How does the stem grow in length and thickness?

The stem also increases in length only at the top, where cells are constantly dividing, this zone is also called the growth cone. And the stem grows in thickness due to the numerous division of cells of the educational tissue located under the bark. It’s called cambium. This process can be observed in trees and shrubs.

If you look at the cross section of the stem under a microscope, you can see its four main layers: bark, cambium, wood and pith. The structure of each layer depends on its function. Thus, the thinnest layer, the cambium, consists of educational tissue, the cells of which are constantly dividing. Some of the new cells move towards the bark, and the other part – towards the wood. That is, the function of the cambium is the growth of the stem in thickness. The division stops only in winter. Therefore, in trees of the temperate zone, annual rings are formed – a layer of wood in one season.