The rhizome is a modified shoot and the tuber is a modified stem. The structure of the onion bulb. What plants have rhizomes
Question 1. What modified underground shoots do you know? Name plants that have a rhizome, tuber, bulb.
Tubers are formed as terminal thickenings of underground shoots - stolons. Stolons grow from the base of above-ground stems. Tubers develop as a result of thickening of the apical buds of stolons (potato, Corydalis, pear). On them are groups of kidneys, which are called eyes. The tubers are used for vegetative propagation.
The bulb is an underground shortened modified shoot. The stem of the bulb forms the bottom. Leaves, or scales, are attached to the bottom. The outer scales are usually dry, they perform a protective function. They cover the juicy scales, in which nutrients and water are deposited. At the bottom there is an apical bud, from which aerial leaves and a flower-bearing arrow develop. Adventitious roots develop on the lower part of the donut. Bulbs are characteristic of perennial plants (lilies, tulips, onions, garlic, narcissus, wild onions, etc.). Bulbs allow plants to reproduce vegetatively.
The rhizome is also an underground shoot that looks like a root. The rhizome bears scale-like leaves, in the axils of which are axillary buds. Adventitious roots are formed on the rhizome, and lateral branches of the rhizome and above-ground shoots develop from the axillary buds. Rhizomes are found in perennial herbaceous plants (horsetails, ferns, nettles, lilies of the valley, cereals, etc.). The rhizome is an organ of vegetative reproduction.
Question 2. How to distinguish a rhizome from a root?
In appearance, the rhizome resembles a root, but differs from it in the presence of scaly leaves, leaf marks (scars from fallen leaves), buds, and the absence of a root cap.
Question 3. How does a potato tuber develop?
Organic matter constantly flows from potato leaves through the stems into underground shoots (stolons) and is deposited in the form of starch in the tops of stolons. The tops of stolons grow, thicken and turn into large tubers by autumn.
Question 4. Why should a potato tuber be considered an escape?
A potato tuber should be considered a shoot because, like a shoot, it is formed by a stem that performs a storage function, has buds (eyes) and scaly leaves.
Question 5. What is the structure of the bulb?
In the lower part of the bulb, for example, onions, there is an almost flat stem - the bottom. Adventitious roots and modified leaves (scales) depart from the bottom. Outer leaves - scales - dry and leathery, they perform a protective function; internal - fleshy and juicy, nutrients are deposited in them. In the axils of the scales there are axillary buds.
Question 6. How to prove that the rhizome and bulb are modified shoots?
Outwardly, the rhizome resembles a root, but, like a ground shoot, it has apical and axillary buds, as well as membranous scales - modified leaves. Thus, the rhizome has a stem (the axial part of the rhizome, buds and leaves (membraneous scales), that is, what is characteristic of the shoot. At the bulb, we can also see all parts of the shoot: the stem (bottom of the bulb), leaves (dry and juicy scales) and buds (between scales) This confirms that the rhizome and bulb are modified shoots.
Question 7. What above-ground modifications of shoots do you know?
Terrestrial modifications of the shoot include thorns (wild apple tree, wild pear), antennae (pumpkin, grapes), lashes (bone, tenacious), above-ground stolons, or mustaches - (strawberries), cactus stems.
A tuber is a part of a plant that is its modified organ. It is necessary for the body to perform additional functions. Features of its structure and varieties of tubers of various origins will be discussed in detail in this article.
The purpose of the modifications
The underground and aboveground organs of plants are, respectively, the root and the 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 process of adaptation and increase in viability. For these purposes, modifications are needed. The tuber is a prime example of one of them.
A good example of the modification of the underground organ of plants are root crops. 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
The tuber and rhizome are modifications of above-ground organs. There is nothing surprising in this. Despite the location underground, in their structure they have all the parts of the escape. Their examples are tubers, bulbs, rhizomes, tendrils and whiskers. Each of them has its own structural features that determine their functions. For example, the whiskers of strawberries are necessary for vegetative propagation. Although they form flowers and seeds, this method is the most essential. But the mustache of grapes is needed to attach its lashes to the support.
The bulb of a leek or garlic consists of a flat stem, which is called the bottom. Attached to it They grow in a bunch. This is a typical structure for the bottom also contains 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 against mechanical damage and excessive transpiration. From the buds located on the bottom, young green leaves periodically grow. They are called green onions. All of the above structural features prove once again that the bulb is a modification of the shoot.
The structure of the tuber
The next example of the modification of above-ground organs is the tuber. It is typical for potatoes, Jerusalem artichoke, kohlrabi. The tuber is the result of thickening of the internodes of the stem, which can be both underground and aboveground.
Its basis is a thickened stem, rich in starch and other substances. The bark protects it from adverse environmental conditions. This is what we peel off when we use potatoes for cooking. There are also buds on the thickened stem. They are called eyes. With their help this plant is carried out. In the spring, young shoots appear from the buds, which form a bush and new tubers.
root tuber
Not only shoots are able to form tubers. The underground part of the plant is also no exception. So, the root tuber is characteristic of dahlia, sweet potato and chistyak. It is nothing more than a thickening of the adnexal components. Despite the different origin and location, 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 basic tissue, that plastids, leukoplasts, containing carbohydrates are located. In this form, plants with these changes easily endure adverse conditions, surviving them underground.
