;Dark-Lethality' of Certain Chlamydomonas reinhardtii Strains Is Prevented by Dim Blue Light.

Cells of certain Chlamydomonas reinhardtii strains dramatically swell and ultimately disintegrate when grown in the dark but not in the light. This effect of darkness is delayed: cells undergo about two divisions before swelling. Measurements on O(2) uptake and ATP content indicate that the cells grown in the dark are not deficient in energy supply. Dim blue light not effective in photosynthesis prevents ;dark-lethality'. Inhibition of protein synthesis during the latent period with cycloheximide also prevents dark-lethality. We propose that blue light stimulates synthesis of one or more proteins which are part of or are important in assembly of an osmoregulatory complex.