Fig. 4. Spatial distribution of mitotic activity over time. (A-C) A reconstructed L1 layer of the same plant separated by 12-hour intervals. Cells that have divided in each of the intervals are differentially color-coded. Red dots represent cells that divided in the first 12-hour window, yellow dots the following 12 hours, and blue dots the final 12 hours. (D-G) Individual optical sections from the same plant, depicting cells located in the L2 and the corpus from the same time point as in (C), and the color code remains the same. The overlapping dots indicate a second round of cell division (arrows). (H-J) Reconstructed views of the L1 layer of the same SAM followed over 72 hours. The total elapsed time is marked in individual panels. Different colored sectors represent regions of primordium development marked as stages in transition from P-2 to P-1, from P-1 to P0, from P0 to P1, from P1 to P2 and from P2 to P3. The numbers expressed as percentages in (J) represent averaged cumulative mitotic index calculated for every 24-hour interval over 72 hours, in sectors representing primordia at the same stages. The numbers in parentheses indicate the number of cell divisions over the total number of cells.