Another important function of this modification is the implementation of vegetative reproduction. To grow potatoes, it is enough to cut the tuber into several parts, each of which must have buds - eyes, and plant them in the ground. This plant has fruits capable of producing seeds. But their number is small. Since potatoes are of great economic importance, breeders have attempted to develop new varieties with a large number of seeds. But the vegetative method of reproduction with the help of tubers turned out to be more productive.
Since the tuber is a storehouse of nutrients, such modified elements are used as food. And Jerusalem artichoke is able to lower the level of glucose in the blood with constant use. Doctors recommend it to people suffering from diabetes. The use of potatoes provides the body not only with the necessary daily carbohydrate content, but also with valuable trace elements, such as phosphorus and potassium.
Thus, tubers are modifications of a shoot or root and serve to store nutrients, vegetative propagation. They are of great food and economic importance.
Modified shoots, in comparison with traditional above-ground organs of plants, are able to perform additional functions. What structural features make this possible?
Features of the structure of the shoot
The shoot is the above ground part of the plant. Its base is the stem. This is the axial part of the shoot, on which the leaves and buds are located. Depending on the location in space, erect, creeping, curly, creeping, clinging shoots are distinguished.
The places where the leaves attach to the stem are called nodes, and the distance between them is called an internode. On the shoot are also rudimentary organs called kidneys. If leaves develop from them, they are vegetative, and if flowers are generative.
Escape functions
The aboveground organ of plants performs the function of vegetative propagation. During this process, a multicellular part is split off from the whole organism, due to which its integrity is restored.
The shoot plays an important role in the implementation of growth and regeneration. Due to the presence of chloroplasts in the cells of 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, typical structural features are not enough. Therefore, modified shoots are often found in nature. Due to the formation of various thickenings and changes in shape, they can store water and nutrients, ensure the viability of plants in 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. Above-ground modifications of the shoot are mustaches, antennae, spines. Let's consider their structure in more detail.
Bulb
Well-known onions and garlic are also an underground modification of the shoot. At its base is a flat stem, which is called the bottom. Vegetative buds develop on it, from which leaves are formed. They are of three types:
- membranous;
- juicy;
- young.
Leaves of the first type will perform the main function of the bulb. They store water with mineral solutions. Dry membranous leaves are a protection against mechanical damage and adverse conditions. Young leaves grow from the vegetative buds of the donets, which are often called green onions.
Bulbous plants underground tolerate drought and frost. So, for example, tulips, crocuses, lilies grow and fade during the wet and warm season, after which young bulbs form underground. They are usually dug up after flowering, stored in a cool place, and seated at the end of summer.
Why is a tuber a modified shoot?
Many modified shoots grow underground. For example, potato or Jerusalem artichoke tubers. Therefore, they are often confused with another vegetative organ of plants - the root. It is very easy to prove that a tuber is a modified shoot. Its thickened part is the stem. It accumulates the reserve carbohydrate of plants starch. The covering tissue of this shoot is the bark. We cut it when we "peel potatoes". Another proof is the presence of kidneys. They are called eyes. In the spring, young shoots develop from them.
Rhizome
The rhizome is a modified shoot, which is also located underground. Despite the name, it has nothing to do with the underground plant organ. The rhizome consists of elongated internodes, on which vegetative buds develop. Leaves develop from them in spring. Soil nutrition is carried out by a fibrous root system, which grows in bunches.
If you've ever tried to get rid of the nasty wheatgrass weed, you know that it can be quite difficult to do so. 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 a rhizome is typical for lily of the valley, kupena, mint, irises, asparagus.
Mustache and moustache
And these above-ground modified shoots are often confused with each other because of similar names. In fact, they have different origins, and therefore functions. Mustaches, or stolons, are found in strawberries, strawberries, chlorophytum, saxifrage. Most often, these are creeping shoots with elongated internodes and a system of adventitious roots. They develop simple leaves. These structures are able to take root and give rise to a new organism. This is how they reproduce sexually.
Antennae are formed in grapes, ranks, peas, beans. They can develop from a stem or leaves. They help climbing plants hold onto a support. As it grows, the antennae, like a spiral, twist around various objects. As a rule, if such structures do not come into contact with the support, they dry out and die.
Claudius
Almost every lover of indoor flowers has a zygocactus ("Decembrist") growing in their house. His escape is called the cladode. This modification is a flattened stem that acts as a leaf. This is manifested in the fact that the cladodium carries out photosynthesis. Stem origin proves the formation of flowers on it, which never form on leaves. The same modified shoots are found in prickly pear, asparagus, and smilax.
The meaning of escape modifications
Metamorphoses of vegetative organs significantly increase the adaptive capacity of plants. Modified shoots perform additional functions in the plant body in the form of maintaining a reserve of substances and providing an additional method of vegetative reproduction.
