Question

Which is the red pigment found in the root nodules of legume plants?
A. Phycoerythrin
B. Bacteriochlorophyll
C. Leghaemoglobin
D. Bacterioviridin

Answer 1

Hint: The root nodules of leguminous plants are concerned with the fixation of nitrogen with the help of nitrogen-fixing bacteria Rhizobium and nitrogen-fixing enzymes.

Complete answer:
Leguminous plants have a symbiotic association with nitrogen-fixing bacteria like Rhizobium. These bacteria are responsible for fixing nitrogen from the atmosphere. Rhizobium enters the root nodules and performs the function of fixing bacteria with the help of the nitrogen-fixing enzyme Nitrogenase. This Nitrogenase is very susceptible to oxidation and so, there is the presence of a pigment that protects it from getting destroyed.
Phycoerythrin is a red pigment complex that is found in Red algae also known as Rhodophyceae and Cryptophytes. This pigment is responsible for photosynthesis in red algae.
Hence, option (a) is not correct.
Bacteriochlorophyll is a photosynthetic pigment found in autotrophic bacteria, especially purple sulfur bacteria and purple non-sulfur bacteria. It is a form of chlorophyll but not green in color but purple or brown.
Hence, option (b) is also incorrect.
Bacterioviridin is a pigment found in photosynthetic green sulfur bacteria, unlike bacteriochlorophyll which is present in purple sulfur and purple non-sulfur bacterias. It consists of chlorobium chlorophyll as the major component.
So, option (d) is also not correct.
The root nodules contain a respiratory pigment called Leghaemoglobin, which is responsible for carrying oxygen and protecting enzyme nitrogenase from oxidation. It is named so, as it is found in Leguminous plants.
So, the correct answer is “Option C”.

Note:
The root nodules of leguminous plants consist of a red pigment which is referred to as the respiratory pigment. Leghaemoglobin, named so because it is found in the leguminous plants, is responsible for carrying oxygen and preventing nitrogenous enzyme nitrogenase from oxidation.