ELEMENTAL GROWTH-RATE AND RIBOSOMAL-RNA TRANSCRIPT MATURATION EXHIBIT THE SAME PATTERN IN INDIVIDUAL TISSUES OF THE MAIZE ROOT APEX

The results of this study show that it is important to distinguish between the rate of cell growth in length at the level of individual cells and the elemental growth rate in various cell files (tissues). The former differs in each particular maize root tissue at a certain distance from the root tip, while, at any given distance from the maize root tip, the elemental growth rate is the same in every tissue. This demonstrates the co-ordinate symplastic cell growth in the maize root apex.Growth trajectories computed from cell length increases are very similar to those obtained directly using [3H]uridine incorporation. Additionally, the decline of silver grain density in nucleoli shows a direct dependence on increasing distance from the root tip. These observations suggest that elemental growth rate and rRNA transcript maturation are closely related and, together with our previous results and data from the literature, suggest that the three-dimensional chromatin organization, DNA and RNA synthesis, and the growth processes are very closely interrelated in the maize root apex. © 1991 Annals of Botany Company.