The structure of tissues of potatoes, vegetables, fruits. Practical work "Cooking and examining the pulp of a tomato fruit with a magnifying glass

The tissue (pulp) of potatoes, vegetables and fruits consists of thin-walled cells that grow approximately equally in all directions. This tissue is called parenchyma. The contents of individual cells is a semi-liquid mass - the cytoplasm, into which various cellular elements (organelles) are immersed - vacuoles, plastids, nuclei, starch grains, etc. (Fig. 9.2). All cell organelles are surrounded by membranes. Each cell is covered with a shell, which is the primary cell wall.

The shells of each two neighboring cells are fastened with the help of the middle plates, forming the backbone of the parenchymal tissue (Fig. 9.3).

Contact between the contents of the cells is carried out through plasmodesmata, which are thin cytoplasmic strands passing through the membranes.

The surface of individual specimens of vegetables and fruits is covered with an integumentary tissue - epidermis (fruits, ground vegetables) or periderm (potatoes, beets, turnips, etc.).

Because in fresh vegetables contains a significant amount of water, then all the structural elements of their parenchymal tissue are hydrated to one degree or another. Water as a solvent has an important effect on the mechanical properties of plant tissue. By hydrating to some extent hydrophilic compounds, it plasticizes the structure of the walls and middle plates. This provides a sufficiently high turgor pressure in the tissues.

Turgor is a state of tension arising from the pressure of the contents of the cells on their elastic membranes and the pressure of the membranes on the contents of the cells.

Turgor pressure can decrease, for example, when vegetables and fruits wither or dry out, or increase, which is observed when wilted vegetables are immersed in water. This property of vegetables and fruits can be taken into account in their culinary processing. So, potatoes and root crops with a weakened turgor are recommended to be soaked for several hours before mechanical cleaning to reduce processing time and reduce the amount of waste.

Rice. 9.2. The structure of a plant cell

Rice. 9.3. Plant tissue wall:

1 -- middle plate; 2 - plasmalemma.

Magnification x 45000 (according to J.-C. Roland, A. Seleshi, D. Seleshi)

The vacuole is the largest element located in the center of the cell. It is a kind of bubble filled with cell sap, and is the most hydrated element of the vegetable and fruit parenchyma cell (95 ... 98% water). The composition of the dry residue of cell sap includes, in one amount or another, almost all water-soluble nutrients.

The main mass of sugars contained in potatoes, vegetables and fruits in a free state, soluble pectin, organic acids, water-soluble vitamins and polyphenolic compounds is concentrated in vacuoles.

The cell sap contains approximately 60 ... 80% of minerals from their total amount in vegetables and fruits. Salts of monovalent metals (potassium, sodium, etc.) are almost completely concentrated in the cell sap. Salts of calcium, iron, copper, magnesium are contained in it somewhat less, since they are part of other tissue elements.

Cell sap contains both free amino acids and soluble proteins, which form solutions of relatively low concentration in vacuoles.

A thin layer of cytoplasm with other organelles occupies a near-wall position in the cell. The cytoplasm consists mainly of proteins, enzymes and a small amount of lipids (the ratio of proteins and lipids is 90:1). In the cytoplasm, as in vacuoles, they are in the form of a solution, but more concentrated (10%).

Plastids are organelles that are present only in plant cells. The most typical of these are chloroplasts, which contain chlorophyll. Under certain physiological conditions, plastids do not form chlorophyll; in these cases, they produce either proteins (proteoplasts) or lipids and pigments (chromoplasts), but most often such plastids perform reserve functions, and then starch (amyloplasts) accumulates in them, so plastids are colored and colorless. The latter are called leukoplasts.

The composition of chloroplasts, in addition to chlorophyll, includes proteins and lipids in a ratio of 40:30, as well as starch grains.

During the development of chromoplasts, large globules or crystals containing carotenoids, including carotenes, are formed. The presence of these pigments in green vegetables and some fruits (gooseberries, grapes, renklod plums, etc.) causes different shades of their green-yellow color. Carotenes give a yellow-orange color to carrots, turnips, etc. However, orange color does not always indicate their high content in fruits and vegetables; for example, the color of oranges, tangerines is due to another pigment - cryptoxanthin. At the same time, the relatively high content of carotene in green vegetables can be masked by chlorophyll.

Amyloplasts are filled mainly with large starch granules. It should be noted that in plant cells, all the starch grains contained in them are located in a space limited by the shell of amyloplasts or other plastids.

The cell nucleus contains chromatin (despiralized chromosomes), consisting of DNA and basic proteins (histones), and nucleoli rich in RNA.

Membranes are an active molecular complex capable of exchanging substances and energy.

The cytoplasm at the border with the cell wall is covered with a simple membrane called the plasmalemma. The outer edge of the plasmalemma can be seen when examining plant tissue preparations treated with a concentrated saline solution under a microscope. Due to the difference between the osmotic pressure inside the cell and outside it, water passes from the cell into the environment, causing plasmolysis - the separation of the cytoplasm from the cell membrane. Similarly, plasmolysis can be induced by treating sections of plant tissue with concentrated solutions of sugars or acids.

Cytoplasmic membranes regulate cell permeability by selectively retaining or passing molecules and ions of certain substances into and out of the cell.

