually ammonia or related compounds). This process is critical for replenishing soil nitrogen levels, which is essential for plant growth.

Known Nitrogen-Fixing Plants

Alfalfa (Medicago sativa) is a well-known nitrogen-fixing plant. It forms a symbiotic relationship with rhizobia bacteria within its root nodules, which fix atmospheric nitrogen into a form that the plant can use.

Amaranth (Amaranthus spp.) is not a nitrogen-fixing plant. It does not form symbiotic relationships with nitrogen-fixing bacteria and thus does not fix atmospheric nitrogen.

Chickpea (Cicer arietinum) are legumes that also fix nitrogen. They have root nodules that house rhizobia bacteria, which perform the nitrogen fixation process.

Clover (Trifolium spp.) is another legume that fixes nitrogen. Like alfalfa and chickpeas, clover plants have root nodules with rhizobia bacteria that convert atmospheric nitrogen into a usable form for the plant.

Purslane (Kulfa) (Portulaca oleracea) is not a nitrogen-fixing plant. It is known for its ability to grow in poor soil conditions, but it does not have the ability to fix atmospheric nitrogen.

Spinach (Spinacia oleracea) is also not a nitrogen-fixing plant. It requires nitrogen in the soil to grow but does not contribute to soil nitrogen levels through fixation.

Based on this information, the correct answer to the question is “1, 3 and 4 only.” Alfalfa, chickpea, and clover are the only plants on the list that are known to fix nitrogen.