Effect of light on the chloroplast division cycle and DNA synthesis in cultured leaf discs of spinach.

The effects of light on both the division cycle of chloroplasts and the synthesis of chloroplast DNA were investigated in cultured discs taken from the distal end of 2-centimeter spinach (Spinacia oleracea) leaves. Comparisons were made of discs cultured for a maximum of 4 days in a shaking liquid medium under continuous white light, darkness, and of discs cultured for 1 day in light following 3 days in darkness. In continuous white light the shortest generation time of chloroplasts observed in this study was 19.

Nuclear DNA regulates the level of ribulose 1,5-bisphosphate carboxylase oxygenase in Medicago sativa L.

The response to selection for leaf proteins was studied during three selection cycles. Selection for high total nitrogen content showed 75% heritability, and the levels of both ribulose 1,5-bisphosphate carboxylase oxygenase (Rubisco) and cytoplasmic protein were strongly under nuclear DNA control. High and low protein content were correlated with chloroplast area.

Microspectrofluorometric Measurement of Chloroplast DNA in Dividing and Expanding Leaf Cells of Spinacia oleracea.

Absolute DNA amounts of individual chloroplasts from mesophyll and epidermal cells of developing spinach leaves were measured by microspectrofluorometry using the DNA-specific stain, 4,6-diamidino-2-phenyl indole, and the bacterium, Pediococcus damnosus, as an internal standard. Values obtained by this method showed that DNA amounts of individual chloroplasts from mesophyll cells fell within a normal distribution curve, although mean DNA amounts changed during leaf development and also differed from the levels in epidermal chloroplasts. There was no evidence in the data of plastids containing either the high or low levels of DNA which would be indicative of discontinuous polyploidy of plastids, or of division occurring in only a small subpopulation of chloroplasts.

Direct measurement of femtogram amounts of DNA in cells and chloroplasts by quantitative microspectrofluorometry.

Absolute DNA amounts of individual chloroplasts were determined by measuring the fluorescence intensity of chloroplasts stained with 4',6-diamidino-2-phenylindole (DAPI) relative to that of the bacterium Pediococcus damnosus (cerevisiae) smeared on the same slide. An absolute DNA content of 7.7 X 10(15) g for a standard P.

Plastid-DNA levels in the different tissues of potato.

The plastid-(pt) DNA levels in the different tissues of potato (Solanum tuberosum L.), including tubers of differing ages, have been studied. The DNA could be detected as a single nucleoid in amyloplasts of cells from young potato tubers by fluorescence microscopy, following staining of glutaraldehyde-fixed tissue with 4,6-diamidino-2-phenyl indole (DAPI).