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Updated: Mar 23, 2026

Observation of Photobehavior in Chlamydomonas reinhardtii
Published on: May 6, 2022
PHOTOINDUCTION AND PHOTOREVERSAL OF THE NOSTOCACEAN DEVELOPMENTAL CYCLE(1)
1Microbiological and Biochemical Center, Syracuse University Research Corporation, Syracuse, New York.
Abstract:
The developmental cycle of Nostoc muscorum, a nitrogen-fixing blue-green alga, is controlled by the spectral quality of illumination. Red light with peak activity at 650 mμ induces development of filaments from a nonfilamentous (aseriate) stage of the life cycle. Red-light photoinduction is reversed by simultaneous or subsequent exposure to light from a broad band in the green region of the spectrum. Photo-reversibility of the red-light induction, by green light, decays very slowly, remaining at an appreciable level for over 24 hr after the primary stimulus. Allophycocyanin is indicated to be the photoreceptor for red-light induction. One or more phyco-erythrins may operate as photoreceptors for reversal of induction. The dosage response and wavelength dependence of developmental photocontrol in Nostoc muscorum A indicate that a nonphotosynthetic mechanism is involved in both developmental photoinduction and its photor ever sal.
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