Modifications of underground shoots and roots. How to prove that a tuber and bulb are a modified shoot? Thanks in advance What organ is the onion bulb modified from?

A tuber is a part of a plant that is its modified organ. It is necessary for the body to perform additional functions. The features of its structure and varieties of tubers of various origins will be discussed in detail in this article.

Purpose of modifications

The underground and aboveground organs of plants are, respectively, the root and shoot. These vegetative parts serve for air and soil nutrition, as well as for asexual reproduction. But in certain conditions, additional functions are needed for the adaptation process and increased vitality. For these purposes, modifications are needed. The tuber is a prime example of one of them.

A good example of modification of an underground plant organ is root vegetables. They are formed in carrots, beets, radishes, radishes. This is a thickening of the main root in which water and nutrients are stored. Man uses them for food and how

Escape modifications

Tuber and rhizome are modifications of above-ground organs. There is nothing surprising about this. Despite their location underground, they have all the parts of a shoot in their structure. Examples of these are tubers, bulbs, rhizomes, tendrils and tendrils. Each of them has its own structural features that determine their functions. For example, strawberry tendrils are necessary for vegetative propagation. Although it produces flowers and seeds, this method is the most essential. But the mustache of the grape is needed to attach its vines to the support.

A leek or garlic bulb consists of a flat stem called a stem. They attach to it They grow in a bunch. This is a typical structure for At the bottom there are also buds and several types of leaves. Some of them are juicy and meaty. They store water and nutrients. Others are dry and dense, serving as additional protection from mechanical damage and excessive transpiration. Young green leaves periodically grow from the buds located on the bottom. They are commonly called green onions. All of the listed structural features once again prove that the bulb is a modification of the shoot.

Tuber structure

The next example of modification of above-ground organs is the tuber. It is typical for potatoes, Jerusalem artichoke, and kohlrabi. A tuber is the result of thickening of the internodes of the stem, which can be either sub- or above-ground.

Its basis is a thickened stem, rich in starch and other substances. From adverse conditions environment it is protected by the bark. This is what we peel off when we use potatoes for cooking. The thickened stem also contains buds. They are called ocelli. With their help this plant is carried out. In spring, young shoots emerge from the buds, forming a bush and new tubers.

Root tuber

Not only shoots are able to form tubers. Underground part plants are no exception. So, the root tuber is characteristic of dahlia, sweet potato and chistyak. It is nothing more than a thickening of the accessory components. Despite their different origins and locations, such modifications perform exactly the same functions.

Functions

The main purpose of both stem and root tubers is to store water with nutritious mineral and organic substances dissolved in it. Everyone knows how rich in starch potatoes are. It is in its tubers, in the cells of the storage main tissue, that plastids (leukoplasts) containing carbohydrates are located. In this form, plants that have these changes easily tolerate unfavorable conditions, surviving them underground.

Another important function of this modification is the implementation of vegetative propagation. To grow potatoes, it is enough to cut the tuber into several parts, each of which should have buds - eyes, and plant them in the ground. This plant has fruits that can form seeds. But their number is small. Since potatoes are of great economic importance, plant breeders have attempted to develop new varieties with more seeds. But the vegetative method of propagation using tubers turned out to be more productive.

Because the tuber is a storehouse nutrients, such modified elements are used for food. And Jerusalem artichoke can, with constant use, reduce blood glucose levels. Doctors recommend it to people suffering diabetes mellitus. Eating potatoes provides the body not only with the necessary daily carbohydrate content, but also with valuable microelements, such as phosphorus and potassium.

Thus, tubers are modifications of a shoot or root and serve to store nutrients and vegetative propagation. They are of great food and economic importance.

Modifications are associated with the performance of special functions (these are sudden, hereditary changes). The most common modified shoots are rhizomes, tubers, and bulbs growing in the ground. They store reserve nutrients necessary to withstand unfavorable conditions and serve for natural vegetative propagation.

