What gives the leaves their yellow color. Why do some leaves turn red and yellow in the fall, while others remain green? Video: Why leaves change color

Yellow and red, orange and brown - all leaves have their own shade. Let's figure out where this difference in color comes from.

In summer the leaves are green due to large quantity chlorophyll. This pigment is the plant’s breadwinner, since it is with its help that the plant synthesizes glucose from carbon dioxide and water in the light, and from it all other nutrients. In the presence of light, chlorophyll in a living leaf is constantly destroyed and re-formed.

In addition to chlorophyll, the leaves also contain other dyes - yellow xanthophyll and orange carotene (the same one found in carrots). In summer, these pigments are invisible, as they are masked by a large amount of chlorophyll. In autumn, vital activity in the leaf dies out, and chlorophyll is gradually destroyed. This is where the yellow and orange hues come into play.

The destruction of chlorophyll occurs more intensely in sunny weather. This is why in cloudy, rainy autumn the leaves retain their green color longer. But if the precipitation is replaced by Indian summer, then the crowns of the trees turn into the usual autumn colors in a couple of days.

Besides the golden ones, many crimson leaves fall at our feet. They are like this because of a pigment called anthocyanin. Unlike chlorophyll, anthocyanin is not associated with intracellular plastic formations (grains), but is dissolved in cell sap.

When the temperature decreases, as well as in bright light, the concentration of anthocyanin in the cell sap increases. In addition, stopping or delaying the synthesis of nutrients in the foliage also stimulates its synthesis. Thus, the red color of leaf fall simply indicates that the life processes in the leaves are stopping in anticipation of winter.

The brightness of autumn colors depends on what the weather is like. If there is a lot of rain, the foliage will be dull and inexpressive due to excess water and lack of light. If cold nights alternate with clear ones on sunny days, then the colors will match the weather - rich and bright. The leaves on the south side of the tree will also always be more saturated in color, as they receive more sunlight.

Yesterday, while walking in the park, for some reason I thought for the first time. Why are the leaves multi-colored and this is what I found on the internet: The leaves of plants are colored green because they contain chlorophyll, a pigment that is present in plant cells. A pigment is any substance that absorbs visible light. Chlorophyll absorbs sunlight and uses its energy to synthesize nutrients.

But in autumn, plant leaves lose their bright green color.

For example, poplar leaves turn golden, while maple leaves seem to flash red. Some chemical transformations begin in the leaves, that is, something happens to chlorophyll. With the arrival of autumn, plants prepare for winter. Nutrients slowly move from the leaves to the branches, trunk, root and are stored there during the severe cold. As spring arrives, plants use their stored energy to grow new green leaves.

When the energy of the stored nutrients is exhausted, the synthesis of chlorophyll stops. The chlorophyll remaining in the leaves partially decomposes, and pigments of a different color are formed. Yellow and orange pigments appear in the leaves of some plants. These pigments consist for the most part from carotenes - substances that color carrots orange. For example, the leaves of birch and hazel become bright yellow as chlorophyll decays, the leaves of some other trees acquire various shades of red.

The red, dark cherry and purple hues of some leaves are due to the formation of anthocyanin pigment. This pigment colors radishes, red cabbage, roses and geraniums. Under the influence of autumn cold, chemical reactions begin in the leaves, turning chlorophyll into red-yellow compounds. Unlike carotenes and other yellow pigments, anthocyanin is generally absent from green leaves. It is formed in them only under the influence of cold. Color autumn leaves, like human hair color, is determined genetically in each plant species. But whether this color will be dull or bright depends on the weather.

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). In autumn, when the leaves are isolated from the branches of the tree and water and minerals, photosynthesis stops. When the leaves are isolated, the nutrition-producing chlorophyll that gives the leaves their green color is destroyed, and other colors begin to appear - they were present in the leaves all along, but due to the abundance of green chlorophyll, they were not visible. Yellow and orange colors appear - this is a tribute to the pigment carotene, thanks to which, by the way, carrots have their orange color.

The beautiful colors of autumn are also the work of pigments that are formed as a result chemical reactions caused by a unique combination of weather conditions in the fall: cooler temperatures at night and more short days promote the formation of anthrocyanin, a pigment that gives leaves red and purple shades. Autumn temperatures produce red colors that result from a reaction with glucose, the sugar left in the leaves after photosynthesis has stopped.

