The organs of flowering plants, the most evolutionarily developed representatives of this kingdom of wildlife, have a fairly diverse structure and functions. The underground part of the plant is called the root, the aboveground part is the shoot. It is the shoot of plants that performs the most important functions: gas exchange, photosynthesis, transpiration, vegetative propagation and its optimal location with respect to the sun.
Origin of escape
In the process of evolution, this organ appears in the first natives of the land - riniophytes. Its stems were creeping and forked forks, since mechanical tissues were still poorly developed. But even with such a primitive structure, the photosynthetic surface increased, which means that the plant body was better provided with carbohydrates.
What is plant escape
Escape is the aerial part of the plant, consisting of a stem and leaves. All these organs are vegetative, providing growth, nutrition and asexual reproduction.
The plant shoot also contains the embryonic organs - the kidneys. There are two types of buds: autonomic and generative. The first type consists of a rudimentary stem and leaf, on top of which is an educational tissue (meristem), represented by a growth cone. If, in addition to the stem and leaves, the bud contains the rudiments of flowers or inflorescences, it is called generative. In appearance, such kidneys are distinguished by larger sizes and a rounded shape.
The place to which the leaf is attached to the stem is called a node, and the distance between the nodes is called an internode. The angle between the stem and the leaf is called the sinus.
In the process of development, organs responsible for generative (sexual) reproduction appear on the shoot: flower, fruit, and seed.
Kidney escape development
With the onset of favorable conditions in spring, the cells of the meristem of the growth cone begin to actively divide. Shortened internodes increase in size, resulting in a young shoot of plants. At the very top of the stem are the apical buds. They provide plant growth in length. The axillary and accessory kidneys are located in the sinus of the leaf or on the internodes, respectively. Due to them, the stalk forms lateral shoots, i.e., branches.
Methods of branching plants
Depending on the structure, there are several ways of branching shoots:
- Dichotomous . The most primitive type of branching, in which two develop from one growth point, two from each of them, etc. So some algae and higher spore plants grow: clowns and ferns.
- Primopodial . Such branching can be seen both in gymnosperms (pine, spruce) and angiosperms (oak, maple). For a long time, the stem of these plants grew in length with the subsequent formation of lateral branching.
- Sympodial. With this method, apical growth, on the contrary, is suspended. And the side buds are actively growing, forming more and more side shoots. Pear, cherry and other flowering plants are a typical example of this type of growth.
Modifications of shoots
What is the shoot of plants and how it looks, of course, everyone knows. But environmental conditions often require additional functions. This is easily provided by the organs of flowering plants. The shoot is modified, acquiring new structural features, while it consists of parts of a standard shoot.
The main modifications to the escape include:
- Rhizome - located underground, where it most often grows horizontally. It has elongated internodes and buds, of which leaves appear on the surface of the earth in a favorable period. Therefore, it is very difficult to get rid of plants with rhizomes (lily of the valley, wheatgrass, valerian). After tearing off the leaves, the shoot itself remains in the ground, growing larger.
- Tuber - a thickened internode with kidneys - eyes. The most striking representative of the plants forming the tubers is potatoes. Since it grows in the ground, it is often confused with a modified root. However, there are also elevated tubers, for example, kohlrabi.
- Bulb is a modified shoot of plants with well-developed leaves located on a flat stem - the bottom. Characteristic for garlic, onion, tulip, lily. Nutrients accumulate in the inner juicy leaves, and the outer dry leaves protect them from damage.
- Spines - a protective device for pears, sea buckthorn, hawthorn and other plants. Being in the bosom of the leaf, they reliably protect the plant from animals that want to feast on them.
- Antennae are modified twisted shoots that fix plants in a certain position. Cucumber, grapes, pumpkin - the most common plants using this device.
- Mustache - thin shoots with long internodes. Strawberries and strawberries reproduce vegetatively with the help of a mustache.
As you can see, the shoot of plants consists of parts that are functionally interconnected, can vary depending on environmental conditions and give each plant its own unique look.