Question 1

Where does Rhizobium live in a legume plant?

Accepted Answer

Rhizobium lives inside root nodules, where it occurs in differentiated bacteroid form. These bacteria fix atmospheric nitrogen and supply the plant with usable nitrogen compounds.

Question 2

How does mycorrhiza help a plant absorb nutrients?

Accepted Answer

Mycorrhizal fungal hyphae associate with the root and extend through the surrounding soil. Their fine network increases the volume of soil explored, improving water and mineral absorption, especially phosphate uptake.

Question 3

Where is Anabaena found in paddy fields?

Accepted Answer

Anabaena is shown free in the paddy-field water layer as a filamentous nitrogen-fixing cyanobacterium. It is not depicted as a root-nodule-forming bacterium attached to the root.

Question 4

How is Azospirillum different from Rhizobium?

Accepted Answer

Azospirillum is shown as free-living nitrogen-fixing rods in the rhizosphere of cereal roots. Rhizobium occurs inside characteristic root nodules of legumes, so the two partners have different locations and associations.

Question 5

What form of nitrogen do nitrogen-fixing microbes provide first?

Accepted Answer

Nitrogen-fixing microbes convert atmospheric nitrogen gas, N2, into ammonia. Plants use this fixed nitrogen for making nitrogen-containing biological compounds.

Biofertilisers at Work: Rhizobium, Mycorrhiza, Anabaena & Azospirillum

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Practice