And how they change their color in the fall. Molecules responsible for the bright shades of yellow and orange are no longer a mystery, but why the leaves turn red is still a mystery.

Reacting to change in air temperature and less daylight, the leaves stop producing chlorophyll(which gives the color green), which absorbs blue and partly red light emitted from the sun.

Since chlorophyll is sensitive to cold, some changes in weather, such as early frosts, will "turn off" its production faster than usual.

Why do leaves turn yellow and fall

During this time, orange and yellow pigments called carotenoids(which can also be found in carrots) and xanthophylls shine through leaves that have no green left.

"The yellow color is present in the leaves all summer long, but it is not visible until the green disappears," says Paul Schaberg(Paul Schaberg), plant physiologist with the US Forest Service.

But scientists still have little information about the red color that appears on some leaves in the fall.

The color red is known to come from anthocyanides, which, unlike carotenoids, are produced only in autumn. Anthocyanides also give color to strawberries, red apples and plums.

Trees release anthocyanins when they sense a change in their environment - frost, ultraviolet radiation, drought and / or fungus.

But the red leaves are also a sign of illness wood. If you notice that the leaves of the tree turned red earlier than usual (at the end of August), most likely the tree is suffering from a fungus, or it was damaged somewhere by a person.

Why does a tree waste its energy to produce new anthocyanidins in a leaf when that leaf is about to fall off?

Paul Schaberg believes that if anthocyanides help the leaves stay on the tree longer, they can help the tree absorb more nutrients before the leaves fall off. The tree can use the soaked resources to bloom in the next season.

Anthocyanins

The topic of anthocyanins is a little more difficult to study than the rest of the components of trees. While all trees contain chlorophyll, carotene, and xanthophylls, not all produce anthocyanins. Even trees that have anthocyanins only produce them under certain conditions.

Before the tree gets rid of its leaves, it tries to absorb as much as possible. more nutrients of them [leaves], at which point anthocyanin comes into play.

Scientists have several answers to the question of why some trees produce this substance, and the leaves change their color.

The most common theory suggests that anthocyanins protect the leaves from excess sunlight, while allowing the tree to absorb the nutrients stored in the leaves.

On wood, these pigments play the role of sunscreen blocking dangerous radiation and protecting the leaves from an overabundance of light. They also protect cells from freezing quickly. Their benefits can be compared to those of antioxidants.

A lot of sunlight, dry weather, frosty weather, low nutrient levels and other stressors increase the concentration of sugar in tree sap... This triggers the production of large amounts of anthocyanins in a final attempt to store energy to survive the winter.

Scientists believe that the study of anthocyanins help to understand the level of the disease every tree. This, in turn, will provide a clearer picture of environmental problems in the future.

As the character of the book and cartoon said Lorax: "The color of the trees will one day be able to tell us how the tree is feeling at the moment."

Why do leaves dry and fall

With the arrival of winter, part of the globe receives less sunshine and the air gets colder. When these changes occur, the trees prepare for winter.

The trees that cast their leaves clog the attachment points of the leaves... This does not allow liquids with useful substances to reach the leaves, which is why the leaves change their color and fall off.

Leaf fall symbolizes not only the change of season, this process also helps the tree survive the cold, dry winter air.

In winter, trees do not receive enough liquid to "contain" leaves... If they didn’t clog the places where the leaves begin to grow, the trees would simply die.

When spring brings warm air and water, the trees begin to grow new leaves.

Why don't conifers shed their leaves?

In spring and summer, the leaves of trees are green due to the large amount of green substance they contain - chlorophyll... Chlorophyll plays a very important role. Using water and sunlight, it provides nourishment for the entire tree. Is happening photosynthesis- the process of the formation of sugar in the light in chloroplasts, which then turns into starch.

In spring and summer, during the period of active growth and development of plants, chlorophyll is found in large quantities in the leaves, staining them in a bright green color. In addition to green chlorophyll, there are other substances in smaller quantities in the leaves - yellow, orange and red, in addition, the walls of the cells that form the leaf are brown. But all these colors are drowned out by green and therefore practically invisible.

With the onset of cold weather, the channels that transported juices to and from the leaf gradually close. This reduces the amount of water entering the leaf and decreases the amount of chlorophyll. Then, hitherto invisible shades of various substances and veins begin to appear. The leaves suddenly turn into amazing yellow-red, purple, brown colors. Leaves that have lost chlorophyll will no longer be able to turn green again. The season of golden autumn is coming.

