Why leaves change color in autumn summary. What substance colors foliage green, yellow, orange, red: plant pigments. Why do leaves change color in autumn? Which tree group leaves turn red in autumn? Experiment for children

When the days become shorter, and the sun no longer generously shares its warmth with the earth, one of the most beautiful seasons of the year comes - autumn. She, like a mysterious sorceress, changes the world around and fills it with juicy and unusual colors. Most notably, these miracles occur with plants and shrubs. They are among the first to respond to weather changes and the onset of autumn. They have three whole months ahead of them to prepare for winter and part with their main decorations - leaves. However, at first, the trees will certainly please everyone around with their play of colors and the frenzy of colors, and the fallen leaves will carefully cover the earth with their veil and protect its smallest inhabitants from severe frosts.

Autumn changes with trees and shrubs, the causes of these phenomena

In autumn, one of the most important changes in the life of trees and shrubs occurs: a change in the color of the foliage and leaf fall. Each of these phenomena helps them prepare for winter and survive such a harsh season.

For deciduous trees and shrubs, one of the main problems in winter time year is a lack of moisture, so in the fall everything useful material 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 the leaves evaporate the liquid very strongly, which is very wasteful in winter. Coniferous trees, in turn, can afford to show off with needles in the cold season, since the evaporation of liquid from them is very slow.

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 withstand such a heavy burden.

In addition, many harmful substances accumulate in the leaves over time, which can only be eliminated during leaf fall.

One of the recently uncovered mysteries is the fact that deciduous trees, placed in a warm environment, and, therefore, not in need of preparation for cold weather, also shed their leaves. This suggests that leaf fall is associated not so much with the change of seasons and preparation for winter, but is an important part of 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 more unusual colors. At the same time, each tree has its own set of pigments - "paints". These changes are due to the fact that the leaves contain a special substance, chlorophyll, which turns light into nutrients and gives the foliage 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.

The brightness of autumn colors depends on the weather conditions. If the street is sunny and relatively warm weather, then the autumn leaves will be bright and variegated, and if it rains often, then brown or dull yellow.

How the leaves of different trees and shrubs change color in autumn

The riot of colors and their unearthly beauty autumn owes to the fact that the foliage of all trees different combinations colors and shades. The most common purple color of the leaves. Maple and aspen can boast of crimson color. These trees are very beautiful in autumn.

Birch leaves become light yellow, and oak, ash, linden, hornbeam and hazel - brownish yellow.

Hazel (hazel)

Poplar quickly sheds its foliage, it is just beginning to gain yellowness and has already fallen.

Shrubs also delight with the variety and brightness of colors. Their foliage turns yellow, purple or red. Grape leaves(grape - shrub) acquire a unique dark purple color.

The leaves of barberry and cherry stand out against the general background with a crimson-red tint.

Barberry

From yellow to red, rowan leaves can be in autumn.

The leaves of the viburnum turn red along with the berries.

Euonymus dresses in purple clothes.

Red and purple shades of foliage determines the pigment anthocyanin. An interesting fact is that it is completely absent in the composition of 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 trees: pine, spruce and cedar. To the south, the number of such plants is even greater. Among them, trees and shrubs are distinguished: juniper, myrtle, thuja, barberry, cypress, boxwood, mountain laurel, abelia.

Evergreen tree - spruce

Some deciduous shrubs also do not part with their emerald clothes. These include cranberries and cranberries. On the Far East there is interesting plant wild rosemary, the leaves of which do not change color in autumn, but roll up into a tube in autumn and fall off.

Why do the leaves fall, but there are no needles?

The leaves are playing big role in the life of trees and shrubs. They help create and store nutrients, as well as accumulate mineral components. However, in winter, when there is an acute shortage 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 that act as leaves. The needles are perfectly adapted to the cold. The needles contain a lot of chlorophyll pigment, which converts nutrients from light. In addition, they have a small area, which significantly reduces evaporation from their surface so necessary winter moisture. From the cold, the needles are protected by a special wax coating, and thanks to the substance they contain, they do not freeze even in very coldy. The air that the needles capture creates a kind of insulating layer around the tree.

the only coniferous plant, which parted for the winter with its needles is larch. She appeared in ancient times when summers were very hot and winters incredibly cold. This feature of the climate led to the fact that the larch began to shed its needles and it was not necessary to protect them from the cold.

Leaf fall, as a seasonal phenomenon, occurs for each plant at its own specific time. It depends on the type of tree, its age and climate.

First of all, poplar and oak part with their leaves, then the time of mountain ash comes. The apple tree is one of the last to shed its leaves, and even in winter, it may still have a few leaves.

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.

Oak begins to lose its leaves in early September and completely loses its crown in a month. If frosts begin earlier, then leaf fall occurs much faster. Along with oak leaves, acorns also begin to crumble.

