Which of the following microbe serves as an important biofertiliser in paddy field?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Cyanobacteria
Option (1) Cyanobacteria — Correct. They grow in the standing water of the paddy field and fix nitrogen.
Option (2) Rhizobium — Incorrect. Rhizobium fixes nitrogen only in the root nodules of leguminous plants. Rice is not a legume.
Option (3) Mycorrhiza — Incorrect. Mycorrhiza is an association of a fungus such as Glomus with roots; it mainly helps the plant absorb phosphorus. NCERT does not name it for paddy fields.
Option (4) Bacillus thuringiensis — Incorrect. This bacterium is a biocontrol agent; its toxin kills caterpillars. It is not a biofertiliser.
NCERT Extract:
Microbes as Biofertilisers – “… Cyanobacteria are autotrophic microbes widely distributed in aquatic and terrestrial environments many of which can fix atmospheric nitrogen, e.g. Anabaena, Nostoc, Oscillatoria, etc. In paddy fields, cyanobacteria serve as an important biofertiliser. Blue green algae also add organic matter to the soil and increase its fertility.”