A pulse labelling experiment was used to study the mitotic cell cycle of proliferating cells throughout the root meristem of
Zea mays
. Seventeen different regions were identified within the area of proliferative activity, extending from the initial cells of the cap columella up to the stele, cortex and epidermis 1000 μm from the cap-quiescent centre junction, and the data were analysed for each region separately. The analyses were made in terms of a mathematical model for cell proliferation and yield statistically efficient estimates of the cell-cycle parameters. The validity of the model is discussed in some detail. It appears that the main difference between the regions studied is in the mean duration of
G
1
, that is, the average delay a newborn cell experiences before it begins to synthesize DNA. The mean durations of
S
and
G
2
, the DNA-synthetic and post-DNA-synthetic phases of the mitotic cycle, are relatively constant. The one exception to this pattern is the quiescent centre; this region includes a relatively high proportion of slowly dividing and non-proliferating cells.
Redox Changes During the Cell Cycle in the Embryonic Root Meristem of Arabidopsis thaliana
