Fructose-induced dark germination ofAnabaena akinetes

Standard sporulation medium was used to produce akinetes from vegetative cells ofAnabaena variabilis and culturedAnabaena azollae isolated fromAzolla mexicana. Singlecelled, axenic akinetes were incubated on BG-11 medium supplemented with 1% Bacto-agar. Three different sources of combined nitrogen–KNO₃ (5 mM), NH₄Cl(5 mM), and glutamine (5 mM)–were added singly or in combination with fructose (50 mM) to the BG-11 plates. The akinetes were incubated under continuous light (5500 lux) or in the dark at 25±2°C. Akinetes of both species germinated in the dark when BG-11 was supplemented with fructose. Akinetes incubated in the dark on plates containing NH₄Cl and fructose germinated less than those germinated in the presence of fructose alone. Akinetes of both species germinated in the light.