What properties are characteristic of ethylene. Ethylene is a colorless gas with a sweetish odor. Industrial ethanol production

With a friend there is a double connection.

1. Physical properties

Ethylene is a colorless gas with a faint pleasant odor. It is slightly lighter than air. It is slightly soluble in water, but soluble in alcohol and other organic solvents.

2. Structure

Molecular formula C 2 H 4. Structural and electronic formulas:

3. Chemical properties

Unlike methane, ethylene is chemically quite active. It is characterized by addition reactions at the site of the double bond, polymerization reactions and oxidation reactions. In this case, one of the double bonds is broken and a simple single bond remains in its place, and due to the released valences, other atoms or atomic groups are added. Let's look at this using examples of some reactions. When ethylene is passed into bromine water (an aqueous solution of bromine), the latter becomes discolored as a result of the interaction of ethylene with bromine to form dibromoethane (ethylene bromide) C 2 H 4 Br 2:

As can be seen from the diagram of this reaction, what occurs here is not the replacement of hydrogen atoms with halogen atoms, as in saturated hydrocarbons, but the addition of bromine atoms at the site of the double bond. Ethylene also discolors easily purple aqueous solution potassium manganate KMnO 4 even at normal temperature. Ethylene itself is oxidized into ethylene glycol C 2 H 4 (OH) 2. This process can be represented by the following equation:

• 2KMnO 4 -> K 2 MnO 4 + MnO 2 + 2O

The reactions of ethylene with bromine and potassium manganate serve to open unsaturated hydrocarbons. Methane and other saturated hydrocarbons, as already noted, do not interact with potassium manganate.

Ethylene reacts with hydrogen. So, when a mixture of ethylene and hydrogen is heated in the presence of a catalyst (nickel, platinum or palladium powder), they combine to form ethane:

Reactions in which hydrogen is added to a substance are called hydrogenation or hydrogenation reactions. Hydrogenation reactions have a large practical significance. They are quite often used in industry. Unlike methane, ethylene burns with a swirling flame in air because it contains more carbon than methane. Therefore, not all carbon burns at once and its particles become very hot and glow. These carbon particles are then burned in the outer part of the flame:

• C 2 H 4 + 3O 2 = 2CO 2 + 2H 2 O

Ethylene, like methane, forms explosive mixtures with air.

4. Receipt

Ethylene does not occur in nature, with the exception of minor impurities in natural gas. In laboratory conditions, ethylene is usually produced by the action of concentrated sulfuric acid on ethanol when heated. This process can be represented by the following summary equation:

During the reaction, water elements are subtracted from the alcohol molecule, and the two valences removed saturate each other to form a double bond between the carbon atoms. For industrial purposes, ethylene is obtained in large quantities from petroleum cracking gases.

5. Application

In modern industry, ethylene is used quite widely for the synthesis of ethyl alcohol and the production of important polymeric materials (polyethylene, etc.), as well as for the synthesis of other organic substances. A very interesting property of ethylene is to accelerate the ripening of many vegetable and garden fruits (tomatoes, melons, pears, lemons, etc.). Using this, the fruits can be transported while still green, and then brought to a ripe state at the point of consumption by introducing small amounts of ethylene into the air of the warehouse.

Ethylene is used to produce vinyl chloride and polyvinyl chloride, butadiene and synthetic rubbers, ethylene oxide and polymers based on it, ethylene glycol, etc.

Notes

Sources

• F. A. Derkach "Chemistry" L. 1968

? V ? Phytohormones

? V ? Hydrocarbons

The people of the British Isles are known to be passionate people. Having at one time put half the world under their control, they did not forget about the simple joys of life. About apples, for example. In the mid-to-late 19th century and early 20th, apple breeding reached its peak, but for the connoisseur, selection and varieties are not the only variety. Being a connoisseur means not only crunching on your favorite variety and knowing a couple of others, but also, for each variety, observing the development of the taste and texture of the apple during its ripening and storage. We often don’t think about the fact that a fruit is a living organism with complex biochemistry and its own hormones. Even the fruit has already been picked from the plant. One of the simplest hormones in structure, one of the most important and therefore the most studied is the plant ripening hormone ethylene (C 2 H 4). Ethylene – chief assistant all fruit distribution. You collect bananas while they are still hard and easily transportable, but green, astringent and inedible in their raw form, and send them ten thousand kilometers to anywhere in the world. Then you either wait until, under the influence of a naturally released ripening hormone, they ripen, become soft and aromatic, or if you need to sell them right now, you create an artificial ethylene atmosphere.

