Bacteria in root nodules change nitrogen gas (\(N_2\)) into what form?

• A. Nitrite (\(NO_2^-\))
• B. Nitrate (\(NO_3^-\))
• C. Urea (\(CO(NH_2)_2\))
• D. Ammonia (\(NH_3\))

Answer: (D)

Verified step by step guidance

1. Understand the role of bacteria in root nodules: These bacteria, often from the genus Rhizobium, are involved in nitrogen fixation, a process that converts atmospheric nitrogen gas (\(N_2\)) into a usable form for plants.
2. Recognize the chemical transformation: Nitrogen gas (\(N_2\)) is highly stable and must be converted into a biologically accessible form. The bacteria use the enzyme nitrogenase to catalyze this conversion.
3. Identify the product of nitrogen fixation: The enzyme nitrogenase reduces \(N_2\) to ammonia (\(NH_3\)), which is the primary form of nitrogen produced during this process.
4. Clarify why ammonia (\(NH_3\)) is the correct answer: Ammonia can be further processed by plants into other nitrogen-containing compounds, such as amino acids, which are essential for growth and development.
5. Note the distinction from other nitrogen compounds: Nitrite (\(NO_2^-\)), nitrate (\(NO_3^-\)), and urea (\(CO(NH_2)_2\)) are not direct products of nitrogen fixation by root nodule bacteria. These compounds may form later through other processes like nitrification or metabolic pathways.