Rhizome

occupy a horizontal position in the soil. It usually has scale-like leaves and buds. Adventitious roots extend from it. Reserve nutrients are deposited in the stem part of the rhizome. It looks like a root, but differs from it in underdeveloped leaves and the absence of a root cap. It contains reduced leaves in the form of brown or colorless scales, and in their axils there are buds from which above-ground shoots grow. They have nodes and internodes; adventitious roots are formed from the nodes. At the top there is an apical bud, due to which the rhizome grows in length. Plants with branching rhizomes grow quickly (creeping wheatgrass, lily of the valley, iris, kupena, etc.). The lifespan of rhizomes ranges from 2-3 to several decades. Thin, elongated underground shoots bearing a tuber or bulb at the top, are called stolons.

Tuber

- this is a shoot with a very thickened stem in which reserve nutrients are deposited. Tubers can be underground or aboveground: Underground - develop on stolons (potatoes, earthen pears). Aboveground - develop in kohlrabi cabbage and some orchids. The tuber has eyes - depressions in which the buds are located. They are arranged on the tuber in a spiral (like leaves on a stem) and give rise to above-ground shoots. The outside of the tuber is covered with epidermis, which is subsequently replaced by a cork. In potatoes, the cells of the tuber pulp are filled with starch, and in the earthen pear - inulin (a complex carbohydrate). Tubers develop from the apical buds of stolons.

Bulb

- underground shoot with a shortened stem at the bottom. Adventitious roots extend down from the bottom, and closely spaced succulent leaves (bulb scales) extend upward, in which reserve nutrients are deposited. In the axils of the bulbous scales there are buds, from which above-ground shoots and new bulbs are formed. The outer dry scales protect the inner fleshy ones from drying out and rotting. Bulbs are formed in onions, garlic, lilies, etc. At the top of the bottom there is an apical bud, which gives rise to an above-ground shoot - a flowering “arrow” and leaves. Bulbs help the plant survive in unfavorable conditions and are an organ of vegetative propagation.

Conclusion:

1. Tuber, bulb, rhizome are modified shoots, because they have buds, shortened internodes, a large reserve organic matter, no chlorophyll, i.e. with their structure they repeat the structure of aboveground shoots.

Modified shoots are a kind of storeroom where nutrients containing starch, sugar, minerals, and phytoncides (substances that kill microbes) accumulate. They are widely used as human food and used as animal feed. In addition, they also have great biological significance - they are all organs of natural vegetative reproduction that occurs in nature without human intervention.

My project clearly shows the structure of the onion bulb. First, I'll tell you about him.

Root system of bulbous and corms of flowering plants consists of adventitious roots of various shapes, formed from the bottom of the bulb or the base of the corm.

For example, narcissus and whiteflower have thick cord-like roots, crocus have hair-like roots. The roots can be branched, like those of a scilla, or unbranched, like those of a daffodil and snowdrop. In addition to adventitious roots, bulbous plants have elongating, or contractile, roots, which usually develop in young plants in the first 2-3 months (in seedlings).

They are located close to the soil surface and serve the plant to burrow into the soil. Retracting roots do not branch, lack root hairs and grow straight down. The cells of these roots contain a lot of glucose, which is quickly absorbed by growing plants, as a result of which the fleshy part of the root becomes flabby and contracts in the longitudinal direction, drawing the bulb or corm deeper.

Scales are modified underground leaves. The scales of the bulb contain reserves of water with sugar and other substances dissolved in it.

In annuals and all corms, the roots are replaced annually (candyk bulb, hazel grouse bulb, crocus corm). In some perennial bulbs, the root system is also replaced annually after the death of the above-ground parts, which are formed again only in the fall (scilla, chionodox, etc.). When developing technology for growing bulbous and corm plants, the characteristics of the root system, the timing of death and the formation of new roots are taken into account.

Bulb is a shortened underground shoot, when the stem is represented by a bottom on which fleshy scales appear. The bulb serves to accumulate reserve nutrients, which are concentrated in its fleshy scales.

Why is a bulb a modified shoot?

Tuber, bulb, rhizome are modified shoots, because they have buds, shortened internodes, a large supply of organic matter, no chlorophyll, i.e. with their structure they repeat the structure of aboveground shoots.

Modified shoots are a kind of storeroom where nutrients containing starch, sugar, minerals, and phytoncides accumulate. They are widely used for human food and used as animal feed. In addition, they also have great biological significance - they are all organs of natural vegetative reproduction that occurs in nature without human intervention.

