LIGHT INDUCED SYNCHRONIZATION OF ALGAL SPECIES THAT DIVIDE PREFERENTIALLY IN DARKNESS*

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Abstract
Abstract— Three algal species (Protosiphon botryoides, Chlorella pyrenoidosa and Chlamy‐domonas gymnogama) which divide preferentially at night during natural or simulated day‐night conditions are shown to have cell division inhibited by light in the blue region of the visible spectrum (400–500 nm) and stimulated by the remainder of this spectrum (500–730 nm). Synchronous division has been established in cultures of these organisms on a circadian or longer period by alternating fluorescent cool‐white light and cool‐white with the blue component removed. This procedure is suggested as potentially superior to other methods for synchronizing cultures of algae that prefer, in nature, to undergo cell division at night. Where this procedure does not work it is recommended that an action spectrum for cell division be obtained, since this may provide information for achieving optimal synchrony through the use of other specific wavelength regimes.