In spring and summer, the leaves of trees are green due to the large amount of green matter they contain - chlorophyll. Chlorophyll plays a very important role. Using water and sun rays, it produces food for the entire tree. Happening photosynthesis- the process of formation of sugar in light in chloroplasts, which is then converted 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, coloring them bright green. In addition to green chlorophyll, the leaves contain other substances in smaller quantities - 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 are therefore practically invisible.
With the onset of cold weather, the channels that carried juices into and out of the leaf gradually close. This reduces the amount of water entering the leaf and reduces the amount of chlorophyll. Then previously invisible shades of various substances and veins begin to appear. The leaves suddenly turn into amazing yellow-red, crimson, and brown colors. Leaves that have lost chlorophyll will not be able to turn green again. The golden autumn season is coming.
With the arrival of autumn, the length of daylight hours decreases. Consequently, the process of photosynthesis also does not have enough time to develop. The process of photosynthesis is important for trees to obtain food. So it turns out that nutrients the tree receives less and less, which entails a slowdown of all processes.
Chlorophyll begins to break down, and less and less green color is visible in the leaves. Now comes the turn of other color pigments: yellow xanthophyll, orange carotene and red anthocyanin. Thanks to these pigments, the leaves acquire such bright colors.
Probably everyone has noticed that not all trees “dress” the same in the fall. Some colors are dominated by crimson tones, some are yellow, and some are brown. For example, the leaves of maples and aspens turn purple. The leaves of linden, oak and birch trees are cast in gold.
It is interesting that the leaves of alder and lilac do not have time to change color; they fall off while still green. Why? Yes, because the leaves of these trees do not contain any coloring pigments other than chlorophyll.
All life processes in trees slow down with the arrival of autumn, life force leaves are fading. And this process is eternal, like life itself, and just as natural and irreversible. That is, those leaves that have already lost their green pigment chlorophyll will no longer be able to regain their strength.
The leaf coloring process can be divided into three stages:
- Beginning of leaf color change. Some leaves are turning yellow;
- Change in color of tree crowns. The tops begin to become variegated and noticeably different from the rest of the crown;
- Complete change in leaf color. Almost the entire crown has changed its color.
The falling of leaves is the dropping of all harmful substances. Accumulates in leaves large number nutrients. However, in addition to beneficial 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 leaves contained in it, 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, richest colors of the leaves occur in autumn, when cold, dry and sunny weather lasts for a long time (at temperatures from 0 to 7 degrees Celsius, the formation of anthocyanin increases). There are beautiful fall leaf colors 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 passes, winter comes. Along with the leaves, the plants also lose their colorful colors.
The leaves are attached to the branches by special cuttings. With the onset of winter cold, the connection between the cells that make up the cuttings disintegrates. After this, the leaves remain connected to the branch only by thin vessels, through which water and nutrients enter the leaves. A slight breath of wind 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 multi-colored 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.
The leaves, into which water stops flowing, dry out, fall from the trees and, caught by the wind, circle in the air for a long time until they settle on the forest paths, lining them with a crisp path. The yellow or red coloration of the leaves may persist for several weeks after they have fallen. But over time, the corresponding pigments are destroyed. The only thing that remains is tannin (yes, this is what colors the tea).
Why do leaves change color in autumn? Experiment
In order to find the answer to the question of why the leaves on trees change color and turn yellow in the fall, children will need to collect some leaves.
After which you must sort them together by color into prepared containers. After this, the leaves are filled with alcohol and ground. Once crushed and stirred, the alcohol will help the color come out even better.
Tip: The time it takes for the color to fully absorb will depend on how much leaf and alcohol was used. After 12 hours, the liquid may not yet be completely absorbed, but the effect is already obvious. As the liquid is absorbed into the filter, the colors from the leaves disperse.
Explanation of the experiment why leaves change color
During winter, the days become shorter, reducing the amount of sunlight available to the leaves. Due to lack of sun, plants go into a dormant stage and feed on the glucose they accumulated over the summer. As soon as the “winter mode” is turned on, the green color of chlorophyll leaves the leaves. And as bright green tint disappears, we begin to see yellow and orange colors. Small amounts of these pigments were present in the leaves all along. For example, maple leaves bright red because they contain excess glucose.
Why do leaves on trees turn yellow in summer?
The main nutrients needed for tree development are:
- Magnesium;
- Potassium;
- Phosphorus;
Magnesium may be deficient in sandy loam and sandy soils. Often its imbalance manifests itself in humid weather, with frequent watering - magnesium is quickly washed out.
The leaves do not have enough potassium if, in addition to yellowness, a red rim is noticeable on the leaf plate. A 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 soil mixture with the missing ingredients will solve the problem.