The vacuole, like the cytoplasm, is also surrounded by a simple membrane called the tonoplast.

The main structural components of membranes are proteins and polar lipids (phospholipids). Exist Various types structures of the cytoplasmic membrane: three-layer (from two layers of protein with a biomolecular layer of lipids), granular (from particles whose diameter is about 100 10-10 m, or from smaller particles - subunits). At present, the membrane is considered as a liquid structure penetrated by proteins.

The surface of nuclei, plastids and other cytoplasmic structures is covered with a double membrane consisting of two rows of simple membranes separated by a perinuclear space. These membranes also prevent mixing of the contents of two adjacent organelles. Individual substances pass from one organelle to another only in strictly defined quantities necessary for the flow of physiological processes in tissues.

Cell walls in combination with the middle plates are called cell walls. Unlike membranes, they are characterized by complete permeability.

Cell walls make up 0.7 ... 5.0% of the fresh weight of vegetables and fruits. So, in vegetables of the fruit group, for example, in zucchini, their number does not exceed 0.7%. AT leafy vegetables - white cabbage, lettuce, spinach - about 2%. Root crops differ in the highest content of cell walls - 2 ... 4%.

The composition of the cell walls mainly includes polysaccharides (80 ... 95%) - cellulose, hemicelluloses and protopectin, therefore they are often called cell wall carbohydrates. The composition of the cell membranes includes all of the above polysaccharides. It is believed that the middle plates consist mainly of acidic polysaccharides (protopectin), which play the role of an intercellular cementing substance, which is sometimes accompanied by protein compounds, and in the oldest tissues - lignin.

Tab.9.1. The content of extensin and hydroxyproline

in the cell walls of some plant foods(%)

In addition to carbohydrates, the cell walls contain nitrogenous substances, lignin, lipids, waxes, and minerals.

Of the nitrogenous substances in the cell walls of plant tissue, a structural protein of extension was found - a polymer from the group of glycoproteins, the protein part of which is associated with carbohydrates - the residues of arabinose and galactose. The molecular weight of the protein part of such macromolecules is 50,000, the extension has the form of a rigid rod, 50% consists of hydroxyproline. The cell wall contains several protein fractions that differ in the content of hydroxyproline.

Extensions in some respects resemble the protein collagen, which performs similar functions in animal tissues. The content of extensin and hydroxyproline in the cell walls of various vegetables and potatoes is not the same (Table 9.1). The cell walls of a potato consist of about 1/5 of extensin. In the cell walls of root crops, it is contained 2 times less than in the cell walls of potatoes; in the cell walls of melon, the content of extensin does not exceed 5%.

The ratio of carbohydrates and extensin in cell walls depends on the type of plant tissue. The cell walls of many plant foods are about 1/3 cellulose, 1/3 hemicellulose, and 1/3 pectin and protein. In the cell walls of tomatoes, there is another 1:1 ratio between carbohydrates and protein.

Lignin is a complex natural polymer that forms the cell walls of plants. It plays the role of an encrusting substance that holds together cellulose and hemicellulose fibers. It is covalently bound to hemicellulose polysaccharides (xplan), pectins and protein. The content of lignin in plant tissues depends on their type and degree of lignification. A significant amount of lignin is contained in the cell walls of beets, carrots, less accumulates in white cabbage.

Due to the fact that the softening of potatoes, vegetables and fruits, which occurs during their thermal cooking, is associated with the destruction of cell walls, it seems appropriate to consider the structure of the latter.

According to modern concepts, the cell wall is a highly specialized aggregate consisting of various polymers (cellulose, hemicellulose, pectin, proteins, etc.), the structure of which in different plants is encoded with the same degree of accuracy as the structure of protein molecules.

On fig. 9.4 shows a model of the structure of the primary cell wall.

The primary cell wall consists of fibers (microfibrils) of cellulose, which occupy less than 20% of the volume of the hydrated wall. Being parallel in the cell walls, cellulose fibers form micelles with the help of hydrogen bonds, which have a regular, almost crystalline packing. One micelle of cellulose can be separated from another by a distance equal to ten of its diameters. The space between cellulose micelles is filled with an amorphous basic substance (matrix) consisting of pectin substances, hemicelluloses (xyloglucan and arbinogalantan) and a structural protein associated with tetrasaccharides.

The primary cell wall is considered as a whole bag-like macromolecule, the components of which are closely interconnected. Numerous hydrogen bonds exist between cellulose micelles and xyloglucan. In turn, xyloglucan is covalently linked to the galactan side chains of pectin substances, and pectin substances through arabinogalactan are covalently linked to the structural protein.

Considering that the cell walls of many vegetables and fruits are characterized by a relatively high content of divalent cations, mainly Ca and Mg (0.5 ... 1.0%), chelate bonds in the form of salt bridges.

Rice. 9.4. The structure of the primary cell wall (according to Albersheim):

1 - cellulose microfibril: 2 - xyloglucan; 3 - main

rhamnogalacturonic chains of pectin substances; 4 - side

galactan chains of pectin substances; 5-structural protein

with arabinose tetrasaccharides; 6- arabinogalactan

The probability of formation of salt bridges and the degree of esterification of polygalacturonic acids are inversely related. Salt bridges contribute to the strengthening of cell walls and parenchymal tissue in general.

