The concept of the quiescent centre and how it found support from work with X-rays. II. The molecular aftermath

With the advent of the molecular era of plant biology, the location and activity of the quiescent centre (QC) within the root meristem were reappraised with respect to the transport and distribution of hormones, especially auxin. Later, when methods for probing gene activity became established, the genes and their regulators that were identifiably specific to the QC were also actively studied, at first in relation to the establishment of the root and its QC in the proembryo and later in relation to the interaction of the QC with neighbouring meristem cells. Auxin distribution in and around the QC was found to be associated with co-located oxidative enzymes which established a redox system within the root apex. This system is pivotal in both maintenance of quiescence and the activation of cell proliferation in the QC via the generation of reactive oxygen species (ROS) and their interaction with mitochondria. These and other features of QC biology are summarised.