Soil waterlogging
Close occurrence groundwater and waterlogging of the soil due to frequent watering will affect water stagnation, oxygen decomposition. Fruit trees in the garden will not only begin to turn yellow, but also dry out and wither, and it is possible that the root system will rot. The problem will be solved by soil drainage, increasing the planting level, and normalizing care.
Chlorosis of fruit trees
With the development of chlorosis, the leaves of fruit trees become dull, pale, and turn yellow, as if there is no sun in the garden.
Chlorosis can appear for many reasons:
- Exceeding the level of lime in the soil;
- Excessive amounts of fresh manure;
- Lack of iron salts (chlorophyll is not formed);
- Freezing of roots;
- Oxygen starvation (due to waterlogging);
If chlorosis has not managed to cover the entire crown of the tree, then it is necessary to restore the gap in care that caused chlorosis, and also feed with a solution of ferrous sulfate (2%).
Pests and diseases of fruit trees
When aphids or mites appear, the leaves of the trees in the garden not only turn yellow in the summer, but deformed shoots appear. Similar symptoms may appear with the development of fungal diseases. In order to garden trees were healthy, it is necessary to carry out prevention by spraying with solutions before flowering and after it ends.
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 happen during replanting, loosening the soil, pruning or tilling. Due to disruption of the vital functions of tree tissue, general withering occurs. It is difficult to determine the problem in this case. Restore fruit tree In the garden in the summer, either fertilizing or using biological preparations to cover wounds will help.
Unlike animals, which obtain the substances and energy necessary for life from the food they eat, ordinary plants consume three separate streams of substance/energy, namely:
- minerals and water are supplied through root system;
- carbon dioxide, necessary for the synthesis of biomass, comes from the surrounding air through the leaves;
- energy - absorbed by leaves from the stream of sunlight falling on them.
The absorption of light energy is possible only through its interaction with colored substances (plant pigments) during the process of photosynthesis. The main photosynthetic pigments in plants are chlorophylls, which give plants their green color. For photosynthesis of different groups of substances (carbohydrates, proteins), chlorophyll absorbs the blue and red components of the solar spectrum, ignoring the green one as “unnecessary” (the real process is even more complex and interesting - which is noticeable from photographs of living plants in the near-infrared spectrum).
The remaining groups of pigments (yellow xanthophylls, orange carotenes, as well as red, purple and blue anthocyanins) are present in the plant leaf in small quantities. You can see them in etiolated (grown without light and therefore without chlorophyll) plants or their parts - for example, in potato shoots germinating in the dark. The chromophore groups of chlorophyll molecules, which are responsible for absorbing parts of the light spectrum, are very “delicate”: 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 the leaves in autumn?
In preparation for the period of winter dormancy, the plant, if possible, “pumps out” all potentially useful substances from the leaf biomass 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 varied, but typically has a brown tint). Therefore, the withering leaf acquires one color shade, which is provided to it by the dyes remaining in the leaf blade, and in proportion to their quantity/concentration - and precisely because of this autumn forest painted in such varied and bright colors.
How does a plant “know” that autumn has arrived?
In a living plant, many “internal clocks” function simultaneously - processes related to the influence external factors(cyclical fluctuations in temperature, light, and so on). In relation to the leaf, the most important factor here is the relative (as a share of the entire daily cycle) and absolute (in hours) daylight hours - this is how the process of preparing the plant for winter period peace. In addition to changes in biochemical processes, in deciduous trees, the growth of cells in the cork layer is initiated at the base of the leaf, which gradually breaks the connection between the leaf and the tree - and the leaf falls.
Greetings, my dear researchers!
Today on discussion new project, the material on which may be useful to you for your next presentation in class “ The world around us" Why do leaves turn yellow in autumn? This question is often interesting for children, especially when they are walking along park path, raking fallen leaves with his foot. But really, why?
Lesson plan:
What artist paints leaves?
In the summer, the green canopy of trees lives through a process called photosynthesis. Have you heard of this one?
I think it’s no secret even for preschoolers that leaves absorb carbon and process it with the help of solar energy into organic substances that they feed on, releasing oxygen back. This magic inside a tree leaf only happens when comfortable conditions: Warmth and sunlight are important to him. What is responsible for paints?
How do pigment neighbors live in leaves?
I see the question in my eyes: “Why, if all the pigments live together, are there no yellow and orange leaves in the summer, but no green leaves in the fall?”
The thing is that active chlorophyll, with its large amount in warm time masks other dyes, they are simply not visible. With the onset of autumn, when there is little sun and daylight, the green artist begins to be produced less and less, no longer being replenished in such quantities as in the summer. That's when other shades begin to shine through.
