A New Type of “Light Inhibition”, Occurring in Synchronous Cultures of Chlorella

Summary

Synchronous cultures of Chlorella partially lovse their capacity of dry matter production and daughter cell formation after irradiation with weak white light during the dark period of the light-and-dark cycle. This effect can as well be saturated by red light (660 mμ), and by serial short exposures to white light or to red light down to 2 min per hr irradiations. The effects of red disturbance light are at least in part reversible by 730 mμ light.

The disturbance light reaction, as we would like to call the phenomenon in question, is probably mediated by the phytochrome system which was not known to be present in algae of the Chlorella type.

The decreased yields of the cultures which are due to exposures to disturbance light can be explained as a presetting of the “physiological clock”. As a result of this presetting the phase of intense substance production ceases too early and the final yield remains comparatively low.

The authors express their gratitude to the Deutsche Forschungsgemeinschaft for financial support of this work.