With the arrival of autumn, the length of daylight hours decreases. Consequently, the process of photosynthesis also does not have sufficient time to develop. The process of photosynthesis is important for obtaining nourishment for trees. So it turns out that the tree receives less and less nutrients, which entails a slowdown in all processes.

Chlorophyll begins to break down, the green color in the leaves becomes less and less visible. Now comes the turn of other color pigments: yellow xanthophyll, orange carotene and red anthocyanin. Thanks to these pigments, the leaves acquire such a bright color.

Probably everyone noticed that not all trees "dress" in the same way in autumn. In some colors, crimson tones prevail, in some - yellow, and in some - brown. For example, the leaves of maples and aspens are colored crimson. The leaves of lindens, oaks and birches are cast in gold.

It is interesting that the leaves of alder and lilac do not have time to change their color, they fall off still green. Why? Because the leaves of these trees lack any coloring pigments, except for chlorophyll.

All life processes in trees slow down with the arrival of autumn, the vitality of the leaves is extinguished. And this process is eternal, like life itself, and just as natural and irreversible. That is, those leaves that have already lost their green chlorophyll pigment will no longer be able to regain their strength.

The leaf coloring process can be divided into three stages:

1. The beginning of the change in the color of the leaves. Some leaves turn yellow;
2. Changing the color of tree crowns. The tops begin to dazzle and differ markedly from the rest of the crown;
3. Complete change in leaf color. Almost the entire crown has changed its color.

Leaf fall is the shedding of all harmful substances. The leaves accumulate a large amount of nutrients. However, in addition to useful substances, harmful substances also accumulate in the leaves - metabolites, excess mineral salts, which only harm the health of the tree. Autumn is the time when the tree begins to get rid of the harmful ones present in the leaves, and leaves the useful ones for the winter.

In addition, scientists have proven that in winter, when there are no leaves on the crown, the tree has little chance of suffering from drought. The reason is that the leaves take up a lot of moisture, and the roots cannot cope with its lack.

When are the brightest leaf colors?

The brightest, juicy colors of the leaves are in the fall, when the cold, dry and sunny weather lasts for a long time (at temperatures from 0 to 7 degrees Celsius, the formation of anthocyanin increases). Beautiful leaf colors in the fall are found in places like Vermont. But, for example, in Great Britain, where the climate is rainy and the weather is cloudy almost all the time, autumn leaves are most often dull yellow or brown. Autumn is passing, winter is coming. Together with the leaves, the plants also lose their colorful colors.

The leaves are attached to the branches with special cuttings. With the onset of winter cold, the connection between the cells that make up the cuttings disintegrates. After that, the leaves remain connected to the branch only by thin vessels, through which water and nutrients enter the leaves. A light breeze or a drop of rain can break this ephemeral connection and the leaves will fall to the ground, adding another touch of color to the multicolored thick carpet of fallen leaves. Plants store food for winter, like chipmunks and squirrels, but they accumulate it not in the ground, but in branches, trunks and roots.

Leaves, into which water ceases to flow, dry up, fall from the trees and, caught by the wind, circle in the air for a long time until they lie down on forest paths, lining them with a crisp path. The yellow or red color of the leaves can persist for several weeks after they have fallen off. But over time, the corresponding pigments are destroyed. The only thing that remains is tannin (yes, it is he who colors the tea).

Why do leaves change color in autumn? Experiment

In order to find the answer to the question why in autumn the leaves on the trees change color and turn yellow, children will need to collect some leaves.

After that, together you must sort them by color into prepared containers. After that, the leaves are poured with alcohol and ground. Once chopped and mixed, the rubbing alcohol will help the color to appear even better.

Hint: The time it takes for the color to completely absorb will depend on how much leaves and alcohol were used. After 12 hours, the liquid may not yet be completely absorbed, but the effect is already evident. As the liquid is absorbed into the filter, the colors from the leaves diverge.

Explanation of the experiment why leaves change color

In winter, the days get shorter, which reduces the amount of sunlight for the leaves. Due to the lack of sun, the plants go into a dormant stage and feed on glucose that they have accumulated over the summer. As soon as the "winter mode" turns on, the green color of chlorophyll leaves the leaves. And as the bright green tint fades away, we begin to see yellow and orange colors. Small amounts of these pigments were present in the leaves at all times. For example, maple leaves are bright red because they contain excess glucose.

Why do leaves on trees turn yellow in summer?