The integumentary tissues of potato tubers, root crops and other vegetables are characterized by a reduced nutritional value due to the concentration of fiber and hemicelluloses in them, therefore, during the cooking of potatoes and most vegetables, these tissues are removed.

Tubers differ from rhizomes in that their stem is short and thick, and the leaves are underdeveloped. As with any shoot, they have buds and are located at the top and in the axils of underdeveloped leaves. Adventitious roots do not develop on tubers. Potato tubers do not grow immediately from underground buds. First, a long white underground shoot grows from the kidney - a stolon. Stolon lives less than a year. The top begins to thicken over time and turns into a tuber by autumn.

A lot of starch accumulates in the tuber in the form of small grains. A potato tuber is a modified shoot with a thickened stem and small leaves.

What to do. Consider the external structure of a potato tuber.

What to watch. Find on its surface the apical and axillary buds (eyes), scars from leaves (brows) and a scar from a separated stolon.

What to do. Count the number of eyes on the tuber.

What to watch. Locate the top and bottom of the tuber.

Note the uneven distribution of eyes on the thickened stem.

That part of the tuber, where there are more eyes, is called the top, and the opposite, where the scar from the stolon is called the base.

What to do. Cut the tuber into two pieces. Drop a drop of iodine solution on the cut of the tuber.

• How did the color of the tuber section change?
• What substances are deposited in the tuber cells?
• What is the importance of a tuber in the life of a plant?

Prepare for a report. Draw in a notebook appearance tuber and label its parts. Write down the signs that prove that the tuber is a shoot.

The BBC Future columnist decided to find out more about the most popular root vegetable in many countries and about the properties that make one or another variety of it optimal for cooking some dishes and completely unsuitable for others ... Boiled, baked, fried or mashed - no matter how you cook potatoes, spoil it is, generally speaking, difficult.

There is something in the satiety of well-baked potatoes, in the crunch of potato chips, in the creamy tenderness of mashed potatoes, something that resonates with warmth not only in our taste buds, but also in the heart.

(According to the best mashed potatoes recipe I know, by the way, pre-melted butter should be added to boiled potatoes gradually and until it stops being absorbed.)
This is such a familiar food product for us that when preparing it, we often do not take into account the difference even between species that look different from each other.

Meanwhile, not every potato is suitable for frying in a deep fryer, and only certain varieties are good in a salad. At school lessons in home economics, they usually do not teach to distinguish potatoes by variety, and it all seems to us “on the same face”.
However, anyone who has tried the same variety both fried and boiled for salad knows perfectly well that there is no equality in the world of root vegetables either.
Varieties differ in their chemical composition and, accordingly, technological properties. So if you want to succeed in a potato dish, it is very important to choose tubers with the right characteristics.

To the deep fryer, for example, some types should not be allowed in any way. I recently witnessed this personally in my kitchen, and the alarm signals from the smoke detector dispelled my last doubts about the professional suitability of the kind of potato from which I tried in vain to make chips.

There are hundreds of different varieties of potatoes, and, according to nutritionists and breeders, tubers with a yellowish, brown, purple or red skin can be quite different from each other not only in appearance, but also in their chemical composition.
The main difference is in the percentage of starch, and according to this criterion, potatoes are divided into two main categories.

The first type - starchy (or mealy) - includes potatoes with a high content of starch (an average of about 22% of the mass of the tuber, according to the results of a study by Diana McComber, which is cited in her work by nutritionist Guy Crosby).
It is dry and flaky; upon heat treatment, it acquires a granular texture.

Craving crispy fried potatoes? Then try not to use the so-called waxy potato - with it you will not get the desired result. The exemplary representative of the starchy potato (at least in the USA) is the Russet variety, which has a reddish skin. It is ideal for frying. Its low water content means that when the chips come into contact with boiling oil, most of the water boils away before a crust forms on the surface, leaving just enough moisture left to steam the insides of each piece.

The numerous starch molecules in the Russet potato help to brown the edges of the cut slices, and because the flesh is quite dense, the chips are not in danger of being undercooked due to the oil that has penetrated deep inside.
Starchy potatoes are also suitable for mashing and baking.
Comparing the two types of cooked potatoes under a microscope, the researchers found interesting differences.
But woe to the cook who boils potatoes with a high starch content for salad - having absorbed water, it will quickly fall apart.

In a salad, it is better to put potatoes of wax varieties, which have a thin skin and watery pulp. It contains only about 16% starch, and when cooked, the tubers retain the integrity of the tissue.
Many of the varieties belonging to this category, by the way, have beautiful names, often formed from female names: "Charlotte", "Anya", "Kara" ...
Comparing the past under a microscope heat treatment starchy and waxy potatoes, the researchers found interesting differences between the two.
Unlike wax varieties, floury starch molecules tend to suck moisture from neighboring tissue areas.
That is why starchy varieties are perceived by us as dry and crumbly, and we recognize waxy ones by their wateriness.
Under a microscope, you can see that the cells that make up the tissue of starchy potatoes break up into small groups, like crumbs, when cooked. shortbread biscuits, and the tuber loses its structural unity. Waxy potatoes, on the contrary, keep their shape perfectly. This is explained by the fact that in boiled mealy potatoes, the breakdown of starch grains contained in the cells begins at lower temperatures than in wax potatoes (the difference is almost 12C).

