Modified plant shoots
Modified shoots, compared with the traditional above-ground plant organs, are able to perform additional functions. Thanks to what features of the structure is it possible?
Features of the structure of escape
Escape is the land part of the plant. Its basis is the stalk. This is the axial part of the shoot, on which the leaves and buds are located. Depending on the location in space, distinguished upright, creeping, climbing, creeping, clinging shoots.
The places of attachment of leaves to the stem are called knots, and the distance between them is called the internode. On the shoot are also embryonic organs, which are called the kidneys. If the leaves develop from them, they are vegetative, and if the flowers are generative.
The aboveground organ of plants performs the function of vegetative propagation. During this process, the multicellular part is split off from the whole organism, due to which its integrity is restored.
An important role played by the shoot in the implementation of growth and regeneration.Due to the presence of chloroplasts in the green plastids, the leaf provides the plant with organic substances that are synthesized during photosynthesis. The resulting carbohydrates are used to carry out various life processes.
Modified underground shoots
But to perform additional functions of the typical features of the structure is not enough. Therefore, in nature often modified shoots. Due to the formation of various thickenings and change in shape, they can store water, as well as nutrients, ensure the viability of plants during an unfavorable period, and occupy an advantageous position in space.
Modifications or metamorphoses of the shoot can develop in the soil or be above ground. The first group includes tubers, bulbs and rhizomes. The above-ground modifications of the shoot are the whiskers, the antennae, and the spines. Consider their structure in more detail.
Well-known onions and garlic are also an underground modification of the shoot. At its base is a flat stem, which is called Donets. On it grows vegetative buds, from which leaves are formed.They are of three types:
The leaves of the first type will perform the main function of the bulb. They store water with solutions of mineral substances. Dry membranous leaves are protected from mechanical damage and adverse conditions. From the vegetative buds of the donut grow young leaves, which are often called green onions.
Bulbs under the ground tolerate drought and frost. So, for example, tulips, crocuses, lilies grow and flourish during a wet and warm season, after which young bulbs are formed underground. They are usually dug up after flowering, stored in a cool place, and planted in late summer.
Why is a tuber a modified shoot?
Many modified shoots grow underground. For example, potato tubers or Jerusalem artichoke. Therefore, they are often confused with another vegetative organ of plants - the root. Proving that a tuber is a modified shoot is very easy. Its thickened part is the stem. It accumulates the starch carbohydrate reserve of plants. The cover cloth of this shoot is the bark. We cut it when we are "peeling potatoes".Another evidence is the presence of kidneys. They are called eyes. In the spring of them develop young shoots.
The rhizome is a modified shoot, which is also located underground. Despite the name, it has nothing to do with the underground organ of plants. The rhizome consists of elongated internodes on which vegetative buds develop. In the spring of them develop leaves. Soil nutrition is provided by the fibrous root system, which grows in bunches.
If you have ever tried to get rid of wheatgrass weed, then you know that this is quite difficult to do. Often tearing leaves out of the soil, we leave the shoot itself with viable vegetative buds, so after a certain time they appear again. The presence of rhizome is typical for lily of the valley, kupeny, mint, iris, asparagus.
Mustache and mustache
And these above-ground modified shoots are often confused because of similar names. In fact, they have different origins, and therefore functions. Whiskers, or stolons, are found in strawberries, strawberries, chlorophytum, and saxifrage. Most often, these are creeping shoots with elongated interstices and a system of adventitious roots. They develop simple leaves.These structures are able to take root and give rise to a new organism. So they carry out sexual reproduction.
Antennae are formed in grapes, grades, peas, beans. They can develop from a stem or leaves. They help climbing plants to hold onto support. As they grow, the antennae, like a spiral, twist around various objects. As a rule, if such structures do not come into contact with the support, they wither and die.
Almost every lover of indoor flowers in the house grows zigokaktus ("Decembrist"). His escape is called cladode. This modification is a flattened stem, which performs the function of the leaves. This is manifested in the fact that cladode performs photosynthesis. Stems origin proves the formation of flowers on it, which are never formed on the leaves. The same modified shoots are found in prickly pears, asparagus, and Smilax.
The meaning of shoot modifications
Metamorphoses of vegetative organs significantly increase the adaptive capacity of plants. Modified shoots perform additional functions in the plant's organism in the form of preserving the reserve of substances and providing an additional method of vegetative propagation.
The man thanks to them gets a large amount of planting material. We eat potato tubers, leek bulbs and garlic, which are rich in carbohydrates, biologically active substances and vitamins. Medicinal infusions are prepared from the rhizomes of valerian and lily of the valley.
The most common modified shoots in nature are the bulbs, tubers, whiskers, antennae and rhizomes.