Ethylene, in fact, is a plant hormone with a broad effect; it regulates plant growth, leaf fall, and flower opening. But it is interesting for us precisely as a fruit ripening hormone.

Fruits are the only food that nature intended as food. This is the plant's way of spreading its seeds over a wide area. But only on the condition that the fruit is eaten by the distributors at the moment when the seeds are ready to germinate. And the plant regulates this through maturation. The biochemistry of this process is complex, but it is obvious. Color change due to the breakdown of chlorophyll into colored pigments anthocyanins and carotenoids, breakdown of tasteless polysaccharides into sweet sugars, accumulation aromatic compounds, breakdown of cell wall pectins with observed softening of the fruit.

In a wide group of plants, these processes can occur in the fruit even after it has been picked from the plant and the supply of nutrients has ceased. These fruits have already accumulated enough initial substances to trigger ripening. And this maturation is caused by the hormone ethylene. In the scientific literature, such fruits are called climacteric, these are apples, bananas, tomatoes, etc.

For another group of fruits, ripening is possible only on a branch with access to nutrients plants. This group includes pineapples and citrus fruits. After picking, they no longer ripen.

Ethylene is an invisible gas with a very weak odor of its own, so at home the ripening processes look a little mystical - you put a banana on the shelf and wait a week for it to ripen, put it in a closed bag and you need to wait less. This is because ethylene works on the principle of positive feedback - it is released by the fruit itself and acts as a hormone on the same fruit, bananas release a lot of ethylene, they are almost champions in this. With damage, lack of water and other stresses, the release of ethylene increases. It is said that this fact was known back in Ancient Egypt, when to ripen figs, several fruits were cut on the branches.
According to its chemical structure, ethylene is the simplest alkene and one of the most common chemical substances, generally produced in the world, competing with sulfuric acid. Of course, not for the sake of fruit ripening. For example, as a monomer of polyethylene.

The hormonal regulation system is one of the most important systems in plants and includes phytohormones. Phytohormones are compounds through which the interaction of cells, tissues and organs is carried out and which, in small quantities, are necessary for the launch and regulation of physiological and morphogenetic programs. Plant hormones are relatively low molecular weight organic matter. They are formed in various tissues and organs and act in very low concentrations of the order of 10 -13 -10 -5 mol/l.

All phytohormones are divided into stimulants and inhibitors. Inhibitors (from the Latin “Inhibeo” - I stop, restrain) in biology, natural and synthetic substances that inhibit the activity of enzymes (both in the body and in cell-free systems); differ in the nature of action, specificity and other properties. Ethylene is a growth inhibitor. A number of compounds have a similar effect on the plant, but are inferior in effectiveness. Ethylene is the only gaseous plant growth regulator.

Ethylene gas (C2H4) is rightly classified as a plant hormone, since it is synthesized in plants and in extremely low concentrations regulates their growth, activates fruit ripening, causes aging of leaves and flowers, abscission of leaves and fruits, participates in the response of plants to various stress factors and in the regulation of many other important events in the life of a plant (Kulaeva, 1995). Ethylene, or more precisely, ethylene producers - compounds whose destruction is accompanied by the release of ethylene, are widely used in practice Agriculture. All this determines the great attention of biochemists, physiologists, geneticists, molecular biologists and practitioners to the study of ethylene.

