Studies of Chloroplast Development in Euglena. V. Pigment Biosynthesis, Photosynthetic Oxygen Evolution and Carbon Dioxide Fixation during Chloroplast Development

Abstract

Our studies with Euglena (2, 6, 14, 19, 20) have suggested that dark-grown cells contain approximately 30 proplastids which develop into about 10 chloroplasts when the cells are exposed to light. The existence of these proplastids, originally inferred from studies on ultraviolet inactivation and photoreactivation of chloroplast formation (14,19), was confirmed by fluorescence and electron microscopy (2, 6). Other workers have studied some of the initial steps involved when dark-grown cells are exposed to light, such as the conversion of protochlorophyll to chlorophyll (17). Other studies also exist of the related problem of the physiology of chloroplast development in higher plants (3, 7, 23, 27). Our earlier work (20) also showed that chloroplast development in Euglena could be separated experimentally into 2 phases: replication of the system which manufactures the chloroplast and development of the proplastid into the mature chlor6plast. In this study we correlate the onset and kinetics of pigment formation, 02 evolution and CO2 fixation with the development of the proplastid into the mature chloroplast. Materials and Methods