The function of leghaemoglobin is
(a) to provide oxygen to leg muscles of nitrogen-fixing
(b) to protect oxygen-sensitive enzymes of nitrogen fixing bacteria in the root nodules of legumes
(c) to walk to the sites where oxygen is required
(d) to function when haemoglobin is not available.
(b): Leghaemoglobin is a form of haemoglobin found in the nitrogen-fixing root-nodules of legumes. A cross section of a mature nodule reveals a pink or red coloured central bacteroid zone surrounded by thin walled cells. The red colour is caused by the presence of "leghaemoglobin, the prefix "leg" indicates its unique presence in root nodules of leguminous plants. The amount of red pigment in nodules is directly proportional to the amount of nitrogen fixed by nodules. The red pigment in the nodules acts as a biological value in regulating the supply of oxygen into the bacteroid tissue, binds oxygen, and thus protects the nitrogen-fixing enzyme, nitrogenase, that is oxygen sensitive. The supply of oxygen at an optimum rate to help the maximum activity of the enzyme "nitrogenase" which is key factor in the mechanism of nitrogen fixation.