IN last years Great progress has been made in obtaining and studying mutant plants that are insensitive to ethylene. These mutants have provided progress in isolating the genes responsible for the perception and transmission of the ethylene signal in plants, and have helped to partially decipher the molecular pathways through which the signal passes, causing the activation or suppression of certain physiological programs. This success prompted the author to write an article about ethylene. Its purpose is to consider the regulatory role of ethylene in plants, its practical application, features of its biosynthesis, as well as the latest data on the mechanism of action of this phytohormone.

History of the discovery of ethylene

Ethylene was first obtained by the German chemist Johann Becher in 1680 by the action of oil of vitriol on wine alcohol. At first it was identified with “flammable air,” i.e., hydrogen. Later, in 1795, ethylene was obtained in a similar way by the Dutch chemists Deyman, Potts van Truswyk, Bond and Lauerenburg and described it under the name “oil gas”, since they discovered the ability of ethylene to add chlorine to form an oily liquid - ethylene chloride (“Dutch oil”). chemists").

The study of the properties of ethylene, its derivatives and homologues began in the mid-19th century. Start practical use These compounds were founded on the classical studies of A.M. Butlerov and his students in the field of unsaturated compounds and especially Butlerov’s creation of the theory of chemical structure. In 1860, he prepared ethylene by the action of copper on methylene iodide, establishing the structure of ethylene.

In 1901, Dmitry Nikolaevich Nelyubov grew peas in a laboratory in St. Petersburg, but the seeds produced twisted, shortened sprouts, the top of which was bent with a hook and did not bend. In the greenhouse and in the fresh air, the seedlings were even, tall, and the top quickly straightened the hook in the light. Nelyubov proposed that the factor causing the physiological effect was in the air of the laboratory.

At that time, the premises were lit with gas. The same gas burned in the street lamps, and it was noticed long ago that in the event of an accident in the gas pipeline standing nearby When gas leaks occur, trees turn yellow prematurely and shed their leaves.

The illuminating gas contained a variety of organic substances. To remove gas impurities, Nelyubov passed it through a heated tube with copper oxide. In the “purified” air, the pea seedlings developed normally. In order to find out which substance causes the response of the seedlings, Nelyubov added various components of the illuminating gas in turn, and discovered that the addition of ethylene causes:

1) slower growth in length and thickening of the seedling,

2) “non-bending” apical loop,

3) change in the orientation of the seedling in space.

This physiological response of seedlings was called the triple response to ethylene. Peas turned out to be so sensitive to ethylene that they began to be used in biotests to determine low concentrations of this gas. It was soon discovered that ethylene also causes other effects: leaf fall, fruit ripening, etc. It turned out that plants themselves are able to synthesize ethylene, i.e. ethylene is a phytohormone.

Physiological role of ethylene

Properties of ethylene

Ethylene is a colorless gas with a faint, barely noticeable odor. It is poorly soluble in water (at 0 0 25.6 ml of ethylene dissolves in 100 g of water), burns with a luminous flame, and forms explosive mixtures with air. Thermally less stable than methane. Already at temperatures above 350 0 ethylene partially decomposes into methane and acetylene. At a temperature of about 1200 0 dissociates mainly into acetyl and hydrogen.

Ethylene is not found in natural gases (with the exception of volcanic gases). It is formed mainly during the pyrogenetic decomposition of natural compounds containing organic substances.

In very low concentrations, on the order of 0.001-0.1 µl/l, it is capable of inhibiting and changing the nature of plant growth and accelerating fruit ripening. Ethylene is synthesized in bacteria, fungi, lower and higher plants, and in large quantities. Not all organisms are capable of synthesizing ethylene. Thus, of the 228 species of microscopic fungi studied, only 25% emit ethylene. Organisms control the rate of ethylene synthesis. This regulates its concentration; in addition, excess ethylene can freely diffuse into environment. The rate of ethylene formation varies in different organs and systems. Ethylene production increases with aging and falling of leaves and fruits. It is inhibited by a lack of oxygen (in all agricultural plants except rice) and can be regulated by temperature and light. Affects ethylene synthesis and CO 2 levels. Moreover, in different plants carbon dioxide can both stimulate and inhibit the formation of ethylene.

