Growing Point

Growing Point 

the rounded cone-shaped tip of a growing axial organ of a plant (stem or root), which consists of formative tissue (meristem). In algae, mosses, ferns, and horsetails the growing point consists of a single initial cell; in club mosses and seed plants it is made up of groups of initial cells placed in layers parallel to the surface of the organ. As a result of the division of these cells, the corpus, a mass of cells enclosed by a dome-shaped tunica, is formed. The cells of the corpus divide in various directions (volume growth), and the cells of the tunica divide predominantly perpendicularly (surface growth). It is by this process that plant growth occurs.

The growing point is sometimes called the apex, and its terminal cells are known as apical cells. The cells of the growing point that lie at its very tip, which are often designated as the promeri-stem, are converted lower on the axis into the meristem, from which true tissues are formed. At some distance from the tip of the growing point of the stem, or shoot apex, rudimentary leaves arise exogenously in the form of surface nodules. Buds are subsequently formed in the axils of these leaves. The young leaves and the shoot apex form the axillary bud. Between the rudimentary leaves there are zones of intercalary growth, which cause the shoot apex to grow. The growing point of a root, or the root apex, lacks surface appendages and is covered with a rootcap.

O. N. CHISTIAKOVA