That’s why very often, at the very beginning of autumn, the leaves on the tree are not all colored at once, but are painted in a bizarre pattern, when green veins still remain on the yellow or orange background.
Every day closer to winter, the existing chlorophyll is destroyed, new chlorophyll is not replenished due to the lack of conditions for photosynthesis. The veins of the leaves, through which nutrients flow, are closed with a dense plug of cells, reducing the amount of sap in the plant.
Here it is: golden autumn in full swing green leaves can no longer be found on the tree! Moreover, the faster the cold sets in, the sooner the tree “turns off” photosynthesis. A colorful carpet appears under your feet, it’s time to collect a colorful autumn herbarium or make a couple of crafts from autumn gifts.
Why do trees shed leaves?
Yellow leaves are circling over the city,
With a quiet rustling they fall at our feet...
Indeed, they would stand all winter long, delighting us with their bright beauty. But no! Leaves begin to fall at our feet, heralding the change of season. Why?
With the arrival of cold weather, the soil begins to freeze, and the trees no longer have enough moisture and minerals. Life processes gradually fade out, all plants go into hibernation. How can you sleep if every leaf needs to be fed? We have to save on food by getting rid of unnecessary consumers, which is why trees shed their leaves before winter.
At the place where the leaf petiole is attached, a special cork layer is formed, which blocks the flow of nutrients from the tree. The leaves hold on weaker and weaker every day and gradually fall off. As when changing color, they do not all leave the tree at once. Some will linger longer, fluttering in the wind, some will fall among the first, lining golden paths.
Therefore, leaf fall is a condition for the continuation of the life of a tree, necessary so that with the arrival of spring we can once again enjoy young green leaves.
This is how briefly we found the answer to the question posed today. To make the report interesting, I propose a puzzle on an autumn theme. Catch it! And I say goodbye to you until we meet again on projects.
“On a stream, pockmarked and motley,
Poem - “Before the Rain”
Evgenia Klimkovich.
When the days become shorter and the sun no longer generously shares its warmth with the earth, one of the most beautiful times of the year begins - autumn. She, like a mysterious sorceress, changes the world around her and fills it with rich and unusual colors. These miracles occur most noticeably with plants and shrubs. They are one of the first to respond to weather changes and the onset of autumn. They have three whole months ahead to prepare for winter and part with their main decorations - leaves. However, first, the trees will certainly delight everyone around with the play of color and the madness of colors, and the fallen leaves will carefully cover the earth with their blanket and protect its smallest inhabitants from severe frosts.
Autumn changes in trees and shrubs, the reasons for these phenomena
In autumn, one of the most important changes in the life of trees and shrubs occurs: a change in the color of foliage and leaf fall. Each of these phenomena helps them prepare for winter and survive such a harsh time of year.
For deciduous trees and shrubs, one of the main problems in winter time year is a lack of moisture, so in the fall all useful substances begin to accumulate in the roots and core, and the leaves fall off. Leaf fall helps not only to increase moisture reserves, but also to save them. The fact is that leaves evaporate liquid very strongly, which is very wasteful in winter. Coniferous trees, in turn, can afford to show off their needles even in the cold season, since the evaporation of liquid from them occurs very slowly.
Another reason for leaf fall is the high risk for branches to be broken under the pressure of a snow cap. If fluffy snow fell not only on the branches themselves, but also on their leaves, they would not be able to withstand such a heavy load.
In addition, many harmful substances accumulate in the leaves over time, which can only be gotten rid of when the leaves fall.
One of the recently uncovered mysteries is the fact that deciduous trees, placed in a warm environment, and therefore not needing preparation for cold weather, also shed their leaves. This suggests that leaf fall is not so much associated with the change of seasons and preparation for winter, but is an important part life cycle trees and shrubs.
Why do leaves change color in autumn?
With the onset of autumn, trees and shrubs decide to change the emerald color of their leaves to brighter and unusual colors. At the same time, each tree has its own set of pigments - “paints”. These changes occur because the leaves contain a special substance, chlorophyll, which converts light into nutrients and gives the foliage its green color. When a tree or shrub begins to store moisture and it no longer reaches the emerald leaves, and the sunny day becomes much shorter, chlorophyll begins to break down into other pigments, which give the autumn world crimson and golden tones.
Brightness autumn colors depends on weather conditions. If the weather is sunny and relatively warm, the autumn leaves will be bright and variegated, and if it rains often, then they will be brown or dull yellow.
