The Quiescent Centre (QC) is a group of cells located at the root apical meristem of plants. It plays a vital role in maintaining the stem cell population by regulating the rate of cell division and differentiation. The cells of the quiescent centre are characterized by specific features, which are discussed below.

Light Cytoplasm and Small Nuclei
The cells of the quiescent centre have a light cytoplasm and small nuclei. This is because they are not actively dividing and synthesizing proteins and other macromolecules. The low metabolic activity of these cells ensures that they do not consume much energy and resources, which are instead used by the actively dividing cells.

Irregular Cell Division
Unlike the other cells in the root apical meristem, the cells of the quiescent centre do not divide regularly. Instead, they divide infrequently and only when necessary to maintain the stem cell population. This ensures that the number of stem cells is maintained at a constant level, which is essential for proper root growth and development.

Role in Stem Cell Maintenance
The quiescent centre plays a crucial role in maintaining the stem cell population by regulating the rate of cell division and differentiation. It does this by secreting signaling molecules that promote or inhibit cell division, depending on the needs of the meristem. For example, when the stem cell population is low, the quiescent centre secretes cytokinins, which stimulate cell division and promote the formation of new stem cells.

Conclusion
In conclusion, the cells of the quiescent centre are characterized by a light cytoplasm and small nuclei, irregular cell division, and a crucial role in stem cell maintenance. These features ensure that the stem cell population is maintained at a constant level and that the root apical meristem can continue to grow and develop properly.