Which of the following are the part or example of symbiotic mutualistic association?
$I.$ Yeast
$II.$ Rhizobium
$III.$ Mycorrhiza
$IV.$ Oscillatoria
$I$ and $II$
$I$ and $III$
$II$ and $III$
$III$ and $IV$
Nitrogen fixation is
Why are cyanobacteria considered useful in paddy fields ?
Azolla possesses symbiotic association with
Some blue green algae can be used as biofertilizer as they are
How do biofertilisers enrich the fertility of the soil?