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Question
Nitrogen fixation by Nostoc / Anabaena takes place in
Nitrogen fixation by Nostoc / Anabaena takes place in
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Solution
The correct option is D Heterocysts
Heterocysts are specialized nitrogen-fixing cells formed during nitrogen starvation by some filamentous cyanobacteria, such as Nostoc and Anabaena. They fix nitrogen from the air using the enzyme nitrogenase. Nitrogenase is inactivated by oxygen, so the heterocyst must create a micro anaerobic environment. Certain heterocyst-forming bacteria can differentiate into spore-like cells, called akinetes or motile cells, called hormogonia, making them the most phenotypically versatile of all prokaryotes. Once a heterocyst has formed it cannot revert to a vegetative cell. The akinetes are filled with food reserves and have a normal cell wall surrounded with 3 layer coat. Hormogonia are motile filaments formed during asexual reproduction. Cyanobacteria differentiate into hormogonia when exposed to an environmental stressor when placed in new media.
Heterocysts are specialized nitrogen-fixing cells formed during nitrogen starvation by some filamentous cyanobacteria, such as Nostoc and Anabaena. They fix nitrogen from the air using the enzyme nitrogenase. Nitrogenase is inactivated by oxygen, so the heterocyst must create a micro anaerobic environment. Certain heterocyst-forming bacteria can differentiate into spore-like cells, called akinetes or motile cells, called hormogonia, making them the most phenotypically versatile of all prokaryotes. Once a heterocyst has formed it cannot revert to a vegetative cell. The akinetes are filled with food reserves and have a normal cell wall surrounded with 3 layer coat. Hormogonia are motile filaments formed during asexual reproduction. Cyanobacteria differentiate into hormogonia when exposed to an environmental stressor when placed in new media.
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