Question

Rhizobium is found in
A. Maize Root
B. Gram Root
C. Branch of a plant
D. Sugarcane root

Answer 1

Hint: After being formed within the root nodules of legumes, diazotrophic bacteria that fix nitrogen. Rhizobia needs a plant host to express genes for nitrogen fixation; they do not independently fix nitrogen.

Complete Answer:
Rhizobia is a group of soil bacteria that, in order to form root nodules, infect the roots of legumes. Rhizobia are present in the soil and develop nodules in the legume after infection, where they fix nitrogen gas ( $N_2$ ) from the atmosphere, converting it into a nitrogen type that is more readily available.
The nitrogen from the nodules is exported from here and used for legume growth. When the legume dies, the nodule breaks down and releases the rhizobia back into the soil, where they can live individually or reinfect a new legume host.

- While much of the nitrogen is removed when protein-rich grain or hay is harvested, for future crops, large quantities will remain in the soil. This is particularly important if nitrogen fertiliser is not used, as in organic rotation systems or in some less-industrialized countries.
- In many soils around the world, nitrogen is the most commonly deficient nutrient and the most commonly supplied plant nutrient. There are serious environmental issues with the supply of nitrogen through fertilisers.
- To make functional nodules on the roots capable of fixing the $N_2$, unique strains of rhizobia are needed. It is advantageous for the legume to have this particular rhizobium present, as the $N_2$ fixation will increase crop yield. Rhizobia inoculation helps to increase yield.

So the answer is ‘B’.

Note: For several years, legume inoculation has been an agricultural activity and has steadily developed over time. Annually, 12-20 million hectares of soybeans are inoculated. Microbial fermenters are the technology for generating these inoculants. Some of the following factors include an ideal inoculant; optimum effectiveness, ease of use, compatibility, high rhizobial concentration, long shelf-life, usefulness and survival under varying field conditions.