The main nutrients required for the development of a tree are:

• Magnesium;
• Potassium;
• Phosphorus;

Magnesium may not be sufficient on sandy and sandy soils. Often its imbalance manifests itself in wet weather, with frequent watering - magnesium is quickly washed out.

There is not enough potassium in the leaves, if, in addition to yellowness, a red rim is noticeable on the leaf plate. Lack of potassium is accompanied by a simultaneous lack of phosphorus.

Phosphorus starvation manifests itself in the appearance of a bronze tint and the leaves dry out, covering the entire surface of the leaf.

Feeding the potting mix with the missing ingredients will solve the problem.

Waterlogged soil

The close occurrence of groundwater and waterlogging of the soil due to frequent watering will affect the stagnation of water, the decomposition of oxygen. Fruit trees in the garden will begin not only to turn yellow, but also to dry out, wither, it is possible that the root system will rot. Soil drainage, an increase in the level of planting, and normalization of care will help solve the problem.

Chlorosis of fruit trees

With the development of chlorosis, the leaves of fruit trees become dull, pale, turn yellow, as if there is no sun in the garden.

Chlorosis can appear for many reasons:

• Excess lime level in the soil;
• Excessive amount of fresh manure;
• Lack of iron salts (chlorophyll is not formed);
• Freezing of roots;
• Oxygen starvation (due to waterlogging);

If chlorosis did not manage to cover the entire crown of the tree, then it is necessary to restore the gap in the care that caused chlorosis, and also feed it with a solution of ferrous sulfate (2%).

Pests and diseases of fruit trees

When aphids or mites appear, the leaves not only turn yellow in the summer at the trees in the garden - deformed shoots appear. Similar symptoms can occur with the development of fungal diseases. In order for the garden trees to be healthy, it is necessary to carry out prophylaxis by spraying with solutions before and after flowering.

Damage to the bark of garden trees in summer

In summer, garden trees begin to turn yellow if their bark or root system was previously mechanically damaged. This could have happened when replanting, loosening the soil, pruning or cultivating. Due to the disruption of the vital functions of the tissues of the tree, a general wilting occurs. It is difficult to determine the problem in this case. To restore a fruit tree in the garden in the summer, either top dressing or the use of biological preparations to cover wounds will help.

Unlike animals, which receive the substances and energy necessary for life from the food they eat, ordinary plants consume three separate flows of matter / energy, namely:

• minerals and water - come through the root system;
• carbon dioxide, necessary for biomass synthesis - comes from the ambient air through the leaves;
• energy - absorbed by the leaves from the flow of sunlight falling on them.

The assimilation of light energy is possible only due to its interaction with colored substances (plant pigments) in the process of photosynthesis. The main photosynthetic pigments in plants are chlorophylls, which give plants their green color. For the photosynthesis of different groups of substances (carbohydrates, proteins), chlorophyll absorbs the blue and red components of the solar spectrum, ignoring the green as "unnecessary" (the real process is even more complicated and interesting - as can be seen from photographs of living plants in the near infrared spectrum).

The rest of the pigment groups (yellow xanthophylls, orange carotenes, as well as red, purple and blue anthocyanins) are present in the plant leaf in small amounts. They can be seen in etiolated (grown without light and therefore lacking chlorophyll) plants or parts of them - for example, in potato shoots sprouting in the dark. Chromophoric groups of chlorophyll molecules responsible for the absorption of parts of the light spectrum are very "gentle": a slight chemical / physical effect can destroy them quite easily - this process is clearly visible during cooking, when greens are scalded, fried or thrown into boiling soup.

What happens to foliage in autumn?

Preparing for the period of winter dormancy, the plant, if possible, "pumps out" all potentially useful substances from the biomass of the leaves and stops the synthesis of chlorophylls. Their residual amount in the leaf becomes so small that it can no longer mask the presence of other, more stable coloring pigments and the own color of the cell walls (it is diverse, but typically has a brown tint). Therefore, the withering leaf acquires the color shade that the dyes remaining in the leaf blade provide it, and in proportion to their quantity / concentration - and it is precisely because of this that the autumn forest is colored in such varied and bright colors.

How does a plant "know" about the onset of autumn?

In a living plant, many "internal clocks" are simultaneously functioning - processes tied to the influence of external factors (cyclical fluctuations in temperature, light, and so on). With regard to the leaf, the most important factor here is the relative (as a fraction of the entire daily cycle) and absolute (in hours) duration of daylight hours - this is how the process of preparing the plant for the winter dormant period starts. In addition to changes in biochemical processes, in deciduous trees at the base of the leaf, the growth of cells of the cork layer is initiated, which gradually interrupts the connection between the leaf and the tree - and the leaf falls off.

