The Constancy of Desoxyribose Nucleic Acid in Plant Nuclei

Abstract

For a number of years considerable interest has been centered in the role of nucleic acids in cellular processes. Recently desoxyribose nucleic acid (DNA) has been shown to possess interesting characteristics that have led several workers to consider it an essential component of the gene.'-3 DNA is probably a universal constituent of plant and animal nuclei. Its low turnover rate to radioactive phosphorus and nitrogen, in non-dividing tissues, is evidence for a chemical stability considerably greater than that of other cell components.4 6 Moreover, recent analytic data on the actual amounts of DNA within nuclei have suggested that it possesses a quantitative stability as well.Computations on the amount of DNA per nucleus have been made in two ways. Chemical analyses of large numbers of cells, with the number present estimated by sample counts, have given the average amount of VOL. 36, 1950 643

Genome size variation in Chenopodium quinoa (Chenopodiaceae)

“…Interest in the genome size has been fuelled by the fact that nuclear DNA content can affect various characteristics at the cellular, tissue and organism levels, and can have important ecological and evolutionary consequences (Knight et al 2005). The DNA C-value for a species is the amount of nuclear DNA in the unreplicated haploid genome of a gamete, and it tends to be characteristic of a taxon and quite constant within a species (Swift 1950). However, since the beginning of the 1980s the number of studies showing significant intraspecific variation in genome size has continued to increase and the original view of species-specific constancy has been questioned (Michaelson et al 1991;Reeves et al 1998;Schmuths et al 2004).…”

Increased accuracy and speed of absorption cytometric DNA measurements by automatic corrections for nuclear darkness

“…Swift used off-peak wavelength measurements in 1950 to avoid optical errors in measurements of intensely stained cells and showed consistency of Feulgen absorbances in plant nuclei (19). Glare (9,14,15), diffraction (6, ' 7,121, and residual distributional errors (4,lO) are increased when cells are intensely stained.…”

Nitrogen and Phosphorus Fractions, Respiration, and Structure of Normal and Crown Gall Tissues of Tomato

“…Two days after inoculation there was a peak in the level of DNA with no evidence of cell division about the point of inoculation. The recent work of SWIFT (32) suggested the possibility that there may be a duplication of chromatin in these pre-tumorous cells since in normal plant tissues the DNA per nucleus doubles preceding cell division. As no corresponding change was noted in the wounded control tissues, this increase in DNA may be the first indication of the subsequent burst of cell division noted during the early growth phase.…”

“…The second peak in DNA level of the tumorous tissue is almost certainly due to the large numbers of cells per unit weight of tissue. Measurements of the relative amounts of DNA per normal and tumorous cell nucleus by the methods of SWIFT (32) at the time of the second peak (14 days after inoculation) did not show any significantly higher concentration of DNA in the tumorous cell nucleus as compared to the control (H. H. Swift, unpublished). The histologically observed enlargement and maturation of the tumorous cells subsequent to the growth phase would explain the drop in the DNA level since the number of cells per unit weight of tissue appeared to have decreased after the 14 to 20 day peak.…”