Which of the Following is a True Statement About Nitrogen

Question

Which of the following is a true statement about nitrogen fixation in root nodules?
A) The plant contributes the nitrogenase enzyme.
B) The process is relatively inexpensive in terms of ATP costs.
C) Leghemoglobin helps maintain a low O₂ concentration within the nodule.
D) The process tends to deplete nitrogen compounds in the soil.
E) The bacteria of the nodule are autotrophic.

Accepted Answer

Leghemoglobin binds to oxygen, allowing for a low concentration of O₂ within the nodule, which is important for nitrogen fixation.

Answer: D
 Nitrogen fixation in root nodules can deplete nitrogen compounds in the soil because the fixation process uses up available nitrogen.

Answer: A and B are incorrect 
 The plant does not contribute the nitrogenase enzyme to the nodule, and nitrogen fixation in root nodules is actually energetically expensive (requiring ATP). Answer E is also incorrect, as the bacteria in the nodule are heterotrophic, deriving energy from the plant.