As shown in the experiments of D.N. Nelyubov, ethylene inhibits the growth of the stem in length and causes its thickening. Subsequently, scientists found that this occurs due to a change in the direction of growth of stem cells, which corresponds to a change in the orientation of the cytoskeletal elements. Ethylene suppresses root growth and accelerates aging, which is clearly visible on the leaves and flowers of plants. Ethylene also accelerates the ripening of fruits and causes leaves and fruits to fall off. It induces the formation of a special separating layer of cells in the petiole, along which the leaf is torn off from the plant, and at the site of the tear, instead of a wound, an ethylene-induced protective layer of cells with suberized walls remains. This phytohormone influences flower sex by causing the production of female flowers in plants characterized by separate female and male flowers, such as cucumber, pumpkin and squash.

The formation of roots on the stem and the formation of a special tissue in the stem - aerenchyma, through which oxygen enters the roots, are induced by ethylene. This saves plants in conditions of oxygen starvation of the roots, into which they find themselves when the soil is flooded. In addition, ethylene causes other changes in plants. For example, epinasty, which changes the angle of inclination of the leaf relative to the stem (leaves droop).

Ethylene is also involved in plant responses to various damaging influences - mechanical, chemical and biological. It is involved in plant response to pathogen attack. Ethylene includes plant defense systems against pathogens. At the same time, it induces the synthesis of a large number of enzymes, for example, enzymes that destroy the cell wall of fungi (chitinases, specific glucanases), as well as enzymes involved in the synthesis of phytoalexins - compounds that are toxic to the pathogen.

When plants are injured, ethylene is synthesized and released. There is evidence that when animals eat the leaves of woody plants, the eaten plant releases ethylene and, under its influence, substances can be synthesized in the leaves of neighboring plants that make the leaves unpalatable to animals.

Ethylene biosynthesis

The key compound for ethylene biosynthesis in plants is the amino acid methionine. When methionine interacts with the high-energy compound ATP, the intermediate product S-adenosylmethionine appears, which is further converted into 1-aminocyclopropane-1-carboxylic acid (ACC), the direct precursor of ethylene in plants. ACC then decomposes in the presence of oxygen to form ethylene, ammonia, formic acid and CO2. Each step is catalyzed by a specific enzyme. The key enzyme at the level of which ethylene biosynthesis is regulated is ACC synthase. ACC synthase is not constantly synthesized in cells, but is induced by inducers - substances that cause its synthesis. Such enzymes are usually called inducible. The synthesis of ACC synthase is induced by high concentrations of auxin, molecules - chemical signals of fungal infection, as well as ethylene itself. The synthesis of ACC synthase continues as long as the inducer is present. Then the synthesis stops, and the formed enzyme molecules are quickly destroyed, since their half-life is 20-30 minutes. This highlights how tightly the plant controls ethylene synthesis at the level of formation and destruction of the key biosynthetic enzyme ACC synthase.

It is significant that in the plant genome there is a large family of ACC synthase genes, which differ in their regulation: some are turned on at different stages of normal plant development, others - upon wounding, others - under the action of a pathogen, etc. This provides a multifactorial system for regulating ethylene synthesis in plants. The ACC synthase and ACC oxidase genes attract much attention from genetic engineers, since modification of plants using these genes makes it possible to regulate ethylene synthesis and, consequently, regulate the rate of fruit ripening. Along this path, American genetic engineers obtained transgenic tomato plants with a month-long shelf life for fruits.

