Plants grow throughout life, and this ability fundamentally distinguishes them from animals. The main role in the formation of new shoots is played by the growth cone - a special structure, the cells of which are constantly dividing. This zone is located at the tops of the kidneys, as well as at the apex of the main stem. How do plants manage to grow constantly?
Rising cone: what is it and what is its role?
At the top of the stem and root of the plant is a special division zone, which is formed by meristem cells. A feature of this plant tissue is the ability to continuous and rapid division, which leads to the growth of organs of the whole organism in length and thickness.
Educational tissue is also located on the tops of green kidneys. Actually, for this reason, new shoots appear from them, which allow the plant to spread over a large area and receive more solar energy for photosynthesis. There are three types of kidneys: apical, lateral and adnexa. The first are located at the apex of the plant, and their growth point allows the body to grow in length. The side buds are located on the trunk and are responsible for branching, that is, the formation of side shoots. The adnexa are considered dormant and are activated if the top of the meristem has ceased to divide.
What does the growth cone consist of? Firstly, it is formed by meristem cells that rapidly divide and subsequently determine all other tissues. Secondly, near the growth zone there are an embryonic stem, embryonic leaves and an embryonic bud, which will become the basis for the formation of a young shoot.
Stem and root growth cone
Educational tissue is concentrated primarily on the tops of the plant, that is, on the apex of the stem and on the tip of the root. The stem, thus, like the root, increases its length due to cell division of the mesoderm. The latter, in turn, in the process of determination form new types of cells and tissues. In the stem, these are conductive tissues (phloem and xylem), the main tissue, integumentary, etc.
The root growth point has its own characteristics. Since it is located at the end of the root and is responsible for its growth in length, solid soil could quickly destroy the thin walls of the cells of the educational tissue, which would stop the process of division. Therefore, a root cap is located on top of the division zone, the cells of which exfoliate together with the soil, thereby protecting vulnerable mesoderm cells, and also secrete mucous substances that help advance the tip of the plant’s underground organ.
Meristem - educational tissue of plants
The tissue that makes up the bulk of the cone of growth of the kidneys, stem and root, has the name "meristem". This educational tissue consists of small thin-walled cells that have a large nucleus and small numerous vacuoles. The function of the meristem is the rapid division and increase in the biomass of the plant.
According to the localization, the meristems are divided into apical, lateral and intercalary.
- Apical meristems are located at the tops of the stem and root. Their main task is to increase the length of the plant.
- Lateral educational tissue is represented by a cambium ring in the stem and a pericycle in the root. In herbaceous plants, this meristem quickly disappears, and in perennial woody plants, it remains, which makes it possible to grow the stem and root in width. As a result of the operation of the lateral meristem, the so-called annual rings are formed.
- The interstitial, or intercalar, meristem is located in the area of nodes of herbaceous plants. This type of educational tissue is best manifested in the cereal family, as it is responsible for the growth of internodes in length.
Wound meristems are also distinguished, which are formed at the site of mechanical damage to the plant body by despecialization of nearby tissues (most often parenchyma).
According to the time of occurrence of the meristem are divided into primary and secondary. The former form the body of the embryo, while the latter are already observed in the newly formed plant.
Using the features of the meristem in practice
Sometimes home or garden plants begin to quickly increase in length, not branching into small side shoots at all. To avoid excessive growth of the stem in height, they resort to cutting its tops. As a result, the growth cone disappears, and the plant begins to branch actively due to lateral and intercalary buds.
If, on the contrary, it is necessary to extend the growth process in length, it is impossible to cut off the top of the stem in any case. This will lead to the loss of educational tissue, which is responsible for the increase in the body of the plant.
Conclusion
The growth cone plays a key role in the growth of flora representatives. It is formed by the cells of the meristem, or educational tissue, which creates new apical and lateral shoots. The growth cone is located in the kidneys, which protect the meristem from environmental influences. Actually, any kidney gives rise to a new shoot due to cell division of the mesoderm.