Quiescent centre

The Quiescent Centre is a group of cells, up to 1,000 in number, in the form of a hemisphere, with the flat face toward the root tip. It is a region in the apical meristem of a root where cell division proceeds very slowly or not at all, but the cells are capable of resuming meristematic activity should tissue surrounding them be damaged. Cells of root apical meristems do not all divide at the same rate. Determinations of relative rates of DNA synthesis show that primary roots of Zea, Vicia and Allium have quiescent centres to the meristems, in which the cells divide rarely or never in the course of normal root growth (Clowes, 1956a, b). Such a quiescent centre includes the cells at the apices of the histogens of both stele and cortex. Its presence can be deduced from the anatomy of the apex in Zea (Clowes, 1954), but not in the other species which lack discrete histogens.