How the leaves of different trees and shrubs change color in autumn
Autumn owes its riot of colors and their unearthly beauty to the fact that the foliage of all trees different combinations colors and shades. The most common color of the leaves is purplish. Maple and aspen boast a crimson color. These trees are very beautiful in autumn.
The leaves of birch become light yellow, and those of oak, ash, linden, hornbeam and hazel become brownish-yellow.
Hazel (hazel)
The poplar quickly sheds its foliage; it just begins to turn yellow and has already fallen off.
Shrubs also delight with the variety and brightness of colors. Their foliage turns yellow, purple or red. Vine leaves (grapes are shrubs) acquire a unique dark purple color.
The leaves of barberry and cherry stand out against the general background with a crimson-red hue.
Barberry
Rowan leaves can be yellow to red in autumn.
The viburnum leaves turn red along with the berries.
Euonymus dresses in purple clothes.
Red and purple shades foliage is determined by the pigment anthocyanin. An interesting fact is that it is completely absent from the leaves and can only be formed under the influence of cold. This means that the colder the days, the more crimson the surrounding leafy world will be.
However, there are plants that not only in autumn, but also in winter, retain their foliage and remain green. Thanks to such trees and shrubs, the winter landscape comes to life, and many animals and birds find their home in them. In the northern regions, such trees include pine, spruce and cedar. To the south the number of such plants is even greater. Among them are trees and shrubs: juniper, myrtle, thuja, barberry, cypress, boxwood, mountain laurel, abelia.
Evergreen tree - spruce
Some deciduous shrubs also do not part with their emerald clothing. These include cranberries and lingonberries. On Far East There is interesting plant wild rosemary, the leaves of which do not change color in the fall, but curl up into a tube in the fall and fall off.
Why do the leaves fall but there are no needles?
Leaves play an important role in the life of trees and shrubs. They help create and store nutrients and also accumulate mineral components. However, in winter, when there is an acute lack of light, and, therefore, nutrition, the leaves only increase the consumption of useful components and cause excessive evaporation of moisture.
Coniferous plants, which most often grow in areas with a rather harsh climate, are in great need of nutrition, so they do not shed their needles, which act as leaves. The needles are perfectly adapted to cold weather. The needles contain a lot of chlorophyll pigment, which converts nutrients from light. In addition, they have a small area, which significantly reduces the evaporation of much-needed moisture from their surface in winter. The needles are protected from cold weather by a special wax coating, and thanks to the substance they contain, they do not freeze even in severe frosts. The air that the needles capture creates a kind of insulating layer around the tree.
The only one coniferous plant The tree that leaves its needles for the winter is larch. It appeared in ancient times, when summers were very hot and winters incredibly frosty. This climate feature led to the fact that the larch began to shed its needles and there was no need to protect them from the cold.
Leaf fall, as a seasonal phenomenon, occurs in each plant at its own specific time. It depends on the type of tree, its age and climate conditions.
Poplar and oak are the first to part with their leaves, then the time comes for rowan. The apple tree is one of the last to shed its leaves, and even in winter, there may still be a few leaves left on it.
Poplar leaf fall begins at the end of September, and by mid-October it completely ends. Young trees retain their foliage longer and turn yellow later.
The oak begins to lose its leaves at the beginning of September and after a month it completely loses its crown. If frosts start earlier, leaf fall occurs much faster. Along with the oak leaves, acorns also begin to fall off.
Rowan begins its leaf fall in early October and continues to delight with its leaves until November 1st. pink leaves. It is believed that after the rowan leaves its last leaves, dank, chilly days begin.
The leaves on the apple tree begin to turn golden by September 20th. By the end of this month, leaf fall begins. The last leaves fall from the apple tree in the second half of October.
Evergreen plants and shrubs do not lose their foliage even with the onset of cold weather, as do ordinary deciduous trees. Permanent leaf cover allows them to survive any weather conditions and maintain the maximum supply of nutrients. Of course, such trees and shrubs renew their leaves, but this process occurs gradually and almost imperceptibly.
Evergreens do not shed all their leaves at once for several reasons. Firstly, then they do not have to spend large reserves of nutrients and energy to grow young leaves in the spring, and secondly, their constant presence ensures continuous nutrition of the trunk and roots. Most often, evergreen trees and shrubs grow in areas with a mild and warm climate, where the weather is warm even in winter, however, they are also found in harsh climatic conditions. These plants are most common in tropical rainforests.
Evergreen plants such as cypresses, spruce trees, eucalyptus trees, some types of evergreen oaks, and rhodendron can be found over a wide area from harsh Siberia to the forests of South America.
One of the most beautiful evergreens is the blue fan palm, which grows in California.
The Mediterranean oleander shrub is distinguished by its unusual appearance and height of more than 3 meters.