Why in the fall the leaves turn yellow and fall

The summer season ends with the last fallen leaves from trees and shrubs. For many people, bare plants cause despondency and yearning for summer. But autumn is beautiful! No wonder there are so many poetic lines dedicated to this time of the year. Why do the leaves of some plants turn red, while others turn yellow? And why do the leaves fall?

Leaf fall is the brightest sign of autumn. These plants adapt to the unfavorable conditions of the season. Seasonal plant variability begins in northern latitudes and gradually moves south. Leaf fall repeats every year and always delights us with its bright colors - from yellow and orange to pink and purple. Leaves fly even from evergreens in the subtropics and tropics. Only there they do not fall all at once, but gradually throughout the year, and from that it is not so noticeable.

It gets colder in autumn, and water flows into the plants from the roots to the leaves in slow motion. But this is not the main reason for leaf fall. The onset of unfavorable conditions is a signal for the transition of plants to a new cycle of life, which is embedded in the genetic code. This indicates to us that the fall-off of leaves is not a direct consequence of unfavorable conditions. Together with the winter dormant period, it enters the very cycle of plant development. There is also a way to make sure that leaf fall is a physiological process. Why is the leaf separating from the branch? It turns out that with the onset of cold weather at the base of the petiole, where the leaf is attached by a “leaf pad” to the branch, a cork layer is formed. The cells of this layer have smooth walls and are easily separated from each other. As soon as the wind blows a little harder, and the leaf is separated from the cork layer.

The green color of the leaves in summer is due to the large amount of chlorophyll pigment they contain. This pigment "feeds" the plants, because it is with its help that in the light the plant synthesizes organic substances from carbon dioxide and water, and first of all the main sugar - glucose, and from it - all other nutrients. Chlorophyll contains iron, and when it breaks down, oxides are formed, which have a brown-yellow color. The destruction of chlorophyll occurs more intensely in the light, that is, in sunny weather. That is why, in a cloudy rainy autumn, the leaves retain their green color longer. When sunny days come in autumn, the leaves take on a golden-red color.

However, along with chlorophyll, green leaves also contain other pigments - yellow xanthophyll and orange carotene (which determines the color of carrot roots). In summer, these pigments are invisible, as they are masked by a large amount of chlorophyll. In autumn, as the vital activity in the leaf fades, chlorophyll is gradually destroyed. This is where the yellow and red shades of xanthophyll and carotene appear in the leaf.

In addition to gold, the autumnal outfits of trees contain crimson hues. This color is responsible for a pigment called anthocyanin. Unlike chlorophyll, anthocyanin is not bound inside the cell with plastic formations (grains), but is dissolved in the cell sap. With a decrease in temperature, as well as in bright light, the amount of anthocyanin in the cell sap increases. In addition, stopping or delaying the synthesis of nutrients in foliage also stimulates the synthesis of anthocyanins.

Fallen leaves can retain their shape and color for a few more days, and then they begin to dry out and acquire a brown color, not very pleasant to the eye. Part of the leaves remains in place under trees and shrubs, and part of the wind blows off the site. For aesthetic reasons, the gardener is often tempted to clear the soil of fallen leaves. Is it necessary? After all, the leaves contain the same chemical compounds that were taken from the soil by plants. True, they acquired a slightly different chemical composition and entered the organic matter formed by the plant. Once on the surface of the soil, the leaves become "prey" for a great variety of different living organisms. Among them, the most important role in leaf utilization belongs to earthworms. Their waste products (excrement of worms are called caprolites) contain the entire set of nutrients for plants in almost finished form. So the leaves, having got into the biological cycle of substances, returned to the soil, what they once received in the plant.

Now decide for yourself - to remove the foliage from under the trees or not? There are two ways to preserve the beneficial properties of fallen leaves. The first is to leave it in place until spring, followed by digging. In this case, the leaves will insulate the topsoil. The second path will be somewhat more difficult and take longer. Collect the leaves in a compost pit and after a year or two return them under the trees in a rotten state.

V. A. Rassypnov , professor of ASAU

Our pets need constant care and attention. With their lack, plants begin to suffer and give alarming signs. One of these signs is the yellowing of the leaves of your indoor pets. Consider why the leaves on indoor flowers turn yellow and what to do in this case.

In case of illness or improper care, our pets react primarily by the fact that the edges or the entire leaf plate turn yellow entirely. Let's consider the main reasons for the occurrence of such phenomena.