Mountain ash begins its leaf fall in early October and continues to delight with its pink leaves until November 1. It is believed that after the mountain ash parted with the last leaves, dank chilly days begin.

The leaves on the apple tree begin to turn golden by September 20. By the end of this month, leaf fall begins. The last leaves fall from the apple tree in the second half of October.

Evergreens and shrubs do not lose their foliage even with the onset of cold weather, as ordinary hardwoods do. Permanent leaf cover allows them to survive any weather and preserve 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 uninterrupted 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.

Evergreens such as cypresses, spruces, eucalyptus, some types of evergreen oaks, rhodendron can be found in a wide area from harsh Siberia to the forests of South America.

One of the most beautiful evergreens is the blue fan palm, which is native to California.

The Mediterranean oleander shrub is distinguished by an unusual appearance and a height of more than 3 meters.

Another evergreen shrub is gardenia jasmine. Her homeland is China.

Autumn is one of the most beautiful and colorful seasons. Flashes of purple and gold leaves, preparing to cover the ground with a multi-colored carpet, coniferous trees, penetrating 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.

Baykeev Artur

Study of the causes of leaf fall, preparation of trees for winter, conclusions obtained as a result of observations. This work took second place at the regional scientific and practical conference

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Slide #2

Sad time! oh charm!
Your farewell beauty is pleasant to me -
I love the magnificent nature of wilting,
Forests clad in crimson and gold...
F. I. Tyutchev

Autumn is a wonderful time of the year.

Slide #3

Leaf color change is one of the first signs of autumn. I've always been interested to know where autumn has so many bright colors, because in the summer all the leaves are green, where do the emerald overflows of summer disappear, why in the fall the leaves begin to change their color. In autumn I like to be in nature: to wander, to breathe fresh air, observe nature, collect bouquets from fallen leaves.

Slide number 4.

Why do leaves fall off trees so easily in autumn? Yesterday I couldn't even break them strong wind and now they fall off on their own. What happened? Will leaf fall damage the tree itself? I decided to do research and solve this mystery.

Slide #5

I suggested that the leaves change color due to a decrease in air temperature, and a multi-colored dye appears in the leaf, and leaf fall is the preparation of deciduous trees for winter cold.

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The object of my research was trees and their leaves.

The subject of the study is the processes that occur inside the leaf in autumn.

Slide number 7.

The purpose of my research is to find out what affects the change in leaf color in the fall, why different colors in the leaves and why they fall off.

To achieve the goals set, the following tasks were defined:

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1. Conduct observations for different trees autumn;

2. Study the structure of the leaf;

3. Find out why the leaves are green in summer and change color in autumn;

4. Examine the structure of the yellow leaf by examining it through a microscope;

5. To study the literature explaining the reasons for changing the color of the leaves;

6. To study the causes of leaf fall;

I chose research methods:

Slide #9

1.Reading scientific literature, encyclopedias;

2. Use of Internet materials;

3. Conversations with adults and biology teachers;

4. Observations, experiments.

We know why there is a change of day and night, seasons. But why the change in color of the leaves occurs in the fall, we still do not know, so I made an observation of various trees in the fall.

The object of observation was the trees growing in the territory high school No. 3 and near my house on Miroshnichenko street. Acacia, birch, mountain ash, lilac, apple tree, apricot grow here.

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The first purpose of observation is to find out the timing of the change in leaf color on these trees. Having written everything down in a table, I concluded: the timing of the change in the color of the leaves of the trees is different:

1. The very first leaves of birch and apricot began to turn yellow. And the rowan leaves began to turn red. The leaves of the apple tree turned brown.

2. Lilac leaves do not change color.

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What influenced the color of the leaf? I decided to study how the leaf is arranged, to examine it under a microscope. I decided that the structure of the leaf would bring me closer to discovering the secret of leaf color.

The sheet consists of two parts:leaf blade and petiole. On the leaf blade, the veins are very clearly visible, especially from the underside. The veins are the vessels through which water and nutrients move.

To examine the pigment composition of the leaf, I chose a birch leaf. I love this tree very much and it is a symbol of our Motherland.

Purpose: to examine a birch leaf and determine what color pigment is in more, compare green leaf with autumn leaf.

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I discovered that each leaf is full of some grains. Moreover, in the green leaf there were only green grains, and in the yellow - both green and yellow. And there are much more yellow grains in the autumn leaf than green ones.

What are these grains? Why do they need a sheet? Much was unclear. And I decided to turn to scientific sources for help. Here's what I learned from the encyclopedia.

Slide #13

Each leaf is full of wonderful grains. This is chlorophyll. These grains prepare food for the tree. Chlorophyll is like a tiny kitchen inside every leaf! It helps turn sunlight and water into food for the plant. Science has proven that without a green leaf not only a plant cannot live, but there would be no life on Earth at all. It turned out that in leaf cells, with the help of chlorophyll, the most important transformations of water and carbon dioxide into sugar and starch. At the same time, the leaves release oxygen, which all living things breathe.

