2.3. Feulgen DNA Staining

Roots excised from 5-day-old V. faba seedlings were fixed in ice-cold Carnoy’s solution (absolute ethanol and glacial acetic acid; 3:1, v/v) for 1 h, washed several times with ethanol, then rehydrated and hydrolyzed in 4 M HCl (2 h). The staining procedure with pararosaniline (Schiff’s reagent) was performed according to the standard method (e.g., [24]). After rinsing in SO₂–water (3 times) and distilled water, RAMs (1.5 mm long) were cut off, placed in 45% acetic acid, and squashed onto Super-Frost microscope slides. Following freezing using dry ice, coverslips were removed, and the dehydrated slides were mounted in Canada balsam.

To evaluate mean values of mitotic indices and to quantify the occurrence of cells with aberrant chromosome structures, 10,000 Feulgen DNA-stained cells (taken from 10 root meristems) were analyzed for each individual mean value.