Action Spectrum for Developmental Photo-Induction of the Blue-Green Alga Nostoc muscorum.

The dark-grown cyanophyte requires a brief exposure to light from the 650 mmicro region of the spectrum before it can complete its developmental cycle. Induction is reversed by exposure to green light. A blue protein, presumably allophycocyanin (absorption maximum, 650 mmicro) has been demonstrated in aqueous extracts of the cyanophycean cells.