Can anyone explain me this diagram?
Anabaena is a bacteria that comes under the kingdom of Monera which includes prokaryotic organisms. So Anabaena does not have a well-defined nucleus and does not have cell organelles. They have resting spores which are nitrogen-fixing bodies which have thick cell walls. Heterocysts are also present to help fix atmospheric nitrogen using an enzyme called Nitrogenase which acts like a catalyst(A catalyst is something which increases the speed at which a chemical reaction takes place). It is an autotroph as it is capable of nitrogen fixation.