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The famous Russian scientist K.A. Timiryazev called the green leaf the great factory of life. Will fall on a green leaf Sunbeam- and the "factory" begins the transformation of water and carbon dioxide into starch and sugar. There is no light - and the work in the grains of chlorophyll freezes. Leaves are green in summer due to a large number chlorophyll.

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However, along with chlorophyll, green leaves contain other pigments - yellow xanthophyll and orange carotene. In summer, these pigments are invisible, as they are masked by chlorophyll. In autumn, chlorophyll is destroyed. This is where the yellow and red shades of xanthophyll and carotene appear in the leaf.

The destruction of chlorophyll occurs more strongly in the light, that is, in sunny weather. That is why in cloudy rainy autumn the leaves retain their green color longer. But if "Indian summer" comes to replace the rains, then the trees turn into golden colors of autumn in 1-2 days. In addition to gold, the autumn dresses of trees contain crimson hues. This color comes from a pigment called anthocyanin.

Conclusion:

autumn due to lower temperatures, a decrease in the number sunlight chlorophyll is destroyed and yellow and red shades of xanthophyll, carotene, anthocyanin appear in the leaf. Leaves don't change color, they just lose their green color My hypothesis that the change in leaf color is associated with a decrease in temperature is partially confirmed, and the assumption that substances of red, yellow and other colors appear in the leaf in autumn turned out to be erroneous: no multi-colored substances appear in the leaf, the leaves do not change their color they just lose their green color.

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Why are the leaves falling? How does leaf fall happen? Does the tree need it? These are mysteries that I wanted to unravel.

I watched the branches from which the leaves fell off. Does the wound remain in the place where the leaf hung? Found out - no, in that place only a kidney. Moreover, this kidney is tightly closed and covered with brown scales on top. So, as the days became shorter, the amount of sunlight decreased, the trees gradually prepared for winter: they formed buds, scales. For what? From the encyclopedia and from conversations with biology teachers, here's what I learned about preparing trees for leaf fall.

The amount of sap in the tree is decreasing. Chlorophyll disappears. accumulate in the leaves harmful substances(metabolism). The leaves are getting old. The vessels through which water enters the sheet are blocked at the base with cork cloth and a separating layer is formed. A breath of breeze is enough - and the leaf comes off.

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Conclusion: leaf fall occurs according to a certain algorithm: chlorophyll is destroyed in the leaves, the leaf accumulates unnecessary substances, the leaf changes color, the leaf becomes brown, the leaf comes off, the leaf falls.

I found the answer to the question of how a leaf separates from a tree branch in autumn, I learned that leaf fall is a natural stage in the life of a plant. The signal for the beginning of leaf fall is not a drop in temperature, but a change in duration. daylight hours- the surest and unchanging sign of the onset of autumn.

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Nature made sure that the parting of a tree with a leaf was painless for him. Preparation for leaf fall begins in advance. At the end of summer, a separating (cork) layer is formed. The leaf remains hanging on the tree only thanks to the vascular bundles. Vascular bundles are easy to see on the sheets in the form of large dots. A small impact, for example, a gust of wind, is enough to break this last connection between the petiole of the leaf and mother plant. Leaves can also fall in completely calm weather under the influence of the gravity of the leaf blade. In place of the scar from the torn off sheet, a protective cork layer is formed.

Why do trees shed their leaves in autumn?I believe that this helps the trees to save themselves from the accumulation of snow between the branches, from the breakage of the branches. The snow slips past the branches onto the ground. And the trees, probably, “fall asleep” for the winter, in order to more easily endure frosts.

And here is what I learned on this subject from the encyclopedia.

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In summer, the tree takes water from the soil and evaporates a lot of water. But with cooling, the flow of water from the soil is greatly reduced; in winter, it is very difficult to extract moisture from frozen soil. Trees with leaves in winter would die from lack of moisture, that is, they would dry up.

Dropping leaves in autumn, trees protect themselves from mechanical damage under the pressure of snow.

During leaf fall, the tree gets rid of excess mineral salts, which are sucked in by the roots from the soil. Part of the salts is used by the plant for nutrition, and the rest of the salts are deposited in the cells of the leaves. The more moisture the leaf evaporates, the more salts it contains by autumn. An excess of mineral salts disrupts the normal functioning of the leaves. Therefore, shedding old leaves is necessary condition to keep the plant alive.

Conclusion: leaf fall allows the plant to save water, the plant uses the leaves as a container to remove unnecessary substances, it prevents branches from breaking off in winter under the weight of snow.

