Acridine orange (AO) and ethidium bromide (EB) staining of living, dying and dead cells in Vicia faba root meristem cells in relation to (A) the localization in particular zones, and (B-D) the surface area occupied by the cells in particular zones.

(A) Fluorescence picture of AO/EB stained V. faba roots in planta. (a) schematic figure presenting the outline of the roots of the control series, with marked (I) root cap, (II) zone of cell division i.e. root meristem, (III) zone of elongation, and the quiescent center. (b) the control roots, (c) the roots treated with 2.5 mM hydroxyurea (HU) for 32 h, (d) the roots treated with 2.5 mM HU for 24 h and then co-treated with 2.5 mM HU and 5 mM caffeine (CF). Scale bar = 1 mm. The schematic outline of the root from scheme (a) was placed over a root from the control series (b) on which the root outline from figure 'a' and figure 'b' are precisely overlapped, (c) a root from the series, in which seedlings were subjected to replication stress and (c) a root that was induced to premature chromosome condensation (PCC). (c-d) The continuous line marks those root fragments that in terms of size and shape were the same as the analogous areas in the roots of the control series (a-b versus c-d), while the broken line (in figures [c] and [d]) marks the root areas that indicated the appearance of aerenchymatic-like spaces that had formed in the roots that had been subjected to treatment with HU (c) or co-treated with the mixture of HU/CF (d). In places indicated by broken lines, roots of the series (c) and (d) were distinctly wider than the control (b). (B-D) quantitative presentation of surface area (%) occupied by the green, yellow-orange and red colors (that correspond to the populations of living, dying and dead cells, respectively) in the particular zones of V. faba roots. (B) quiescent center, (C) zone of cell division, i.e. root meristem, marked also as zone II, and (D) zone of elongation, marked as zone III.