The next stage of ethylene biosynthesis comes down to the oxidation of ACC. It is oxygen-dependent and does not occur under conditions of oxygen starvation (anaerobiosis). This situation occurs in the roots when the soil is flooded. Without oxygen, root respiration, ATP synthesis and processes dependent on it are suppressed. The supply of shoots with water, mineral nutrients, hormones (cytokinins) and other waste products of the root is disrupted. All this threatens the death of plants. And then the ethylene protection system turns on. Under conditions of anaerobiosis, the conversion of ACC into ethylene in the roots stops. ACC enters as part of the sap - a solution that flows from the roots to the shoots, to the above-ground organs, where there is no lack of O2, and is converted there into ethylene. Ethylene induces epinasty in the shoots - a change in the angle of inclination of the petiole to the stem, as a result of which the leaves fall down and move away from the direct action of sunlight. At the same time, the leaves heat up less and evaporate less water. Ethylene induces the formation of roots on stems, which do not perform an absorbent function, but carry out specific synthetic processes necessary for the normal functioning of the shoot, including restoring the supply of above-ground organs with cytokinins. In addition, ethylene induces the formation of aerenchyma in the stem - tissue through which O2 passes from the stems to the roots and ensures their normal functioning. This example well illustrates how ethylene ensures the adaptation of plants to conditions of oxygen deficiency in the root zone that occurs when the soil is flooded.

During normal plant life, ethylene is actively synthesized in ripening fruits and aging leaves. This is understandable: it induces fruit ripening, senescence and leaf fall. However, a high level of ethylene synthesis is also characteristic of meristematic tissues - zones of cell division. This is still difficult to explain. Ethylene synthesis in plants is caused by high concentrations of auxin, which occurs at the level of induction of ACC synthase genes. Synthesized ethylene suppresses reactions caused by auxin. For example, in a certain concentration range, auxin activates root growth. Their excess induces the synthesis of ethylene, which suppresses root growth. Thus, ethylene is included in the plant's feedback control of auxin action. Ethylene plays the same role in plant reactions to high concentrations of cytokinins.

Ethylene as a mechanical stress hormone

The release of ethylene is closely related to the mechanical effect on plant cells. Let's take the example of the response of a pea seedling, which Nelyubov observed. Until the sprout reaches the surface, the delicate cells of the apical meristem must be protected from damage. Therefore, bending and formation of an apical loop occurs. It is not the meristem that grows through the soil, but the stronger underlying portion.

When a mechanical obstacle (a stone) appears in the path of the seedling, the seedling releases more ethylene, growth in length stops and thickening begins. The seedling strives to overcome the obstacle by increasing the pressure. If this is successful, the ethylene concentration drops and length growth is restored. But if the obstacle is too large, then ethylene production is further enhanced. The seedling deviates from the vertical and goes around the pebble.

In the air, the ethylene concentration drops, the seedlings unbend the apical meristem, and leaf development begins.

Ethylene and touch

Up until 1991, plant physiologists had a sketchy understanding of exactly how plants sense touch. Using the method of subtracting c-DNA libraries, it was found that spraying Arabidopsis thaliana plants with water causes the synthesis of new messenger RNAs - after 10-15 minutes their level increased hundreds of times.

Spraying is a complex factor: air humidity changes, a shadow from water vapor is created, and, finally, the leaves are subjected to mechanical stress. Each of the factors was studied separately. It turned out that humidity does not play any role, but if the plant is rubbed with a glass rod, it will sense it and respond within 10-15 minutes by expressing new mRNAs. The discovered genes were designated as TCH1, TCH2, TCH3, TCH4, TCH5 (from English touch).

If, without touching the plant, you suddenly cover it with a black cap, then the level of TCH matrices in it also increases. The creation of sufficiently powerful sound effects did not lead to the desired result: TCH messenger RNAs did not appear in the cells.

What are the genes responsible for, the products of which appear in cells when touched? They turned out to be very similar to the well-known calcium-binding proteins - calmodulins. These proteins, together with Ca 2+, activate the cytoskeleton and promote the transition from sol to gel of many structures in the plant cell. Plants that were often disturbed with a glass rod noticeably lag behind in growth compared to those that were not touched, but they turn out to be mechanically stronger and hardened.

