Root Growth at the Cellular Level in Plants of Different Species: Comparative Analysis

Analysis of root growth parameters was carried out on the seedlings of 53 monocotyledonous and 78 dicotyledonous plant species. Daily increases of the root length, the root diameter, the length of the meristematic and elongation zones, the length and the number of cells in a cell file of the meristematical cortex cells, and the length of the fully elongated cells were measured during the steady-state growth. From these parameters, such indices as root growth rate, the relative rates of cell division and elongation, rates of the cell production and transition to elongation, duration of the cell cycle and elongation were derived. Plants from different families were found to have a clear resemblance in the parameters determining the root growth at a cellular level. In the examined species, the difference in the root growth rate depended mainly on the difference in the cell number in a cell file within the meristem and, to a lesser extent, on the length of the cells that had completed growth and on the cell cycle duration. The length of the meristem and the number of meristematic cells in a cell file strongly correlated with the root diameter, whereas the relative growth rate of the meristematic and elongating cells and the duration of the elongation growth had weak correlation with the root diameter.