As a result, in the first type, intercellular bonds are weakened faster, and the cell walls are destroyed by more early stages thermal cooking process.
Not every type of potato is also suitable for beloved by many mashed potatoes.
These properties of potatoes are important to consider when choosing a variety that matches a particular culinary task. However, this knowledge may be needed not only at home in the kitchen.

Raymond Wheeler's article, Potatoes for Human Life Support in Space, talks about experiments to grow potatoes in zero gravity.

For manned interplanetary flights, the ability to grow edible fruits will be key, and for decades, experiments have been conducted to find out how potatoes and other crops behave in growth chambers under different external conditions. Varieties that are classified as starchy types are being tested , and to wax, and, apparently, chefs will not be able to get rid of the problem of choice even in space.

However, those astrochefs who fly to Jupiter will be rewarded - according to some scientists, chips cooked in the gravity of this planet have the perfect crunchiness.
But we have other laws of attraction on Earth. And then the Chinese government unexpectedly announced that the potato will now become a staple in the Chinese diet, along with rice and wheat.
Until now, potatoes in China have been used mainly as a seasoning for rice, and not as a full-fledged side dish.

In Chinese cuisine, finely chopped tubers are usually marinated in vinegar and then fried with hot pepper Chile. Another popular cooking method is to stew with the addition of soy sauce and anise.
However, the promised status of the main product does not mean at all that with its acquisition, the potato will take a more prominent position on the Chinese table. It is unlikely that baked "Russet" will replace traditional rice.
According to whatsonweibo.com observers, which covers the main trends of Chinese media, including social media, China’s culinary life will most likely include not whole potato dishes, but potato flour products, such as noodles and buns.

If so, then Chinese consumers will not have to rack their brains over choosing the right variety of potatoes, the choice will be made for them by the manufacturer.

»: Enhanced Level white blood cells, a bacterial infection, potatoes contain starch, insects carry diseases - these and other similar statements can be heard from everywhere. Every day, from TV screens, from the lips of acquaintances, from the pages of newspapers and magazines, the same information enters our brain. Information that, as it may seem, is the lot of only specialists - physicians and biologists. After all, it is they who deal with these issues in their Everyday life. A simple person gets only conclusions from certain studies, dry words that do not have visibility. In this article I will try to tell simply about the complex. About how everyone can bring the seemingly elusive world of cells and microorganisms closer to them.

It's been two years now that I've been watching this world at home, and a year since I've been taking photographs. During this time, I managed to see with my own eyes what blood cells are, what falls from the wings of butterflies and moths, how the heart of a snail beats. Of course, much could be learned from textbooks, video lectures, and thematic websites. The only thing that would not be gleaned is the feeling of presence and proximity to something that is not visible to the naked eye. What is read in a book or seen on a TV show is likely to be erased from memory in a very short time. What is seen personally through the lens of a microscope will remain with you forever. And it will remain not so much the image of what he saw, but the understanding that the world is arranged in this way, and not otherwise. That these are not just words from a book, but personal experience. An experience that is now available to everyone.

What to buy?

Theater begins with a hanger, and research begins with the purchase of equipment. In our case, it will be a microscope, because you can’t see much through a magnifying glass. Of the main characteristics of the microscope "for home use", it is worth highlighting, of course, the set of available magnifications, which are determined by the product of the magnifications of the eyepiece and the objective. Not every biological sample is good for research at high magnifications. This is due to the fact that a larger magnification of the optical system implies a smaller depth of field. Consequently, the image of uneven surfaces of the drug will be partially blurred. Therefore it is important to have a set lenses and eyepieces, which allows observing in the entire magnification range: 10–20×, 40–60×, 100–200×, 400–600×, 900–1000×. Sometimes a 1500x magnification is justified, which is achieved by purchasing a 15x eyepiece and a 100x objective. Anything that magnifies more will not noticeably add resolution, since at magnifications of about 2000–2500 × the so-called “optical limit”, due to diffraction phenomena, is already close.

The next important point is the type of nozzle. Usually there are monocular, binocular and trinocular varieties. The principle of classification is based on how many eyes you want to look at an object. In the case of a monocular system, you have to squint, constantly changing eyes from fatigue during prolonged observation. Here you will come to the aid of a binocular attachment, which, as its name implies, you can look with both eyes. In general, this will have a more favorable effect on the well-being of your eyes. Should not be confused binocular with a stereo microscope. The latter makes it possible to achieve volumetric perception of the observed object due to the presence of two lenses, while binocular microscopes simply feed the same image to both eyes. For photo and video shooting of micro-objects, you will need a “third eye”, namely a nozzle for installing the camera. Many manufacturers produce special cameras for their models of microscopes, although you can use a regular camera (although you will have to buy an adapter).

Observation at high magnifications requires good illumination due to the small aperture of the corresponding objectives. Gone are the days when the drug was examined in the light reflected from the mirror. Now microscopes are complex optical-mechanical-electrical devices, in which the achievements of scientific and technological progress are fully used. Modern devices have their own light bulb, the light from which propagates through special device - condenser, - which illuminates the drug. Depending on the type of condenser, one can distinguish various ways observations, the most popular of which are light and dark field methods. The first method, familiar to many from school, assumes that the preparation is illuminated evenly from below. At the same time, in those places where the drug is optically transparent, light propagates from the condenser to the lens, and in an opaque medium, light is absorbed, becomes colored and scattered. Therefore, a dark image is obtained on a white background - hence the name of the method.