The protein product of the TCH 4 gene turned out to be a xyloglucan endotransglycosylase. The synthesis of this protein can also be induced by brassinosteroids. The same effects can be caused by adding ethylene. At the same time, the synthesis of Ca-binding TCH proteins also occurs.

Ethylene and wound healing

Many plants form laticifers that contain latex (natural rubber). However, rubber does not “freeze” inside the lacticifers (just as blood does not coagulate in the vessels). But if the plant is damaged, latex appears on the surface, which quickly hardens and clogs the site of damage. Latex glues spores of fungi and bacteria, hardens in the mouthparts of insects, or glues them to a droplet of protruding rubber.

For a long time, nothing would have been known about what causes latex to quickly harden when a plant is damaged if it were not for the requests of agriculture. On Hevea plantations, hardening of latex is a harmful process: you have to re-make notches on tree trunks, place vessels for collecting rubber in new places, which creates a lot of unnecessary work.

It turned out that latex hardens under the influence of ethylene. A minor latex protein, hevein, plays an important role in this process. Latex hardening can be combated to some extent by treating plants with ethylene synthesis inhibitors. The most well-known inhibitor is silver ions, but there are cheaper ones. Thus, in rubber plants, ethylene promotes the healing of mechanical damage.

In addition, under the influence of ethylene, a special tissue, the wound periderm, is activated. A cork cambium is formed, which forms a layer of suberinized cork that separates healthy (living) tissue from diseased (dead) tissue. The plug is highly hydrophobic, which effectively prevents the spread of fungi and bacteria entering the wound and protects healthy tissue from excessive evaporation.

The size and location of wound periderm formation differ in different plants. Thus, the lungwort forms a wound periderm a few millimeters from the area of ​​damage (for example, by mushrooms). The area of ​​the leaf surrounded by the wound periderm falls out.

In beans, the wound periderm at the base of the leaf blade is activated, and the plant sacrifices the damaged part of the complex leaf for the sake of the safety of the whole plant.

It would seem that the wound periderm can only be useful when attacked by bacteria and fungi. However, it also plays an important role during attacks by insects and ticks. Under the influence of ethylene, local “leaf fall” occurs - the damaged leaf falls to the ground along with the pest. Pests have less chance of reaching the crown again. Protective “leaf fall” is observed, for example, in roses when attacked by spider mites.

Regulation of leaf fall in temperate latitudes

Ethylene regulates the phenomenon of leaf fall. This reaction has so impressed plant physiologists that ethylene is sometimes considered a plant aging hormone. The phenomenon of leaf fall is not just aging. So, in the tropics, individual leaves live 3-4 years (often more). The reduction in leaf lifespan is associated with a protective reaction to mechanical stress.

When leaves fall, many open wounds are formed at the attachment points. In order for the leaf to separate without harm to the whole plant, a separating layer is formed at its base. Its work is almost identical to the work of the wound periderm. The site of future damage is closed with a cork, the overlying tissue loosens and becomes fragile, and the leaf falls off. To loosen the cell wall, pectinases are released into it. When pectin is broken down, physiologically active substances are released - oligosaccharins, which stimulate further softening of cell walls.

Leaves that are preparing to fall transfer nitrogen compounds and carbohydrates to other parts of the plant. Chlorophyll is destroyed and the leaf turns yellow. Harmful substances accumulate in the tissues, which will be removed from the plant by leaf fall.

Thus, the phenomena of leaf fall and protection from damage are closely related. In the case of leaf fall in temperate latitudes, we see an advanced physiological reaction. In winter, the leaves are damaged by frost and snow falls on them, causing increased mechanical stress on the branches. The plant, as it were, “anticipates” future mechanical stress and frees itself from leaves in advance. Therefore, it is not surprising that all processes associated with leaf loss in areas with cold and snowy winters are under the control of ethylene (Prokhorov, 1978).

Formation and ripening of fruits

The beginning of the life of the fetus lies in the flower, more precisely in the ovary. Pollen grains land on the surface of the stigma, they begin to germinate and mechanically press on the conductive tissue of the style in order to reach the ovules hidden deep in the pistil. Naturally, when pollen germinates, the style tissues begin to release ethylene.

