The aerial part of plants is called the term "shoot". Its structure is due to the functions performed. Of course, each organ is indispensable and determines the possibility of the existence of a biological species. Nutrition functions, growth processes, adaptability are just some of the most important functions of the visible part of plant organisms.
Biology: Escape Structure
In morphology, the axial and lateral parts of this organ are distinguished: the stem and leaf. The structure of the plant shoots is striking in its diversity: from microscopic water duckweed to giant forest sequoia. It is due to the different structure of the components of the aerial parts associated with the characteristics of the habitat and climatic conditions. There are also shortened embryonic shoots - kidneys.
The place of attachment of the sheet to the axial part is called a node, and the angle that is formed between them is called the sinus. Here are specialized buds that form leaves or flowers. The distance between the two leaf attachment points is called the internode.
Stem
The structure of the shoot initially depends on the direction of growth and location in the space of the stem. Depending on these signs, erect, creeping, creeping, curly and clinging species are distinguished. Diverse stems and the nature of the surface. It can be naked or with outgrowths, smooth or rough. If you cut the stem across, you can determine the shape: round, ribbed, with a certain number of faces or oblate.
Strawberry mustache is also its shoot, having shortened internodes.
Depending on the life form, grassy and ligneous stems are distinguished. The former do not have cambium - lateral educational tissue. In the first years of life, new shoots of trees and shrubs look like them. They are green in color and capable of photosynthesis. Over time, they lignify, becoming more durable. They are able to hold large fruits and withstand strong gusts of wind.
Types of stems
Depending on the characteristics of the development cycle, plants can be one-, two- and perennial. For example, asters fade in the fall, after which they completely die off. Carrots and beets develop differently. In the first year of life, they form root crops, which are organs that store nutrients. In the fall, their stem dies. But the plant exists in the form of a modified stem. With the onset of favorable conditions, the shoot grows again. At the same time, in the second year of life, seeds are formed on it as a result of flowering, with the help of which the plant multiplies.
Let us consider the life cycle of perennial plants, having studied the structural features of shoots of conifers. These are shrubs or trees that have a single powerful stem - the trunk. Its development begins with seed germination. As a result of its growth, a seedling is formed, and after - an adult plant. The life cycle of perennial plants ends with death. Conifers are considered to be true centenarians. So, pine lives for about 400 years, spruce - up to 500, and juniper - as much as 1000!
Sheet
The lateral part of the shoot is no less functional and diverse. It provides air nutrition, transpiration - evaporation of water from the surface, vegetative propagation. The shoot, the structure of which is determined by the functions performed, is characterized by various leaves.
Cactus needles are needed to reduce the amount of moisture evaporated. And the palmate broads of horse chestnut, on the contrary, increase its amount.
Leaves with one plate are called simple, and with several located on one petiole - complex. Looking at them, you can notice a certain pattern. His veins create. These are vascular-fibrous bundles of conductive tissue. According to the nature of venation, leaves with reticulate (maple, apple tree), parallel (corn, rye) and arched (plantain, lily of the valley) venation are distinguished.
Leaf arrangement
The shoot, the structure of which depends on the amount of solar energy received, is characterized by a different arrangement of leaves on the stem. If they are arranged in a spiral, another is formed, and if in a circle - the opposite, or whorled.
In nature, there are no plants that do not renew foliage. Pine and spruce dump it. Since not all leaves fall at once, no one notices this.
Escape Modifications
When it becomes necessary to perform additional functions, the shoots and their components are modified. Leaves can turn into thorns or scales. In plant predators, they are able to capture and digest small insects.
The structural features of the shoot can be considered with the example of a bulb. Its flat, modified stalk is called the "bottom". There are several types of leaves on it: succulent - for storing water and nutrients, dry - for protection. In addition, young green leaves grow from the buds with sufficient water. The fibrous root system also grows from the stem .
Jerusalem artichoke tubers, also called an earthen pear, also form a variation of the shoot - a tuber. On the thickened fleshy stalk there are cicatricial buds from which young shoots grow.
Underground stems with elongated internodes are rhizomes. They are similar to whips, have well-developed mechanical and conductive fabrics. From buds located on the rhizome, leaves are formed. Those who are new to the structural features of rhizomes believe that if you get rid of the leaves, the whole plant will die. But this opinion is erroneous, because the main part of the plant is reliably protected and is underground.
The relationship of structure and function
The structure of the shoot depends on the functions performed. This can be proved by considering the structural elements of its parts. The sheet on the outside is covered with living skin with a skin in which there are holes - stomata. They are necessary for protection and gas exchange. The inner contents of the leaf are represented by the main storage and chlorophyll-bearing tissue, which is responsible for the autotrophic nutrition of the entire plant. Elements of conductive and mechanical tissue, forming veins, are the basis for the transportation of the entire gamut of essential nutrients.
The vegetative organs of the plant are the root (its underground part) and the shoot. The structure of the generative parts does not allow them to perform such functions. They carry out the process of sexual reproduction and distribution of plants. But the flower develops precisely on the stem, and for its development, organic substances formed in the leaves are necessary.
We can conclude that the plant is a single organism, the functioning of parts of which are interconnected.