Plants grow throughout life, and this ability radically 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 on the tops of the buds, as well as on the apex of the main stem. How do plants manage to keep growing?
Cone of growth: what is it and what is its role?
At the tops of the stem and root of the plant there is a special division zone, which is formed by meristem cells. A feature of this plant tissue is the ability to continuously and rapidly divide, which leads to the growth of the organs of the whole organism in length and thickness.
Educational tissue is also located on the tops of the 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 adnexal. The first are located on the apex of the plant, and theirthe growth point allows the body to grow in length. Lateral buds are located on the trunk and are responsible for branching, that is, the formation of lateral shoots. Adnexal buds are considered dormant and are activated if the meristem at the top has stopped dividing.
What does the growth cone consist of? First, it is formed by meristem cells, which rapidly divide and subsequently determine all other tissues. Secondly, near the growth zone there is a rudimentary stalk, rudimentary leaves and rudimentary bud, which will become the basis for the formation of a young shoot.
Growing cone of stem and root
Educational tissue is concentrated primarily on the tops of the plant, that is, on the apex of the stem and at the tip of the root. The stem, therefore, like the root, increases its length due to the division of mesoderm cells. 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 division process. Therefore, a root cap is located on top of the division zone, the cells of which are exfoliated along with the soil, thereby protecting vulnerable mesoderm cells, and also secrete mucous substances that help to advance the tip of the plant's underground organ.
Meristem - the educational tissue of plants
The tissue that makes up the bulk of the growing cone of buds, stem and root is called "meristem". This educational tissue consists of small thin-walled cells that have a large nucleus and numerous small vacuoles. The function of the meristem is the rapid division and increase in plant biomass.
According to localization, 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.
- The 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, while in perennial woody plants it remains, which makes it possible for the stem and root to grow in width. As a result of the work of the lateral meristem, the so-called growth rings are formed.
The intercalary, or intercalary, 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 isolated, 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, meristems are divided into primary and secondary. The former form the body of the embryo, while the latter are already observed in a young, mature plant.
Use the features of the meristem in practice
Sometimes house or garden plantsbegin to grow rapidly in length, not at all branching into small side shoots. To avoid excessive growth of the stem in height, they resort to cutting off its top. 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 process of growth 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 cone of growth plays a key role in the growth of flora. It is formed by cells of the meristem, or educational tissue, which creates new apical and lateral shoots. The growth cone is located in the buds, which protect the meristem from environmental influences. Actually, any kidney gives rise to a new shoot due to the division of mesoderm cells.