Different parts of the flower respond differently to the ethylene signal. Thus, all organs that attracted pollinating insects either die off or change color. Within a few hours after pollination, morning glory petals lose turgor and wither. The separating layer at the base of the tepals of the lily is activated and they fall off (compare with the phenomenon of leaf fall). In lungwort, the pH (acidity) of the vacuolar sap changes and the flowers turn from pink to blue. In calla palustris, ethylene causes the inflorescence cover to change color from white to green. Subsequently, the plant uses the spathe as an additional source of photoassimilates for developing fruits. Note that in some cases, ethylene causes the destruction of chlorophyll, yellowing and falling of leaves, while in others, it enhances photosynthesis.

The stamens wither under the influence of ethylene, and the ovaries begin to actively grow, attracting new nutrients.

Ethylene is especially important at the last stage of ripening of juicy fruits. Almost all the effects considered “play” here. The fruit stops growing (like a seedling that has encountered an obstacle), the cells of the fruit begin to secrete pectinases into the apoplast - the fruits become soft. In addition, physiologically active fragments of pectin - oligosaccharins - are formed. In the legs of the fruit, the separating layer is activated and a wound periderm is formed (as during leaf fall), the pH changes - the fruits become less acidic, and their color also changes from green to more yellow or red (like the petals of some plants).

Note that damaged fruits ripen and fall earlier than others. Mechanical stress is caused by birds, insect larvae or phytopathogenic fungi. As in the case of leaves, the plant strives to discard the poor-quality fruit so that the remaining fruits are as healthy as possible.

Fruit ripening under the influence of ethylene is the same proactive physiological reaction as leaf fall. The juicy fruits are distributed by birds and mammals, which damage the fruits when eaten, and the plant pre-produces ethylene.

The property of accelerating fruit ripening was discovered in ethylene a long time ago, back in the 20s, and since then it has been widely used. During transportation, it is important that the fruits remain firm and green. To do this, they are transported in ventilated containers, protecting the fruits from mechanical damage that causes ethylene synthesis. In addition, ethylene biosynthesis slows down at low temperatures and at high concentrations of carbon dioxide in the air. In principle, it would be possible to use inhibitors of ethylene biosynthesis, if not for their toxicity to humans. The only place where inhibitors can be used is in the storage of cut flowers. In Holland, flowers are placed not in ordinary water, but in a special solution, which, in addition to mineral salts, photosynthesis products and antiseptics, contains ethylene synthesis inhibitors. With the help of such additives, merchants manage to keep bouquets fresh for many days.

To prevent ethylene from being formed in fruits, mutants with impaired ethylene biosynthesis are obtained. Tomato varieties based on such mutants have already been obtained. These tomatoes can be stored for a very long time and transported over long distances. Shortly before sale, they are treated with ethylene, and the fruits ripen quickly. However, this technology significantly reduces the taste of the fruit.

There is a saying that one rotten apple spoils the whole barrel. This is true. A rotten apple produces ethylene, which causes tissue softening in other apples. Moreover, each fruit begins to produce its own ethylene as it ripens, and a “chain reaction” of ethylene production begins in the barrel.



Answer: Ethylene is the most important representative of a number of unsaturated hydrocarbons with one double bond: formula -
The gas is almost odorless and poorly soluble in water. In the air it burns with a luminous flame. Thanks to the availability
- ethylene bonds easily enter into addition reactions:
(dibromoethane)
(ethyl alcohol) Due to the presence of a double bond, ethylene molecules can connect with each other, forming long chains (from many thousands of original molecules). This reaction is called a polymerization reaction:
Polyethylene is widely used in industry and in everyday life. It is very inactive, does not break, and is processed well. Examples: pipes, containers (barrels, boxes), insulating material, packaging film, glass, toys and much more. Other protozoa unsaturated hydrocarbon is polypropylene:
When it polymerizes, polypropylene is formed - a polymer. The polymer is similar in its overall properties and application to polyethylene.

