Aquatic fern which supports the growth of blue green algae, Anabaena, and used to increase the yield of paddy crop is
A
Salvinia
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B
Marsilea
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C
Isoetes
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D
AzolIa
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Solution
The correct option is D AzolIa Azolla is an aquatic floating fern, found in temperate climate suitable for paddy cultivation. The fern appears as a green mat over water. The blue green Algae cyanobacteria (Anabaena azollae) present as a symbiont with this fern, fixes atmospheric nitrogen.
As green manure, Azolla is grown alone for two to three weeks in flooded fields. Afterwards, water is drained out and Azolla fern is incorporated in the field before transplanting of paddy.
Dry Azolla flakes can be used as poultry feed and green Azolla is also a good feed for fish. It can be used as a bio-fertilizer, a mosquito repellent, in the preparation of salads and above all as a bio-scavenger, as it takes away all heavy metals.