- Activation of plastid DNA synthesis occurred early in barley leaf chloroplast development. High rates of DNA synthesis were observed in the leaf basal meristem of dark-grown plants where plastid transcription activity was low. DNA synthesis activity decreased in later stages of chloroplast development. Plastid nuclei acid-binding proteins were detected after lithium dodecylsulfate (LDS)-polyacrylamide gel separation and renaturation. One set of nucleic acid-binding proteins was associated with plastid nucleoids. A second set of nucleic acid-binding proteins co-sedimented with ribosomes and most probably corresponds to ribosomal proteins. Changes in the composition of the nucleic acid-binding proteins were characterized as a function of chloroplast development in dark-grown and illuminated barley plants.