Question

Bacterium associated with legume roots is
A. Rhizobium
B. Nostoc
C. Spirogyra
D. Clostridium

Answer 1

Hint: The organism which is associated with leguminous plants is a bacterium that is gram-negative bacteria.

Step by step answer:In option A, Rhizobium is mentioned. Rhizobium is a genus of bacteria. These bacteria live in symbiosis with legumes. They are present in the soil. They attach themselves to the roots of the leguminous plant and form nodules.
In option B, Nostoc is mentioned. It belongs to a genus of cyanobacteria/blue-green algae. It contains two pigments that are blue phycocyanin and red phycoerythrin. Also, they contain chlorophyll. They have the ability to fix the nitrogen in specialized cells called heterocysts. It has been researched that Nostoc is used in secondary metabolite reproduction which is considered harmful for human beings.
In option C, Spirogyra is mentioned. It is also known as water silk. It is an alga. It has a spherical arrangement of chloroplasts which makes it renowned.
In option D, Clostridium is mentioned. It is a genus of bacteria. They are gram-positive. The members of this genus are human pathogens. They are the causative agents for diseases like tetanus and botulism.

So, the correct option is option A

Note: The symbiotic relationship between Rhizobium and the plants. A symbiotic relationship between two species or organisms is a type of interdependent relation. Both of the organisms involved rely on each other for something valuable. The Rhizobium forms nodules. These nodules fix atmospheric nitrogen for plants in those nodules and convert them into ammonia which can be used by the plant for its growth and development. They, in return, get nutrition for their survival.