Some Observations on the Pattern of Sporulation in a Blue-green Alga, Anabaena doliolum

Sporulation in Anabaena doliolum begins in the middle of thetwo heterocysts and proceeds towards the heterocystous ends.Two inorganic nitrogen sources—potassium nitrate and ammoniumchloride inhibit sporulation, whereas glucose promotes it. Duringsporulation, the reductive ability of the heterocyst graduallydiminishes. It is concluded that spore differentiation in this alga is controlledby critical levels of nitrogen and of sugar in the cell. Thecritical levels are probably regulated by the heterocyst.