Polypropylene is stronger than polyethylene, so many parts for a variety of machines are made from it, as well as many precision parts, for example, for excavators. Approximately 40% of polypropylene is processed into fibers.

Among vegetable growers who are engaged in the cultivation and supply of agricultural crops professionally, it is customary to collect fruits that have not passed the ripening stage. This approach allows you to preserve vegetables and fruits longer and transport them over long distances without problems. Since green bananas or, for example, tomatoes are unlikely to be in serious demand among the average consumer, and natural ripening can take a long time, gases are used to speed up the process ethylene And acetylene. At first glance, this approach may cause bewilderment, but delving into the physiology of the process, it becomes clear why modern vegetable growers actively use such technology.

Gas ripening hormone for vegetables and fruits

The influence of specific gases on the rate of ripening of crops was first noticed by the Russian botanist Dmitry Nelyubov, who at the beginning of the 20th century. determined a certain dependence of the “ripeness” of lemons on the atmosphere in the room. It turned out that in warehouses with an old heating system, which was not highly airtight and allowed steam to escape into the atmosphere, lemons ripened much faster. Through a simple analysis, it was found that this effect was achieved thanks to ethylene and acetylene, which were contained in the steam emanating from the pipes.

At first, such a discovery was deprived of due attention from entrepreneurs; only rare innovators tried to saturate their storage facilities with ethylene gas to improve productivity. Only in the middle of the 20th century. The “gas hormone” for vegetables and fruits has been adopted by fairly large enterprises.

To implement the technology, cylinders are usually used, the valve system of which allows you to accurately adjust the gas output and achieve the required concentration in the room. It is very important that in this case ordinary air, which contains oxygen, the main oxidizing agent for agricultural products, is displaced from the storage facility. By the way, the technology of replacing oxygen with another substance is actively used to increase the shelf life of not only fruits, but also other food products - meat, fish, cheeses, etc. Nitrogen and carbon dioxide are used for this purpose, as discussed in detail.

Why is ethylene gas called "banana" gas?

So, the ethylene environment allows you to speed up the ripening process of vegetables and fruits. But why is this happening? The fact is that during the ripening process, many crops emit a special substance, which is ethylene, which, when released into the environment, affects not only the source of the emission itself, but also its neighbors.

this is how apples help with ripening

Each type of fruit produces different amounts of ripening hormone. The biggest differences in this regard are:

• apples;
• pears;
• apricots;
• bananas.

The latter enter our country over a considerable distance, so they are not transported in ripe form. In order for banana peels to acquire their natural bright yellow color, many entrepreneurs place them in a special chamber that is filled with ethylene. The cycle of such treatment is on average 24 hours, after which the bananas receive a kind of impetus to accelerated ripening. It is interesting that without such a procedure, the favorite fruit of many children and adults will remain in a semi-ripe state for a very long time. Therefore, “banana” gas is simply necessary in this case.

sent for ripening

Methods for creating the required gas concentration in the fruit storage chamber

It was already noted above that to ensure the required concentration of ethylene/acetylene in the storage room for vegetables and fruits, gas cylinders are usually used. In order to save money, some vegetable growers sometimes resort to another method. In the room with the fruits, a piece of calcium carbide is placed, onto which water drips at intervals of 2-3 drops/hour. As a result chemical reaction Acetylene is released, gradually filling the internal atmosphere.

This “old-fashioned” method, although attractive in its simplicity, is more typical for private households, since it does not allow achieving the exact concentration of gas in the room. Therefore, in medium and large enterprises, where it is important to calculate the required amount of “gas hormone” for each crop, balloon installations are often used.

Correct formation gas environment plays a huge role in the storage and production of food products, making it possible to improve the appearance of the product, its taste and increase its shelf life. Read more about methods of packaging and storing products in a series of articles about food gas mixtures, and you can order these products by selecting the required gas and, if desired, receiving advice on its proper use.