With a dark-field condenser, everything is different. It is designed so that the rays of light coming out of it are directed in different directions, except for the lens opening itself. Therefore, they pass through an optically transparent medium without falling into the field of view of the observer. On the other hand, the rays that hit an opaque object are scattered on it in all directions, including in the direction of the lens. Therefore, as a result, a light object will be visible on a dark background. This method of observation is good for studying transparent objects that are not contrasting against a light background. By default, most microscopes are brightfield. Therefore, if you plan to expand the range of observation methods, then you should choose microscope models that provide for the installation of additional equipment: condensers, phase contrast devices, polarizers, etc.

As you know, optical systems are not ideal: the passage of light through them is associated with image distortions - aberrations. Therefore, they try to make lenses and eyepieces in such a way that these aberrations are eliminated as much as possible. All this affects their final cost. For reasons of price and quality, it makes sense to buy plan achromatic lenses. They are used in professional research and have an adequate price. Objectives with high magnification (for example, 100x) have a numerical aperture greater than 1, which implies the use of oil in observation - the so-called immersion. Therefore, if, in addition to “dry” lenses, you also take immersion lenses, you should take care of the immersion oil in advance. Its refractive index must necessarily match your particular lens.

Of course, this is not the whole list of parameters that should be considered when buying a microscope. Sometimes it is important to pay attention to the design and location of the stage and handles to control it. It is worth choosing the type of illuminator, which can be either an ordinary incandescent lamp or an LED that shines brighter and heats up less. Microscopes can also individual characteristics. But the main thing that should be said about their device, perhaps, has been said. Each additional option is an addition to the price, so the choice of model and configuration is the lot of the end user.

Recently, there has been a trend of buying microscopes for children. Such devices are usually monoculars with a small set of lenses and modest parameters, are inexpensive and can serve as a good Starting point not only for direct observations, but also for familiarization with the basic principles of the microscope. After that, the child will already be able to buy a more serious device based on the conclusions made when working with the "budget" model.

How to watch?

Amateur observation does not require exceptional skills either in working with a microscope or in preparing preparations. Of course, you can buy far from cheap sets of ready-made preparations, but then the feeling of your personal presence in the study will not be so bright, and sooner or later ready-made preparations will get bored. Therefore, having bought a microscope, it is worth thinking about real objects for observation. In addition, you will need, though special, but affordable means for the preparation of preparations.

Observation in transmitted light assumes that the object under study is sufficiently thin. Not even every peel from a berry or fruit in itself has the necessary thickness, therefore sections are examined in microscopy. At home, fairly adequate cuts can be made with ordinary shaving blades. With some skill, it is possible to achieve a slice thickness of several cell layers, which will greatly increase the differentiability of specimen objects. Ideally, you should work with a monocellular layer of tissue, because several layers of cells superimposed on each other create a fuzzy and chaotic image.

The test preparation is placed on a glass slide and, if necessary, covered with a coverslip. Therefore, if glasses are not included with the microscope, they should be purchased separately. This can be done at the nearest medical equipment store. However, not every preparation adheres well to the glass, so fixation methods are used. The main fixings are fire and alcohol. The first method requires a certain skill, since you can simply "burn" the drug. The second way is often more justified. It is not always possible to get pure alcohol, so you can buy an antiseptic in a pharmacy as a substitute, which, in fact, is alcohol with impurities. It is also worth buying iodine and greenery there. These disinfectants, which are familiar to us, actually turn out to be good dyes for preparations. After all, not every drug reveals its essence at first sight. Sometimes he needs to “help” by tinting his shaped elements: nucleus, cytoplasm, organelles.

To take blood samples, you should purchase scarifiers, pipettes and cotton wool. All this is on sale in medical stores and pharmacies. In addition, to collect objects from the wild, stock up on small bags and jars. Taking a jar with you to collect water from the nearest body of water when going out into nature should become a good habit for you.

What to watch?

The microscope has been purchased, the instruments have been purchased - it's time to start. And you should start with the most accessible. What could be more accessible than peel onion(fig. 1 and 2)? Being thin in itself, the onion peel, being tinted with iodine, reveals clearly differentiated nuclei in its structure. This experience, well known from school, is perhaps worth doing first. The onion peel itself must be poured with iodine and left to stain for 10-15 minutes, after which you need to rinse it under running water.

In addition, iodine can be used to color potatoes (Fig. 3). Do not forget that the cut must be made as thin as possible. Literally 5–10 minutes of a potato cut in iodine will show starch layers that will turn into blue color. Iodine is a fairly versatile dye. They can stain a wide range of preparations.

Figure 1. Onion skin(magnification: 1000×). Stained with iodine. In the photograph, the nucleus in the cell is differentiated.

Figure 2. Onion peel(magnification: 1000×). Stained with Azur-Eosin. In the photograph, the nucleolus differentiates in the nucleus.

Figure 3. Grains of starch in potatoes(magnification: 100×). Stained with iodine.

