What is a stem? Structure and significance of the stem

What is a stem? From the point of view of biology, it is part of the plant on which leaves and flowers are located, which is the continuation of the vascular system originating in the roots. The main function of the stem is to deliver water and necessary minerals from the soil to the leaves and other parts of the plant. Green stems are also responsible for nutrition and are involved in photosynthesis.

Stem: its structure and meaning

Fabrics at the end of the stem, capable of dividing cells and causing its lengthening, are called apical meristems. The layers of the stem include the epidermis - an outer layer of cells covered with special plant wax that provides protection from the external environment. Primary tissues bind the epidermis and internal phloem, responsible for the distribution of photosynthetic products throughout the plant. Xylem tissues distribute water and minerals from the roots to the very top, thus providing structural support in the plants. Cambium fabrics are a layer of dividing tissues, their growth allows the trunk to grow in width. The value of the stem is, first of all, in providing the vital substances of the whole plant. If it is damaged or tightly bandaged, then over time, tissues, devoid of nutrition, begin to dry slowly. Complete death occurs with the withering away of the root system. Stem parts also include a core, which in old woody plants is filled with rigid xylem of wood fibers and used to identify plants. It can be solid or hollow. Its cross-section can be round, triangular or in the form of a star.

External characteristics

What is a stalk and how does it look? The top of the stem is its main growth point. The receptors located there can be represented in the form of leaf vegetative buds and reproductive buds. In many plants, the specific apex hormone auxin suppresses the development of the lateral buds, thereby orienting the plant upwards, and not to the side. If the apical bud is removed during pruning, the side buds growing from the axils of the leaves will develop more actively, and the stem will take a bushy shape. As a rule, the top is covered with modified sheets - kidney scales, which serve for protection. The bark is an external protective tissue of woody plants and develops with age.

Vascular system

The vascular system is represented by a network of pipes through which water and nutrients are transported throughout the plant, connecting the roots, stem and leaves. Not all representatives of the flora can boast of this, for example, mosses and algae are fed in a diffuse way. Vascular plants include flowering and schistose plants, as well as ferns. The system consists of two main tissues: phloem and xylem. Xylema is a network of pipes that transports water and minerals throughout the plant. In addition, it also provides a secondary function - structural support, it can be compared with the spine, which helps to keep the vertical position. The texture of the stem often depends on the amount of this tissue, for example, it is very much contained in tree trunks, its colors are much smaller.

Common varieties of stems

1. Wood. This includes vertically growing trees with a relatively large core, as well as shrubs (roses, grapes, blackberries, raspberries).
2. Modified. For example, tulips, lilies and onions have a thickened underground stalk with fleshy leaves. The gladiolus has a short, thickened underground stem with shortened scaly leaves. A compressed rod, with growing leaves and flowers growing above and under the roots, have strawberries, dandelions, African violets.
3. Horizontal. For example, above-ground shoots of strawberries, iris.
4. Curly stems (hops, honeysuckle, beans).
5. Types of stems include also a tuber, for example in potatoes.
6. A hummocky trunk, short and flattened, is found in begonia, dahlias. Unlike tubers that have scattered receptors, tuberous stems have only leaf buds on top.

Functions of the stem

1. It supports the leaves, flowers and fruits, linking them to the roots. In trees and shrubs, the main stem or trunk is characterized by a solid columnar structure.

2. It is a conductor of water, nutrients and products of photosynthesis. Its transport system is arranged in such a way that vertical and lateral movement within the plant organism becomes possible.

3. The ability to conserve water and photosynthetic products is a vital function of the stems of plants such as cacti and palms.

4. The young green stem plays a secondary role in the production of food products through the process of photosynthesis, but in some species (for example, cacti), the rod is the main photosynthetic organ.

5. It serves as a means of asexual reproduction in many plant species, including propagation by cuttings.

Parts of the stem

All stalks of angiosperms, including those that are heavily altered, have nodes, internodes, buds, and leaves. A knot is the point from which leaves or buds grow. The site between them is called an internode. The bud is an embryonic trunk, which has the potential for growth and development. It can grow into a leaf or a flower. Such kidneys are referred to as leaf buds, buds and mixed buds. Many of them remain at rest for a certain period, then grow into separate parts or are built naturally into stem tissues and are barely noticeable. Trees and shrubs, in addition to the main stem, also usually have lateral branches, to which smaller branches are attached. In addition to leaves and buds, there may be other structures in the form of hairs that are outgrowths of epidermal cells, thorns and stipules.

Stem dimensions

When answering the question about what a stalk is, it is important to take into account also its dimensions. Applied to all plants, it is most often an overground part that provides structural support and serves as a mediator and conductor between the root system and leaves. Stems vary in size, starting with a small sprouting of the vine to a 15-meter diameter tree!

Value

What is a stem? We can say that this is the central axis to which all the other parts are attached. In most plants, they are located above the surface, but in some species the stem can be hidden under the ground. Its structure and meaning are inextricably linked. Thanks to the unique structure, water and nutrients are delivered to both leaves and roots. The importance of the stem can not be overestimated, the overlap of this vital artery leads to the death of the plant. There is a large number of industrial applications, including woodworking (logs, firewood, lumber). It is also a rich source of pulp for making paper, some types of stems can be a source of nutrition. Its fibers, when processed, are part of medicines, latex, tannins, paints and much more. Some types of stems are used for asexual or vegetative propagation of plants.

A huge number of applications

There are thousands of plant species whose stems are of great importance for agriculture, for example potatoes. Stalks of sugar cane are the main source of sugar. Maple sugar is obtained from the maple trunks. From vegetables, asparagus stems, bamboo shoots, kohlrabi and walnut are used. Spicy cinnamon is a bark. Gum arabic is a food additive obtained from acacia trunks. Chickle is the main ingredient in chewing gum, extracted from wood chicle. Bamboo is made of paper, furniture, boats, musical instruments, fishing rods, water pipes and even build houses. The cork is obtained from the bark of cork oak. Rattan, used for furniture and baskets, is made from the stems of a tropical palm tree. The earliest example of the use of this important part of the plant is the papyrus, popular in ancient Egypt. Amber is a petrified juice from tree trunks, used for jewelry and can contain the remains of ancient animals. Resins made of coniferous wood are used for the production of turpentine and rosin.