People have been observing nature for a long time. The people have signs associated with a change in the color of the leaves

Although the leaf has turned yellow, it falls off weakly - frosts will not come soon.

If in autumn the birch leaves begin to turn yellow from the top, then the next spring will be early, and if from below, then late.

Untimely, yellow leaves will appear on the trees - by early autumn.

Thus, with a detailed study of the literature, a thorough examination appearance leaves, carefully observing a leaf under a microscope, observing trees, I came to the following conclusion:

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1. Leaves do not change their color, they just lose their green color in autumn. The color of the autumn leaf depends on what coloring matter is in the withering leaf.

My hypothesis that the color of the leaf changes only due to a decrease in air temperature turned out to be not entirely correct. Plants need sunlight. And in autumn time its getting smaller every day. The color of the leaves also depends on the amount of sunlight.

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And the hypothesis put forward by me that leaf fall is an adaptation of deciduous trees and shrubs to the winter cold is confirmed. The tree needs to reduce the amount of evaporated moisture, save itself from mechanical damage in the winter. And during leaf fall, the tree gets rid of excess mineral salts. Dropping old leaves is a necessary condition for the plant.

Slide number 22.

The collected information will help in the future when studying the world around us, biology, chemistry, expanded my horizons. I learned and discovered a lot of interesting things and I will share these discoveries with friends and classmates.

Slide #23

I express my gratitude to my parents, head teacher primary school MBOU Secondary School No. 3 Galda Tatyana Nikolaevna for help in preparing and writing a research paper.

Morozova Victoria
Research activity "Why do leaves turn yellow and fall off in autumn?"

Subject: « Why do leaves turn yellow and fall off in autumn??»

Relevance.

Plunging into everyday problems, adults stop paying attention to the world, while children are surprised by its seasonal changes daily.

Target research: To introduce children to the structure tree leaf and learn, why leaves the trees change color and fall off.

Thing research: Change tree leaves in autumn.

An object research: autumn tree leaves.

Hypothesis research: leaves trees will change their color and fall off at the right time, because trees live their changing lives from season to season.

Target: Conduct an experiment with children that can confirm or refute our assumption. Is it possible to save the leaves on the trees so they don't change color.

Tasks research:

1. Expand children's knowledge about the life of trees in different time of the year.

2. Study the structure with children sheet, using a magnifier and a microscope. Find out what is important leaves in the life of a tree.

2. Find out Why do leaves change color and fall off in autumn?.

3. Conduct an experiment "The Greens leaflets» .

4. Check out the results research.

Methods research:

Experiment;

Observation;

With the children of our group were held conversations: about the life of trees at different times of the year, about the signs of the season « autumn» and etc.

Parents were surveyed for topic: « Why do some leaves on trees turn yellow?, others blush, and still others turn brown altogether. The answer turned out to be quite simple. The fact is that in addition to chlorophyll leaves plants contain other pigments, but because of the predominant green, they are simply not visible. As the green chlorophyll recedes, other colors become visible.

Using a magnifying glass and a microscope, we studied the structure sheet. We first considered the petiole - this is the part that connects leaf with branch, then the top surface sheet. We examined the veins - thin tubes that go from the petiole around sheet. Top surface sheet absorbs sunlight and is therefore always darker than the underside sheet. edge sheet is called"edge". Considered edge sheet, the tip is sharp or rounded.

Using a piece of white cloth, we conducted an experiment under name: « Why is the leaf green?» . Have taken leaflet and put it inside a piece of white cloth folded in half. Then a wooden cube was strongly knocked on leaflet through fabric. What did we discover during the experiment? Green spots appeared on the fabric. This green substance leaflet, is called chlorophyll, and it turns it green. When it comes autumn and it gets colder and less sunlight. This green substance gradually decreases until disappears completely. Then, leaf turns yellow, brown or red.

Subsequently, we made drawings leaves, which contain right amount chlorophyll, sketches of the structure sheet. This was a confirmation of one of the points of our hypothesis of the experiment.

Via table lamp, we have carried out an experiment name: "The Greens leaflets» which lasted several days. With it, we observed the ongoing changes in color leaves.

How did leaves:

yellow leaves get their color as a result "work" plant pigment xanthophyll;

orange the leaves put on their autumn outfit when the pigment carotene becomes visible, which, by the way, is familiar to everyone by the bright orange color of carrots;

Red leaves acquire this unexpected color due to anthocyanin pigments;

Brown leaves- this is no longer the color of pigments, but the color of cell walls sheet, it appears when other visible coloring pigments are absent.

Conclusion: Conducted by us study and studied materials on the topic, became a confirmation of the theory of the irreversibility of time or "Law of nature". Since the conditions we created and the experience we had made did not help to save green leaves on tree branches.

Synopsis of NNOD on ecology in the preparatory school group “Why do the leaves turn yellow and fall off?”