Question

Read the following features:
(a) Nitrogenase activity in heterocyst cells under aerobic conditions
(b) Mucilagenous sheath covering
(c) Occurrence of photosynthesis in all the cells
Which of the given features is/are correct for a filamentous blue green alga, Nostoc?
a and b
only a​

Answer 1

Answer:

only a is correct answer of your question

Answer 2

Answer:

The correct options are (b) and (c).

Explanation:

• Nitrogen fixation is an anaerobic process due to the high oxygen liability of the nitrogenase enzyme. The presence of oxygen can damage and harm the activity of the nitrogenase enzyme. Hence, the first statement is wrong which says that nitrogenase activity in heterocyst cells under aerobic conditions. Heterocyst cells are specialized cells in blue-green algae where nitrogen fixation occurs due to the presence of nitrogenase.
• The presence of mucilaginous sheath (slime layer) is one of the characteristic features of the cyanobacterial cell. This mucilaginous sheath is present in between the cell wall and plasmalemma of the cyanobacterial cell. This sheath helps in absorbing moisture quickly and also delays dessication.
• Photosynthesis occurs in all the cells of blue-green algae because of the presence of chromatophores in all cells. Chromatophore is the specialized compartment in the cyanobacterial cell’s cytoplasm. This contains all photosynthetic pigments such as chlorophyll, xanthophylls, and carotenes.

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