Studies of chloroplast development in Euglena II. Photoreversal of the U.V. inhibition of green colony formation

Abstract

The inhibition of chloroplast formation in u.v. irradiated progeny of Euglena gracilis can be reversed by visible light with efficiencies approaching 100%. If the cells are permitted to divide after u.v. treatment, photoreactivability is rapidly lost. The kinetics of this loss are fairly consistent with the hypothesis that entities responsible for chloroplast formation are prevented from being replicated by u.v. light and are diluted out among the progeny. There is no decay of photoreactivability in non-dividing cells. The action spectrum for photoreactivation of chloroplast formation shows a single broad peak in the near-u.v. region of the spectrum clearly separating this phenomenon from the light induction of chloroplast formation which has effectiveness peaks in the blue and red regions of the spectrum. The evidence presented is consistent with the hypothesis of cytoplasmic entities which are replicated at cell division and which control chloroplast formation.