One more evergreen shrub is gardenia jasmine. Its homeland is China.
Autumn is one of the most beautiful and vibrant times of the year. Flashes of purple and golden leaves preparing to cover the ground with a colorful carpet, coniferous trees piercing the first snow with their thin needles and evergreens, always pleasing to the eye, make the autumn world even more delightful and unforgettable. Nature is gradually preparing for winter and does not even suspect how fascinating these preparations are to the eye.
Valentina lame
Summary of the GCD “Why do the leaves turn yellow?” in the preparatory group
Goals:
1. Teach children to correlate the description of nature in poetry with a certain time year:
Develop auditory attention and quick thinking.
2. Give children knowledge about Why with the onset of autumn leaves on trees turn yellow; ideas about the beginning of autumn, about the dependence of color brightness leaves from the weather.
3. Develop children’s ideas about the signs of autumn, concepts: bush, tree.
4. Practice writing descriptive stories about trees and the ability to determine the name of a tree from the description.
Activating the dictionary: chlorophyll, crimson, bush.
5. Foster a desire to study nature and protect it.
Material: boxes with fruits and leaves trees of the Tula region, familiar to children, book by Georgy Graubin « Why leaves fall in autumn» .
Children, I will read you excerpts from poems, and you listen to them carefully and tell me what time of year we are talking about. AND Why? (reading):
“In the morning we go to the yard
Leaves are falling like rain,
They rustle underfoot
And they fly, fly, fly..."
“I bring the harvest. I am sowing the fields again,
I send the birds south, I strip the trees,
But I don’t touch the pines and fir trees
I...autumn. (children's answers)
Children, how do you determine that autumn has come? (children's answers). That's right, birds fly away warm regions, the day is slowly waning, insects are disappearing, leaves turn yellow and fall off, harvest is being harvested in fields, orchards and orchards. - When does autumn come? (children's answers)
According to the calendar, autumn begins on September 1, when the first autumn month begins and schoolchildren go to school. Astronomers consider the beginning of autumn to be the day of the autumnal equinox, September 23, when the day is equal in length to the night. The beginning of autumn in wildlife is considered to be the appearance yellow leaves on a birch.
And you know why do the leaves turn yellow? Would you like to know this secret? (children's answers) Then listen. (I’m reading a story from G. Graubin’s book « Why do leaves fall in autumn?» « Why do the leaves turn yellow?» .
Autumn. It's still a long way from frost, but the trees are already starting to fall foliage. Trees are not immediately freed from leaves. Coming preparing for leaf fall. IN leaves amazing transformations take place.
In the beginning leaves begin to turn yellow, although no one adds color to juices. Yellow dye is always in the leaves. Only in summer yellow invisible. It is clogged with a stronger color - green. Green leaves a special substance - chlorophyll - will come. What is the name of the green substance? (children's answers) Chlorophyll in leaves gradually destroyed and restored again under the influence of the sun. In summer the sun shines for a long time and chlorophyll is restored very quickly and the leaf is always green. But autumn comes, the nights become longer, the plants receive less light. Chlorophyll is destroyed and does not have time to recover. Green color decreases in foliage and becomes noticeable yellow: the leaf turns yellow. Why does the leaf turn yellow?? (children's answers)
But in the fall leaves become not only yellow, and also red, crimson, purple. It depends on what coloring matter is in withering sheet.
The autumn forest is rich in its colors. The brightness of autumn leaves depends on what the weather is like.
If autumn is long and rainy - coloring leaves from excess water and lack of light it will be dull and inexpressive.
If cold nights alternate with clear days, then the colors will be rich and bright.
But the alder and lilac the leaves will fall green, regardless of the weather. In their leaves except chlorophyll, there are no other substances.
Here's the secret you learned about coloring leaves on trees.
Now we'll have a little rest and play.
Physical education minute.
Now, tell me, what is the difference between a tree and a bush? (children's answers). Correctly, a tree has one thick trunk and many branches, while a bush has several thin trunks.
I suggest you compete “Who can name more trees?” (children answer and receive a chip for the correct answer). Now, name the bushes. (children also receive chips). Well done, everyone tried to help their team.
I offer you one more game. I have them in boxes leaves and fruits different trees. You choose any box for yourself and will have to describe the tree without naming it. The one who correctly describes the tree and who is the first to recognize it will receive one chip. (game being played).
Now, count the chips and determine for yourself which team was more active today and won.
What did we learn about in class today? That's right, we found out: why do the leaves turn yellow when autumn comes, what determines the brightness of the color leaves, remembered how trees differ from shrubs and described them very well. Were you interested? I'll tell you in the next lesson why and how leaves fall.