Two-wavelength cytophotometry: the choice of the wavelengths from a practical point of view.

Methods in use for the choice of the two-wavelengths and the effect of a faulty choice of the two wavelengths in the two-wavelength cytophotometric method of Patau and Ornstein are studied by means of a computer simulation and in practice upon pararosaniline-Schiff stained nuclei. A simplification of the measuring strategy is proposed without affecting the accuracy.

Gibberellic-acid-induced cell elongation in pea epicotyls: Effect on polyploidy and DNA content.

In gibberellic-acid(GA3)-treated epicotyls of dwarf peas (Pisum sativum L.) grown in the light, DNA (per cell and per epicotyl) is followed. Histofluorometric DNA determinations show that GA3-promoted cell elongation is not accompanied by increased endomitosis, but chemical estimations show an increased DNA content per epicotyl.

Factors affecting the estimation of the relative amount of chromophore and chromophore area by the two-wavelength method of Patau and Ornstein.

Factors influencing the calculation of the relative amount of chromophore and the chromophore area by the two-wavelength method are examined. The study was carried out with the help of models and further tested on Feulgen stained preparations. Except for certain restrictions the difference between the chromophore area as calculated from the two transmissions measurements and the chromophore area obtained by planimetry can be used as a guide for determining the proper measuring conditions, including the choise of the two wavelengths.

Absorption cytophotometry: evaluation of three methods for the determination of DNA in Feulgen stained nuclei.

Three methods for the evaluation of the relative amount of DNA per nucleus by absorption cytophotometry are compared. A combination of the two-wavelength method (Patau, 1952; Ornstein, 1952), the one-wavelength two-area method (Garcia, 1965) and the determination of transmission through nuclear plugs is proposed in order to estimate systematic errors made by absorption cytophotometry.