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Question
A water-fern, which is used as a green manure in rice fields, is___________
A water-fern, which is used as a green manure in rice fields, is___________
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Solution
The correct option is D Azolla
- Azolla is a heterosporous pteridophyte. It contains, as an endosymbiont, Anabaena azollae, a nitrogen-fixing cyanobacterium (Nostocaceae family). For many centuries, Azolla has been used in southern China and northern Vietnam as green manure for rice. Azolla in association with blue-green alga Anabaena can fix atmospheric nitrogen (N) into ammonia which can be utilized by rice plants when it is incorporated into the soil.
Therefore, the correct answer is option D.
- Azolla is a heterosporous pteridophyte. It contains, as an endosymbiont, Anabaena azollae, a nitrogen-fixing cyanobacterium (Nostocaceae family). For many centuries, Azolla has been used in southern China and northern Vietnam as green manure for rice. Azolla in association with blue-green alga Anabaena can fix atmospheric nitrogen (N) into ammonia which can be utilized by rice plants when it is incorporated into the soil.
Therefore, the correct answer is option D.
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