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The escape is one of the main vegetative organs higher plants. It consists of a stem on which buds and leaves are located. The escape is the most variable appearance structural element of a plant. Modified Escape is a plant organ in which the shape and function of the stem, buds and leaves are irreversibly changed in the process of evolutionary adaptations to certain conditions of existence of the organism. In cultivated plants, shoot modification is caused by human intervention.

Metamorphoses of the shoot can be either minor or significant - up to greatly changed plant forms. Both main and lateral shoots, as well as buds and leaves, undergo metamorphosis.

The main types of green plant shoots are: aboveground and underground. Aboveground (aerial) shoots are assimilative, along the axis of which the leaves are located. Assimilating shoots are very diverse in appearance. In many cases, in addition to the main function of photosynthesis, such shoots perform the role of a storage and supporting organ of the plant, as well as the function of vegetative propagation.

To modifications of aboveground shoots include spines, antennae, cladodes, phyllocladies. In some cases, not the entire shoot of a plant changes, but only its leaves, and the metamorphoses are externally similar to those of the shoot as a whole (antennae, spines).

The thorn is a lignified shortened shoot without leaves with a sharp tip. The role of spines originating from the shoot is mainly protective. The wild apple tree, laxative buckthorn, and wild pear have such spines. In honey locust, thick branched spines appear on the trunks from dormant buds. Hawthorn spines are also formed from the axillary buds of the leaves and are located where the side shoots of other plants are located.

A tendril is a shoot of a metameric structure without leaves, having a rope-like shape with or without branches. Thanks to the presence of stem tendrils, the plant receives additional support. The straightened section of the tendril without branches is the first internode of the axillary shoot, and the twisted, thinner section is a modified leaf. Tendrils develop in plants that are not able to stand upright on their own. Blue passionflower, grapes, and many members of the Cucurbitaceae family (pumpkin, watermelon, melon, cucumber) have tendrils.

Cladodium is a lateral shoot that has undergone modification, which is capable of continuous growth and has green, flattened long stems that take on the functions of leaves. Cladodium performs the function of photosynthesis, since well-developed chlorophyll-bearing cells are located under the epidermis. The group of plants with cladodes includes the Decembrist cactus, prickly pear, Mühlenbeckia planiflora, and southern carmichelia.

Phyllocladium is a modified flat leaf-shaped side shoot that has limited growth and serves as a leaf in the life of the plant. The lateral buds of the shoot give rise to phyllocladia, and therefore, phyllocladia are always located in the axils of small scale-like or membranous leaves. Such modified shoots perform the function of photosynthesis, so they look like leaves in appearance. Their growth is limited, and there is no metameric structure. Phyllocladies are characteristic of plants such as phyllanthus, mossy, butcher's broom, and some representatives of the Asparagus genus.

Modified underground shoots- these are the rhizome, caudex, bulb, corm, underground tuber and stolon. The conditions for the existence of shoots located underground are very different from the terrestrial environment. Therefore, they acquired other important functions, such as the ability to endure unfavorable periods of life, the deposition of nutrients into reserves, and the possibility of vegetative reproduction.

Rhizome (rhizome) is an underground shoot with scale-like leaves, adventitious roots and buds. Wheatgrass has thick and branched rhizomes. Kupena and iris have shortened and fleshy rhizomes, while water lilies and water lilies have the thickest rhizomes of all plants.

Caudex is a perennial structure derived from a shoot, characteristic of perennial grasses and subshrubs with a tap root system. The caudex, along with the root, is a place of accumulation of reserve nutrients and has many buds. Plants that have a caudex are lupins and alfalfas from the Legumes, femoris and ferula from the Apiaceae, dandelion, and wormwood from the Asteraceae.

Bulb is a specialized underground shortened shoot. In it, organic substances are stored in scales of leaf origin, the stem in the bulb is transformed into the bottom. Vegetative propagation is carried out using bulbs. Bulbs are formed in monocots of the Amaryllidaceae family (hyacinth, narcissus), the Liliaceae family (onion, tulip, lily), and less often in dicotyledonous plants.

Corm- also a modified underground shoot that has a thickened stem, where nutrients are stored, adventitious roots growing on the lower surface of the corm, and a protective cover of dried leaf bases. Corms are characteristic of saffron, gladiolus, ixia, and colchicum.

underground stolon is an annual long underground shoot. This thin shoot with underdeveloped scale-like leaves has a tuber or bulb at the thickened end with a reserve of organic substances. Underground stolons are formed in potatoes, adoxa, and sedmichnik.

underground tuber- a modified underground shoot, in which the storage function comes to the fore. This shoot has scale-like leaves that quickly fall off, and buds located in the axils of the leaves.