Thanks to them, a person receives a large amount of planting material. We eat potato tubers, leeks 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 bulbs, tubers, mustaches, tendrils and rhizomes.
652-01. The similarity of a potato tuber with a linden shoot is that the tuber has
A) kidneys
B) stock of starch
B) leaves
D) flowers
Answer
652-02. The bulb is a modified shoot, this proves the presence of
A) main root
B) buds-eyes
B) underground stolons
D) flat stem - bottom
Answer
652-03. Rhizome - a modified shoot, this proves the presence on the rhizome
A) main root
B) membranous scales
B) flat stem - bottom
D) mechanical fibers
Answer
652-04. Modified shoots include the edible part
A) carrots
B) potatoes
B) beets
D) turnips
Answer
652-05. The similarity of a potato tuber with a poplar shoot lies in the presence
A) kidneys
B) stock of starch
B) leaves
D) peephole
Answer
652-06. The rhizome is a modified
A) escape
B) tuber
B) main root
D) adventitious root
Answer
652-07. The tuber is a modified shoot, this proves the presence on the tuber
A) membranous scales
B) buds-eyes
C) fleshy and juicy scales
D) flat stem - bottom
Answer
652-08. What is a potato tuber?
A) underground escape
B) modified stem
B) rhizome
D) root crop
Answer
652-09. Are the following statements about modified plant organs correct?
1. Rhizome is an organ of mineral nutrition of plants.
2. In the lower part of the onion bulb there is a flat stem - the bottom, modified leaves develop on it.
A) only 1 is correct
B) only 2 is true
C) both statements are correct
D) both statements are wrong
Answer
652-10. Which of the modified organs is a modified shoot?
Answer
652-11. The bulb is a modified shoot found in
A) lilies
B) potatoes
B) wheatgrass
D) fern
Answer
652-12. An underground shoot can be distinguished from modified roots by the presence of
A) kidneys
B) root hairs
C) lateral and adventitious roots
D) storage tissue
Answer
652-13. Which plant reproduces with a bulb?
A) tulip
B) potatoes
B) carrots
D) strawberry
Answer
652-14. Which of the modified organs is a modified shoot?
Answer
652-15. Are the following statements about modified plant organs correct?
1. The inner fleshy and juicy leaves of the onion bulb contain water and nutrient reserves.
2. On the rhizomes of plants there are membranous scales - modified leaves.
A) only 1 is correct
B) only 2 is true
C) both statements are correct
D) both statements are wrong
Answer
652-16. They differ in structure, but are modifications of the same plant organ.
A) poppy leaf and dandelion stem
B) rye root and corn shoot
C) potato tuber and dahlia fruit
D) tulip bulb and lily of the valley rhizome
Answer
652-17. As a result of thickening of the lateral and adventitious roots,
A) aerial roots
B) root tubers
B) roots
D) sucker roots
Modifications are associated with the performance of special functions by them (these are sharp, hereditarily fixed changes). The most common modified shoots are rhizomes, tubers, bulbs growing in the ground. They deposit reserve nutrients necessary to endure adverse conditions and serve for natural vegetative reproduction.
Rhizome
occupy a horizontal position in the soil. It usually has scaly leaves and buds. Adventitious roots depart from it. Spare 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 has reduced leaves in the form of brown or colorless scales, and in their axils there are buds from which aerial shoots grow. They have nodes and internodes, adventitious roots are formed from the nodes. At the top is the apical bud, due to which the rhizome grows in length. Plants with branching rhizomes grow rapidly (couch grass, lily of the valley, iris, kupena, etc.). The life span of rhizomes ranges from 2-3 to several decades. Thin, elongated underground shoots bearing a tuber or bulb at the top, called stolons.Tuber
- this is a shoot with a strongly thickened stem, in which reserve nutrients are deposited. Tubers can be underground and aboveground: Underground - develop on stolons (potato, pear). Elevated - develop in kohlrabi cabbage, some orchids. On the tuber there are eyes - recesses in which the kidneys are located. They are located on the tuber in a spiral (like leaves on the stem) and give rise to above-ground shoots. Outside, the tuber is covered with epidermis, which is subsequently replaced by cork. In potatoes, tuber pulp cells are filled with starch, and ground pear - inulin (a complex carbohydrate). Tubers develop from the apical buds of stolons.Bulb
- an underground shoot with a shortened stalk bottom. Adventitious roots extend downward from the bottom, and closely adjacent succulent leaves (bulbous scales) in which reserve nutrients are deposited upward. 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, giving rise to an above-ground shoot - a flower-bearing "arrow" and leaves. Bulbs help the plant survive in adverse conditions and are the organ of vegetative reproduction.Conclusion:
1. Tuber, bulb, rhizome are modified shoots, because they have buds, shortened internodes, a large supply of organic matter, no chlorophyll; with their structure, they repeat the structure of above-ground shoots.Modified shoots are a kind of pantry, where nutrients containing starch, sugars, minerals, phytoncides (substances that kill microbes) accumulate. They are widely used for human food and used for animal feed. In addition, they also have great biological significance - all are organs of natural vegetative reproduction that occurs in nature without human intervention.