Characteristics of root apical meristem cell population kinetics: A review of analyses and concepts

Abstract

Various conclusions have been reached in the literature concerning the organization of root meristems in terms of cell proliferation and quiescence. In this article the methods used in such analyses are examined in order to assess the validity of the results obtained. Cells in root meristems are clearly heterogeneous in terms of cycle time. The existence of quiescent populations of cells outside the quiescent center, however, is more problematic because (i) it is difficult to define clearly the proximal boundary of the root apical meristem and (ii) present techniques used to measure the size of the proliferative cell fraction are likely to be, in many, if not all cases, highly inaccurate. We have concluded that non-cycling cells, other than those of the quiescent center, do not exist within the meristem proper at the apex of the proliferating angiosperm root.