The shoot is one of the main vegetative organs of higher plants. It consists of a stem on which buds and leaves are located. The shoot is the most variable structural element of the plant in appearance.

The above-ground part of the plant is a shoot or shoot system.

The shoot consists of a stem (axis) and leaves and buds located on it. The place where a leaf is attached to the stem is called a node, and the area between two adjacent nodes is called an internode. The angle between the stem and the leaf is called the leaf axil. The shoot develops from the bud.

A bud is a rudimentary shoot with very shortened internodes. The central part of the bud is occupied by a rudimentary stem, at the top of which there is a growth cone, which is educational tissue. The stem contains rudimentary leaves. The outside of the bud is covered with bud scales, which can protect the rudimentary leaves and growth cone from unfavorable environmental conditions. To perform a protective function, the bud scales form thick pubescence, secrete resinous substances, etc. A modified shoot is a plant organ in which the shape and function of the stem, buds and leaves are irreversibly changed in the process of evolutionary adaptations to certain conditions of existence of the organism. In cultivated plants, shoot modification is caused by human intervention.

Metamorphoses of the shoot can be either minor or significant - up to greatly changed plant forms. Both main and lateral shoots, as well as buds and leaves, undergo metamorphosis.

The main types of shoots of green plants are aboveground and underground. Aboveground (aerial) shoots are assimilative, along the axis of which the leaves are located. Assimilating shoots are very diverse in appearance. In many cases, in addition to the main function of photosynthesis, such shoots perform the role of a storage and supporting organ of the plant, as well as the function of vegetative propagation.

Shoot modifications
Name	Functions	Plant
Rhizome (formed underground or when a shoot is drawn into the soil)	Supply of substances, reproduction, settlement	Sow thistle, anemone, lumbago, marigold,
Caudex (a thickened main shoot that turns into a taproot. As the plant ages, it dies, starting from the center.)	Stock of substances	Swimwort, asparagus, lungwort, crow's eye, mynika, wheatgrass, hoofed grass, amazing violet, strawberry, cuff, iris, lingonberry, gravilat, onion, blueberry, lily of the valley
Whiskers (thin shoots with scale-like leaves and rosettes in the internodes)
Tuber (formed at the ends of underground shoots-stolons)	Reproduction and dispersal	Strawberries, cinquefoil, gooseberry, sedmichnik, stone fruit
Corm	Substance storage and reproduction	Gladiolus, corydalis
Bulb	Substance storage and reproduction	Onion, lily, tulip, daffodil, hazel grouse
Succulent shoots	Water supply	Cacti, spurge
Spines (located in the axils of the leaves, and when they fall, above the leaf scar)		Hawthorn, apple tree
Phyllocladia (leaf-like shoots)	Photosynthesis	Asparagus, butcher's broom
Cladodia (flat photosynthetic shoots)	Photosynthesis	Phyllocactus, horsetails, zygocactus, horsetails
	Support attachment	Pumpkin, cucumber, hops

Modifications of aboveground shoots

Modified shoots are those that perform some additional functions: protection, climbing, storing nutrients, etc. Modified shoots include spines, tendrils, tubers, succulent shoots, stolons, and shoots of insectivorous plants. Spines are needle-like structures that protect the plant from being eaten by animals. Spines can be formed from leaves (barberry), stipules (yellow acacia), shoots (sea buckthorn, hawthorn). Tendrils are thread-like axillary shoots (grapes, cucumbers) that perform a supporting function. In peas, part of the leaf turns into tendrils. A tuber is a thickened shoot that serves as a reserve of nutrients (kohlrabi cabbage - approx. biofile.ru). Stolons (common name “mustache”) are horizontal creeping shoots that promote plant reproduction. On each stolon there are rosettes with adventitious roots. After the rosette takes root, the horizontal shoot dies (strawberry, creeping tenacious).

