Which feature of some species of blue-green algae helps promote them as bio-fertilizers?
1
They convert atmospheric methane into ammonia which the crop plants can absorb readily.
2
They induce the crop plants to produce the enzymes which help convert atmospheric nitrogen to nitrates.
3
They have the mechanism to convert atmospheric nitrogen into a form that the crop plants can absorb readily.
4
They induce the roots of the crop plants to absorb the soil nitrates in larger quantities.