Leghaemoglobin - Factors Influencing Functions of Nitrogenase

Leghaemoglobin is a joint product of Rhizobium and the host. It is produced during the maturation of nodule. It is commonly observed that nodules containing leghaemoglobin look pink in colour and those deficient in it look colourless. Pink coloured nodules are always effective in N₂-fixation while the colourless ones are unable to fix N₂. The inability to synthesise leghaemoglobin is associated with lack of N₂-fixing ability. Leghaemoglobin serves a dual function.

It functions as a reservoir of oxygen and thus provides enough O₂, to the bacteroid for the production of ATP through aerobic respiration. Secondly, it has the ability to bind diffusing oxygen within the nodule, so it keeps oxygen away from nitrogenase.