On the balconies residential buildings a large number of corpses of flying insects often accumulate. Do not rush to get rid of them: they can serve as valuable material for research. As you can see from the photographs, you will find that insect wings are hairy (Figure 4-6). Insects need this so that the wings do not get wet. Due to the high surface tension, water drops cannot “fall through” through the hairs and touch the wing.

This phenomenon is called hydrophobicity. We talked about it in detail in the article "Physical hydrophobia". - Ed.

Figure 4. Ladybug's wing(magnification: 400×).

Figure 5. Bibionid wing(magnification: 400×).

Figure 6. Hawthorn Butterfly Wing(magnification: 100×).

If you have ever touched the wing of a butterfly or a moth, then you probably noticed that some kind of “dust” flies off it. The photographs clearly show that this dust is scales from their wings (Fig. 7). They have different shape and quite easy to tear.

In addition, you can superficially study the structure of the limbs of arthropods (Fig. 8), consider chitinous films - for example, on the back of a cockroach (Fig. 9). With proper magnification, one can be convinced that such films consist of tightly adhering (possibly fused) flakes.

Figure 7. Scales from the wings of a moth(magnification: 400×).

Figure 8. Spider limb(magnification: 100×).

Figure 9. Film on the back of a cockroach(magnification: 400×).

The next thing to watch is the peel of berries and fruits (Fig. 10 and 11). Not all fruits and berries have a peel acceptable for microscope observation. Either her cellular structure may not be differentiable, or the thickness will not allow you to achieve a clear image. One way or another, you have to make a lot of attempts before you get good drug. You will have to sort through different varieties of grapes - for example, in order to find one with coloring substances in the skin that would be "pleasing to the eye" form, or make several cuts of the skin of a plum, until you achieve a monocellular layer. In any case, the reward for the work done will be worthy.

Figure 10. Skin of black grapes(magnification: 1000×).

Figure 11. Plum peel(magnification: 1000×).

Figure 12. Clover leaf(magnification: 100×). Some cells contain a dark red pigment.

A fairly accessible object for research is greenery: grass, algae, leaves (Fig. 12 and 13). But, despite the ubiquity, choose and cook good sample happens not so easy.

The most interesting thing about the greenery is perhaps the chloroplasts (Figures 14 and 15). Therefore, the cut must be extremely thin. Often, green algae found in any open reservoirs have an acceptable thickness.

Figure 13. Strawberry leaf(magnification: 40×). Figure 16. Floating algae with a flagellum(magnification: 400×).

Figure 17. Baby snail(magnification: 40×).

Figure 18. Blood smear. Stained with Azur-Eosin according to Romanovsky (magnification: 1000×). The photo shows an eosinophil against the background of erythrocytes.

a scientist himself

Video 1. Snail heartbeat(optical microscope magnification 100×).

After researching simple and affordable drugs, the natural desire is to complicate observation techniques and expand the class of objects under study. To do this, first, you need literature on special methods research, and, secondly, special means. These tools, although they are specific for each type of object, still have some generality and universality. For example, the well-known method of Gram stain, when different types bacteria after staining are differentiated by colors; it can also be used when staining other, non-bacterial cells. Close to it, in fact, is the method of staining blood smears according to Romanovsky. On sale there is both a ready-made liquid dye and a powder consisting of dyes such as azure and eosin. All dyes can be bought in specialized biomedical stores, or ordered online. If, for some reason, you cannot get a blood dye, you can ask the laboratory assistant doing your blood test in the hospital to attach a glass with a stained smear of your blood to the analysis.

Continuing the theme of blood testing, one cannot fail to mention the Goryaev camera - a device for counting blood cells. Being an important tool for assessing the number of erythrocytes in the blood back in the days when there were no devices for automatic analysis of its composition, the Goryaev camera also allows you to measure the size of objects thanks to the markings applied to it with known sizes divisions. Methods for examining blood and other fluids using the Goryaev camera are described in special literature.

Conclusion

In this article, I tried to consider the main points related to the choice of a microscope, improvised means and the main classes of objects for observation, which are easy to meet in everyday life and in nature. As already mentioned, special observation tools require at least basic skills in working with a microscope, so their review is beyond the scope of this article. As you can see from the photos, microscopy can become a pleasant hobby, and maybe even an art for someone.

AT modern world, where various technical means and the devices are in walking distance, everyone decides for himself what to spend his own money on. For entertainment reasons, it can be an expensive laptop or a TV with an outrageous diagonal size. But there are also those who take their gaze away from the screens and direct it either far into space, acquiring a telescope, or, looking into the eyepiece of a microscope, penetrate deep inside. Inside the nature of which we are a part.

Literature

1. Landsberg G.S. (2003). Optics. § 92 (p. 301);
2. Gurevich A.A. (2003). Freshwater algae;
3. Kozinets G.I. (1998). Atlas of blood cells and bone marrow;
4. Korzhevsky D.E. (2010). Fundamentals of histological technique..

Stanislav Yablokov, Yaroslavl State University. P. G. Demidova

For two years now I have been observing the microworld at home, and for a year I have been filming it with a camera. During this time, I saw with my own eyes how blood cells look, scales falling from the wings of butterflies, how the heart of a snail beats. Of course, a lot could be learned from textbooks, video lectures and thematic sites. But at the same time there would be no feeling of presence, proximity to what is not visible to the naked eye. That these are not just words from a book, but personal experience. An experience that is available to everyone today.

