Question

Root nodules for nitrogen fixation of a non-leguminous tree possess
A. Frankia
B. Rhizobium
C. Azotobacter
D. Thiobacillus

Answer 1

It belongs to a nitrogen-fixing genus. This bacterium lives in symbiosis with actinorhizal plants and is identical to Rhizobium bacteria found in leguminous roots.

Complete answer:
On plant roots, mainly legumes that form symbiosis with nitrogen-fixing bacteria, root nodules are found. Capable plants form a symbiotic connection with a host-specific strain of bacteria known as rhizobia under nitrogen-limiting conditions. In legumes and in other forms found in the Rosid clade, this process has evolved many times. Nitrogen gas from the environment in legume root nodules is transformed into ammonia and is eventually assimilated to amino acids, nucleotides and other cellular components such as vitamins, flavones and hormonal substances. Their ability to fix gas nitrogen makes legumes suitable for cultivation, as their nitrogen fertiliser needs are decreased.
There are only two plant classes that may join root nodule symbiosis with nitrogen fixation: legumes and actinorhizal plants. Legumes are commonly regarded as rhizobia with bacteria. Actinorhizal plants can develop endosymbiosis by means of the actinomycete Frankia, a nitrogen-fixing plant. The symbiotic process is produced to generate root nodules in the host plant in exchange for reduced carbon in Frankie's supply of fixed nitrogen.

Thus, the correct answer is option A. i.e., Frankia.

Note: Frankia forms root nodules of plants like actinorhizal plants that have no leguminous material. A symbiotic relation to leguminous plants is established with Rhizobium. Azotobacter is bacteria that freely live and fix nitrogen. Nitrogen fixation is not related to Thiobacillus.