Action Spectra and Nucleic Acid Metabolism in Circadian Rhythms at the Cellular Level

Abstract

Unicellular organisms exhibit a remarkable similarity to higher plants and animals in their common possession of circadian rhythmicity. This functional similarity, evident especially from observations of Euglena [1, 2], Oedogonium [3], Gongaulax [4], Neurospora [5], and Paramecium [6, 7] has led to the working hypothesis that the underlying structural mechanism of circadian timekeeping is within the living cell. A corollary hypothesis is that every two-envelope cell possesses the capacity for circadian timekeeping as an essential part of its organization. Levels of organization subordinate to that of the typical two-enveloped cell (viz., one-envelope systems such as bacteria and actinomycetes, and molecular systems [8]) have thus far failed to show any such inherent capacity. Against this background, while the descriptive approach continues on many organisms and in many laboratories, the more difficult analytical approach in the form of the application of physical and chemical techniques to cell populations has only begun. Our...