Onion peel. Magnification 1000×. Stained with iodine. The photo shows the cell nucleus.

Onion peel. Magnification 1000×. Stained with azure-eosin. In the photograph, a nucleolus is visible in the nucleus.

Potato. Blue spots are grains of starch. Magnification 100×. Stained with iodine.

Film on the back of a cockroach. Magnification 400×.

Plum peel. Magnification 1000×.

Bibionid bug wing. Magnification 400×.

The wing of a hawthorn butterfly. Magnification 100×.

Scales from the wings of a moth. Magnification 400×.

Chloroplasts in grass cells. Magnification 1000×.

Baby snail. Magnification 40×.

Clover leaf. Magnification 100×. Some cells contain a dark red pigment.

Strawberry leaf. Magnification 40×.

Chloroplasts in algal cells. Magnification 1000×.

Blood smear. Stained with azure-eosin according to Romanovsky. Magnification 1000×. In the photo: eosinophil on the background of erythrocytes.

Blood smear. Stained with azure-eosin according to Romanovsky. Magnification 1000×. In the photo: on the left - a monocyte, on the right - a lymphocyte.

What to buy

The theater begins with a hanger, and microphotography with the purchase of equipment, and above all, a microscope. One of its main characteristics is the set of available magnifications, which are determined by the product of the magnifications of the eyepiece and the objective.

Not every biological specimen is good for viewing at high magnification. This is due to the fact that the greater the magnification of the optical system, the smaller the depth of field. Consequently, the image of uneven surfaces of the drug will be partially blurred. Therefore, it is important to have a set of objectives and eyepieces that allows you to observe with a magnification from 10-20 to 900-1000×. Sometimes it is justified to achieve a magnification of 1500x (15x eyepiece and 100x objective). A larger magnification is meaningless, since the wave nature of light does not allow you to see finer details.

The next important point is the type of eyepiece. With how many eyes do you want to view the image? Usually, monocular, binocular and trinocular varieties are distinguished. In the case of a monocular, you will have to squint, tiring the eye during prolonged observation. Look into the binocular with both eyes (it should not be confused with a stereo microscope, which gives a three-dimensional image). For photo and video filming of micro-objects, you will need a “third eye” - a nozzle for installing equipment. Many manufacturers produce special cameras for their microscope models, but you can also use a regular camera by purchasing an adapter for it.

Observation at high magnifications requires good illumination due to the small aperture of the objectives. The light beam from the illuminator, converted in an optical device - a condenser, illuminates the preparation. Depending on the nature of the illumination, there are several methods of observation, the most common of which are the methods of light and dark fields. In the first, the simplest, familiar to many from school, the preparation is illuminated evenly from below. In this case, through the optically transparent parts of the preparation, light propagates into the lens, and in opaque parts it is absorbed and scattered. On a white background, a dark image is obtained, hence the name of the method. With a dark-field condenser, everything is different. The light beam coming out of it has the shape of a cone, the rays do not fall into the lens, but are scattered on an opaque preparation, including in the direction of the lens. As a result, a light object is visible on a dark background. This observation method is good for studying transparent low-contrast objects. Therefore, if you plan to expand the range of observation methods, you should choose microscope models that provide for the installation of additional equipment: a dark-field condenser, a dark-field diaphragm, phase contrast devices, polarizers, etc.

Optical systems are not ideal: the passage of light through them is associated with image distortions - aberrations. Therefore, they try to make lenses and eyepieces in such a way that these aberrations are eliminated as much as possible. All this affects their final cost. For reasons of price and quality, it makes sense to buy plan achromatic lenses for professional research. Strong objectives (for example, 100× magnification) have a numerical aperture greater than 1 when using immersion, high refractive oil, glycerol solution (for UV), or just water. Therefore, if, in addition to “dry” lenses, you also take immersion lenses, you should take care of the immersion liquid in advance. Its refractive index must necessarily correspond to a particular lens.

Sometimes you should pay attention to the design of the stage and handles to control it. It is worth choosing the type of illuminator, which can be either an ordinary incandescent lamp or an LED, which is brighter and heats up less. Microscopes also have individual characteristics. Each additional option is an addition to the price, so the choice of model and configuration is up to the consumer.

Today, they often buy inexpensive microscopes for children, monoculars with a small set of objectives and modest parameters. They can serve as a good starting point not only for the study of the microcosm, but also for familiarization with the basic principles of the microscope. After that, the child should already buy a more serious device.

How to watch

You can buy far from cheap sets of finished drugs, but then the feeling of personal participation in the study will not be so bright, and they will get bored sooner or later. Therefore, care should be taken both about the objects for observation and about the available means for the preparation of preparations.

Observation in transmitted light assumes that the object under study is sufficiently thin. Even the peel of a berry or fruit is too thick, so sections are examined under microscopy. At home, they are made with ordinary razor blades. In order not to crush the peel, it is placed between pieces of cork or filled with paraffin. With some skill, you can achieve a slice thickness of several cell layers, and ideally, you should work with a monocellular layer of tissue - several layers of cells create a fuzzy, chaotic image.

