The roots of the plant are most likely to test positive for nitrogenase. As Nitrogenase is produced by bacterial endosymbionts in roots.
Bacteria use nitrogen fixation as their method. The bacteria that fix nitrogen can live on their own or as symbionts in the roots of leguminous plants like soybeans, clover, and peas. Utilizing ATP and reducing equivalents derived from primary metabolism is necessary for nitrogen fixation.
Nitrogenase is made up of two proteins. An iron-containing protein called Nitrogenase Reductase (NR) receives electrons from a strong reductant called ferredoxin and delivers them to the other component called Nitrogenase, also known as Iron-Molybdenum protein.
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