Correct Answer - B
Azoespirilllum is a nitrogen fixing bacterium in paddy fields. It is very useful soil and root bacterium. It is associative symbiotic `N_(2)` fixing bacteria. When it is added to the soil, it multiplies in millions and can supply 20-40kg of nitrogen per hectare per season. It also producess growth promoting substanes like indole acetic acid (IAA), Gibberellins `(GA_(3))` and promotes root proliferation. these substances improve the plant growth and yield.