Succulent shoots are an adaptation of plants to hot and dry climates. Their function is to store moisture. Water can accumulate in the leaves (sedum, sedum, aloe) or in the stem (euphorbia, cactus). Mexican cacti have fleshy stems of a wide variety of shapes: ribbed balls, columns, cylinders, even candelabra and cakes. Cacti have no green leaves: they have turned into bunches of thorns. The function of photosynthesis is performed by the stems.

Underground modified shoots.

Stolons and tubers can be either aboveground or underground. In addition to them, underground shoots include rhizomes and bulbs. Underground stolons perform the same functions as aboveground stolons - plant dispersal and reproduction. This explains the similarity in their structure. Tuber. This shoot has a short and thick stem. The scaly leaves quickly die off and scars remain in their place (in potatoes they are popularly called “edges”). In their sinuses there are buds called “eyes”. The tuber performs the function of storing nutrients (for example, starch), surviving unfavorable seasons and reproduction. Not only potatoes have tubers, but also Jerusalem artichoke and corydalis. They appear on underground stolons. The rhizome often looks like a root in appearance, but the rhizome also has scaly leaves, and in their axils there are lateral buds, and at the top there are apical buds. Adventitious roots are formed on the rhizome. Unlike the stolon, the rhizome is a perennial shoot that allows the plant to survive unfavorable conditions. This underground shoot is common to many plants and can perform a variety of functions. Nutrients are stored in the thick short rhizomes of iris, kupena. Creeping wheatgrass, mouse pea, and lily of the valley have long and thin rhizomes. They are able not only to store nutrients, but also to capture new territories. The rhizome not only grows quickly in length (for butterbur the life span is 1.5 meters, for coltsfoot - a meter - approx. biofile.ru), but it also branches. As a result, the mother plant may split into several daughter plants. Rural residents know how difficult it is to fight long-rhizome weeds: wheatgrass, cowgrass, coltsfoot. Sea buckthorn, rose hips, and raspberries grow quickly. The bulb is a greatly shortened, modified shoot with a flat stem – “bottom”, with leaves in the form of scales. The scales can be succulent (storing) or dry covering), can be narrow and only slightly cover each other (lily) or embrace each other almost completely (hyacinth, tulip, onion). The bulb allows the plant to survive unfavorable periods of the year. Axillary buds can turn into bulbs - babies. Consequently, the bulb is also a propagation shoot. In the colchicum and gladiolus, the underground shoot is called a corm. Externally, the corm resembles an onion, but differs from it in its highly overgrown bottom, to which small scale-like leaves are attached, and serves as an organ for storing reserve nutrients. The corm has well-developed apical and axillary buds, giving rise to flowering shoots and daughter corms.

VEGETATIVE REPRODUCTION, the formation of a new organism from a part of the mother; one of the ways of asexual reproduction of multicellular organisms. In lower plants (for example, in algae) it is often carried out by division, in fungi - by budding (for example, in yeast, some basidiomycetes) or parts of the mycelium (for example, in cap mushrooms), in higher plants - by parts of vegetative organs ( root, stem, leaf), but more often in their modified forms - rhizomes (wheatgrass, pigweed, etc.), tubers (potatoes, dahlias, etc.), bulbs (onion, tulip, etc.), root suckers (raspberries, cherries, plum, etc.), tendrils (strawberries, wild strawberries), etc. Characteristic of almost all perennial plants (based on their ability to regenerate). The vegetative offspring of one individual is called a clone. Artificial methods of vegetative propagation include all natural ones, as well as reproduction cuttings(currant, sea buckthorn, grapes, aloe, begonias, etc.), vaccination cuttings and bud (pear, apple, rose, lilac, etc.), layering(currants, hazelnuts, etc.). Vegetative propagation of cultivated plants has been used for many centuries. Modern practice uses effective tissue culture methods (micropropagation). Clonal micropropagation is based on obtaining planting material from cells of the apical meristem (shoot tips). This method makes it possible to obtain from one plant within a year, by the required date, several thousand plants that have maternal characteristics and are free from viral and other infections. In this way, planting material for vegetable, fruit and ornamental plants is obtained. In animals, vegetative reproduction is carried out either by fragmentation - separation of body parts from the mother's body, which then complete themselves into a whole organism, or by budding. During budding, an outgrowth (bud) is formed on the mother’s body, from which a new individual develops. Vegetative reproduction is characteristic of some worms, sponges, coelenterates, and tunicates.