| Abstract: | The amounts of chloroplast DNA and nuclear DNA in the cellsof spinach leaf discs cultutred under different light regimeshave been measured. The cellular level of ctDNA increased 10-foldin discs cultured in white light and was accompanied by a 2-foldincrease in the cellular level of nuclear DNA. In low intensitygreen light the cellular level of ctDNA increased 6-fold butwas not accompanied by an increase in the level of nuclear DNA.No net DNA synthesis on a per cell basis occurred in discs culturedin darkness. Chloroplasts of uncultured leaf discs containedan average of 83 plastome copies. The number of plastome copiesper chloroplast after 6 days culture decreased to 36 copiesin darkness, remained almost constant at 73 copies in whitelight and increased to 215 copies in low intensity green light. These results suggest that ctDNA replication can be independentof cellular levels of nuclear DNA and chloroplast division. |
