Light-stimulated synthesis of chloroplast DNA

Light-stimulated chloroplast DNA synthesis was studied during chloroplast development in the absence of cell division and nuclear DNA synthesis. Incorporation of 32Pi was stimulated 10-15 fold, however, the ratio of chloroplast DNA to nuclear DNA remained constant. Isotope dilution experiments suggested that stimulated labeling of chloroplast DNA represented more efficient utilization of exogenously supplied Pi rather than stimulated turnover of chloroplast DNA. The low level of DNA synthesis and chloroplast development were resistant to nalidixic acid which inhibits semiconservative replication of chloroplast DNA.