What is the role of bacteria in the nodules of alfalfa roots?

Bacteria in the nodules of alfalfa roots play a crucial role in a symbiotic relationship that is highly beneficial to the plant. These bacteria, specifically known as rhizobia, have the ability to fix atmospheric nitrogen, converting it into a form that is usable by the plant. This process is essential because nitrogen is a vital nutrient required for plant growth and development.

Alfalfa, being a legume, can thrive in nitrogen-poor soils due to this partnership. The nitrogen fixed by the bacteria enhances the nutritional status of the plant, leading to better growth and yield. In return, the bacteria receive carbohydrates and other organic compounds from the plant, which serve as their energy source. This symbiotic relationship not only supports the alfalfa plant but also improves soil fertility in the long term, benefiting subsequent crops grown in the same soil.

In contrast, options that suggest the bacteria are harmful, have no impact, or only affect soil quality do not accurately reflect the established scientific understanding of the relationship between these bacteria and alfalfa. The symbiosis is key to improving both plant health and soil nutrient levels, making the choice that identifies their role as beneficial the correct one.