Question

Explain the role of the pink color pigment in the root nodules of legume plants. What is it called?

Answer 1

Root nodules are found on the roots of plants, mostly legumes that form a symbiosis with nitrogen fixing bacteria. It functions as the result of interaction between the host plant and the soil bacteria. The legume plants play an important role in the genesis of the nodule formation.

Complete answer: Nodules are present in the roots of the leguminous plants. The bacterium is named as Rhizobium spp. Is responsible for the formation of nodules. The nodules appear pink in colour due to the presence of Leghemoglobin which is an iron-containing pigment pink in colour. The pigment is used to scavenge oxygen for the functioning of the enzyme nitrogenase in nitrogen fixation.
These are the root nodules of leguminous plants caused by nitrogen fixing bacteria. They help in converting nitrogen into nitrates which the plants can utilize. They use the nitrogen to synthesize proteins and other materials. The “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. It acts as the biological value in regulating the supply of oxygen into the tissue. Oxygen supply at an optimum rate to cover the maximum activity of the enzyme “nitrogenase” which is the key factor in the nitrogen fixation.

Note: As the nodules grow in size, they gradually turn pink or reddish in colour, it indicates nitrogen fixation has started. The pink colour of the nodule is caused by the leghemoglobin similarly like hemoglobin in blood that controls oxygen flow to the bacteria. Nitrogen fixation is the process by which nitrogen is converted into the ammonia or related nitrogenous compounds.