CYTOPHOTOMETRIC STUDY OF NUCLEAR PROTEINS AND NUCLEIC ACIDS IN PARENCHYMATOUS TISSUE OF ORCHID EMBRYO

Quantitative changes in DNA, nuclear RNA and nuclear proteins were investigated during early phases of degeneration in the parenchymatous region of the Vanda embryo by cytophotometric techniques. The results show that the increase in nuclear size which occurs with aging is accompanied by an increase in specific dye binding by DNA, RNA, total nuclear protein, non-histone protein, histones and protein-bound sulfhydryl groups. DNA-Feulgen per nucleus was found to increase in whole-number multiples of the 2C value to 8C; beyond this level the amount of dye bound by DNA increases in unequal fractional multiples of the 2C value. A number of large nuclei were found whose density, in terms of the molecular constituents measured, is greater than would be predicted on the basis of their nuclear volume. These are tentatively interpreted as polyploid nuclei showing incipient pycnosis in which the nucleic acids and nuclear proteins are highly concentrated. © 1969.