Even a novice florist understands that yellowing of foliage is an alarming sign.

Improper home care

The most common causes of yellow spots on indoor flowers are home care mistakes.

Excessive watering of the plant

Moderate watering will be sufficient for most flowers. Before purchasing this or that copy, first of all, you need to familiarize yourself with the conditions of its maintenance and the rules of care.

Excessive hydration leads to waterlogging of the soil and decay of the root system. As a result, leaves and shoots turn yellow, the plant may die if measures are not taken in time for treatment.

Insufficient watering

Often, an overdried earthen lump becomes the reason for the yellowing of the leaves of indoor flora. In this case, the plant does not receive enough nutrients and moisture. The tips of the leaves and branches begin to dry out and fall off, the roots die off.

Drafts

Almost all indoor flowers, especially tropical ones, do not tolerate drafts. They should be kept away from any source of flower draft - open windows, air conditioners, fans, etc.

Our favorite split systems can damage the immunity of flowers.

Temperature drops

Yellowing of the shoots of the plant can react to sudden temperature changes... During the acclimatization period, our green friends usually get sick.

Lack of light

From insufficient sunlight, the leaves begin to turn yellow on the side which flower is turned to the shade.

Sunburn

When exposed to direct sunlight, yellow spots usually appear on the leaves.

Failure to comply with the feeding regime

With a lack or excess of nutrients in the soil, leaves in plants begin to turn yellow along the central vein, mainly at the top of the flower.

Diseases and pests

Often, parts of plants turn yellow under the influence of diseases or pests.

1. Fungal diseases... As a result of late blight or anthracnose infection, the leaf blades may turn yellow.
2. Infectious diseases... In this case, yellow spots appear on the foliage.
3. Pest infestation... Among such insects are thrips, spider mites, aphids, whiteflies. The spider mite sucks the juices from the leaves and shoots, as a result of which they turn yellow and subsequently fall off.

Reasons for the appearance of a spider mite on indoor flowers

The first sign of flower damage is the appearance of white dots on the foliage. In the future, you can see the cobweb in internodes and on the leaves.

If a spider mite is wound up on one copy, then it can easily move to neighboring flowers... It means that we urgently need to get rid of it.

First, you need to familiarize yourself with the rules for caring for each indoor flower. Since plants are individual, the care of different species will differ significantly.

If irrigation is causing the leaves to turn yellow, adjust it to suit your green friend's needs. In the case when the flower is flooded, you need to remove it from the pot.

Examine the roots removing damaged and rotten... Transplant the flower into dry disinfected soil. Keep track of your watering schedule.

When the leaves turn yellow from lack or excess of sunlight, it is enough to move the pot with the plant to another windowsill or into the back of the room.

If there is a lack or excess of fertilizers in the soil, it is necessary to replenish the balance: either add the required substances with dressings, or transplant the flower. If there is an excessive amount of fertilizer in the substrate, you need to clear the root system from the soil and transplant the plant into fresh soil.

Transplanting into new soil is one of the key measures in getting rid of the pest

When the leaves turn yellow from drafts and temperature extremes, you need to monitor the temperature regime of keeping your pets. When airing, it is recommended to take the plants into the next room.

Pest control

At the first sign of pest damage to a plant, isolate it so as not to infect nearby flowers.

First of all, you need to remove all affected leaves and stems of the plant. It is no longer possible to save them, but the rest can be protected in this way.

does not tolerate humid environments, therefore, you need to spray the plant with warm water as often as possible or arrange a shower for him. Rubbing the leaves with soapy water is also an effective method.

At the end of the treatment, the leaves are thoroughly washed off. After that, wrap the flower pot in a transparent bag and place it in a sunny place. After two to three days, the plant can be opened.

If there is an advanced case of damage to a flower by pests, in no way not do without the use of insecticides... To get rid of spider mites, acaricides are used.

When treating plants with chemicals, be sure to use personal protective equipment - a mask and gloves.

For humans, Fitoverm, Vermit, Aktofit can be considered less dangerous. But they only neutralize adults without harming the eggs. Therefore, after 7-10 days, it is recommended to re-process the flower in order to destroy the offspring.

Due to the popularity of insecticides, we have introduced.

In order to help your favorite plants, you need to closely monitor their condition. At the first signs of illness or discomfort, determine the reasons that caused them.

Based on possible reasons, it is necessary provide the required assistance to flowers in a short time so that they continue to delight with lush flowering and a healthy look.