The test preparation is placed on a glass slide and, if necessary, covered with a coverslip. You can buy glasses in a medical equipment store. If the preparation does not adhere well to the glass, it is fixed by slightly moistening with water, immersion oil or glycerin. Not every drug immediately opens its structure, sometimes it needs “help” by tinting its shaped elements: nuclei, cytoplasm, organelles. Good dyes are iodine and greenery. Iodine is a fairly versatile dye; it can stain a wide range of biological preparations.

When going out into nature, you should stock up on jars for collecting water from the nearest reservoir and small bags for leaves, dried insect residues, etc.

What to watch

The microscope has been purchased, the instruments have been purchased - it's time to start. And you should start with the most accessible - for example, onion peel. Thin in itself, tinted with iodine, it reveals clearly distinguishable cell nuclei in its structure. This experience, familiar from school, should be done first. Onion peel should be poured with iodine for 10-15 minutes, then rinsed under running water.

In addition, iodine can be used to color potatoes. The cut must be made as thin as possible. Literally 5-10 minutes of his stay in iodine will show layers of starch, which will turn blue.

The balconies often accumulate a large number of corpses of flying insects. Do not rush to get rid of them: they can serve as valuable material for research. As you can see from the photos, you will find that insects have hairs on their wings that protect them from getting wet. The high surface tension of water does not allow the drop to "fall" through the hairs and touch the wing.

If you have ever touched the wing of a butterfly or a moth, then you probably noticed that some kind of “dust” flies off it. The pictures clearly show that this is not dust, but scales from the wings. They have different shapes and are quite easy to tear off.

In addition, using a microscope, you can study the structure of the limbs of insects and spiders, consider, for example, chitinous films on the back of a cockroach. And with proper magnification, make sure that such films consist of tightly fitting (possibly fused) scales.

An equally interesting object to observe is the peel of berries and fruits. However, either its cellular structure may be indistinguishable, or its thickness will not allow for a clear image. One way or another, many attempts will have to be made before a good preparation is obtained: sorting through different varieties of grapes to find one in which the coloring substances of the skin would have an interesting shape, or making several cuts of the skin of a plum, achieving a monocellular layer. In any case, the reward for the work done will be worthy.

Grass, algae, leaves are even more accessible for research. But, despite the ubiquity, choosing and preparing a good drug from them can be difficult. The most interesting thing about greenery is, perhaps, chloroplasts. Therefore, the cut must be extremely thin.

Acceptable thickness is often found in green algae found in any open water bodies. There you can also find floating algae and microscopic aquatic inhabitants - snail fry, daphnia, amoebas, cyclops and shoes. A small baby snail, optically transparent, allows you to see your own heartbeat.

self explorer

After studying simple and affordable preparations, you will want to complicate the observation technique and expand the class of objects under study. This will require both special literature and specialized tools, which are different for each type of object, but still have some universality. For example, the Gram stain method, when different types of bacteria begin to differ in color, can be applied to other, non-bacterial cells. Close to it is the method of staining blood smears according to Romanovsky. On sale there is both a ready-made liquid dye and a powder consisting of its components - azure and eosin. They can be bought in specialized stores or ordered online. If you can’t get the dye, you can ask the laboratory assistant who does the blood test for you at the clinic for a glass with a stained smear.

Continuing the topic of blood research, we should mention the Goryaev camera - a device for counting the number of blood cells and assessing their size. Methods for examining blood and other fluids using the Goryaev camera are described in special literature.

In the modern world, where a variety of technical means and devices are within walking distance, everyone decides for himself what to spend money on. It can be an expensive laptop or a TV with an exorbitant diagonal size. There are also those who take their eyes off the screens and direct it far into space, acquiring a telescope. Microscopy can become an interesting hobby, and for some even an art, a means of self-expression. Looking into the eyepiece of a microscope, one penetrates deep into that nature, of which we ourselves are a part.

"Science and Life" about microphotography:

Microscope "Analit" - 1987, No. 1.

Oshanin S. L. With a microscope at the pond. - 1988, No. 8.

Oshanin S. L. Life invisible to the world. - 1989, No. 6.

Miloslavsky V. Yu. - 1998, No. 1.

Mologina N. . - 2007, No. 4.

Glossary for the article

Aperture- the effective opening of the optical system, determined by the dimensions of mirrors, lenses, diaphragms and other parts. The angle α between the extreme rays of a conical light beam is called the angular aperture. Numerical aperture A = n sin(α/2), where n is the refractive index of the medium in which the object of observation is located. The resolution of the device is proportional to A, the illumination of the image is A 2 . To increase the aperture, immersion is used.

Immersion- a transparent liquid with a refractive index n > 1. The preparation and the microscope objective are immersed in it, increasing its aperture and thereby increasing the resolution.

plan achromatic lens- A chromatic aberration corrected lens that produces a flat image across the entire field. Ordinary achromats and apochromats (aberrations corrected for two and for three colors respectively) give a curvilinear field that cannot be corrected.

Phase contrast- method microscopic studies, based on the change in the phase of a light wave that has passed through a transparent preparation. The phase of the oscillation is not visible to the naked eye, so special optics - a condenser and a lens - turn the phase difference into a negative or positive image.

Monocytes- one of the forms of white blood cells.

Chloroplasts- green organelles plant cells responsible for photosynthesis.

Eosinophils- blood cells that play a protective role in allergic reactions.