The brightness of the colors of autumn leaves and the time during which we can admire them before the leaves fall depend on changes in the weather. At low temperatures(but not reaching freezing point), more anthrocyanin is produced, which gives the leaves a bright red color. The brighter colors of autumn can also be a result of gloomy and rainy days.

Every year in mid-autumn we all observe a beautiful color spectacle of falling leaves, but hardly anyone thinks about why this happens and what it is connected with. Leaves that turn rusty in autumn can be said to be a food plant nature. Plants obtain water from the soil through their roots and their leaves absorb carbon dioxide from the air. By using sunlight water and carbon dioxide are converted into glucose. It stimulates the growth and development of greenery.

The process of converting water into glucose using sunlight is called photosynthesis. Contributing to this process is Chemical substance called chlorophyll. It is what gives plants their green color.

By the end of summer - beginning of autumn, the days become shorter. Thus, the trees sense the approaching cold and begin to prepare for winter.

In cool weather, the amount of water and sunlight is insufficient to facilitate photosynthesis. At this time, the trees begin to feed on the food they accumulated during the summer. The so-called green plant is closed, a lack of chlorophyll is gradually causing the leaves to lose color and take on the rusty hue of autumn. Depending on the temperature and humidity of the weather, the leaves will lose their green color faster, and if there is a sudden early frost, they will fall off faster.

Maple leaves, for example, retain significant amounts of glucose in their composition, even after photosynthesis has completed. Thus, cold nights and those few rays of sun that manage to deceive the clouds and nourish the leaves are the main ingredient in trees whose leaves are colored bright red.

Oak leaves appear in autumn Brown color, since they store not only glucose, but also waste.
Trees and plants prepare for winter, and give us the opportunity to admire their beautiful colors every time.

Chlorophyll is a real food production unit that is found in every leaf. Two-thirds of the leaves depend on the presence of chlorophyll. Each leaf has other shades, but due to the dominant one, they are almost invisible. But they still exist. "Xanthophyll" - has a yellow color. It consists of oxygen, hydrogen and carbon and occupies 23% of the pigmentation of the entire leaf. Another shade is given by carotene and it accounts for 10% of the total pigmentation.

Anthocyanin gives leaves bright red shades. From early spring until autumn, only green chlorophyll is visible to us. But when autumn begins, nutrients enter only the trunk and branches of trees, because nutrients cease to be produced, and the existing chlorophyll decomposes. When it completely disappears or its content in the foliage decreases significantly, this is where other pigments that are constantly present in the leaf appear. That's when the variety of colors on the trees begins.

Before a leaf falls from a tree, a thin layer cells, which indicates the location of this leaf.

But today there is another theory about trees shedding their leaves as winter approaches. It was put forward by British scientist Brian Ford. The theory was proposed for discussion in The Daily Telegraph. He believes that trees shed their leaves for the same reason that a person does when going to the toilet. Wanting to get rid of excess substances accumulated inside, the tree gets rid of its foliage. So for a long time the leaf was perceived as an energy storage organ, but the same leaf also removes all unwanted substances from the tree. Before shedding, the level of harmful components of tannin, oxolate, and heavy metals in the leaves increases. Hence the conclusion follows that the tree rather wants to free itself from harmful substances rather than storing it for the winter. The proposed hypothesis cannot prevent you from admiring the autumn colors.

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The world is beautiful in its diversity. There are a lot of plants and trees on the planet. When we think about nature, we imagine a walk through a deciduous forest or clearing. In summer, the natural spaces are surrounded by greenery. And in the fall, the trees take on a solemn appearance, donning multi-colored outfits. Let's try to figure out why the leaves turn yellow?

Every green leaf, even the smallest one, contains a pigment - a substance that absorbs light and forms the color of the plant and is responsible for its color. This substance is called chlorophyll. Thanks to it, a blade of grass or a leaf breathes, develops, and grows.

When trees and shrubs begin to prepare for winter, necessary substances move to the roots and core of the trunk. They will feed the living organism until spring. After all, food supplies are cold period are needed not only by animals, but also by plants. The remaining energy will be used to produce new shoots.

When beneficial elements leave the leaves, chlorophyll production stops. Its remains disintegrate, forming pigments of other colors. One of them is carotene - carrots are rich in it, so it orange color. And another pigment is responsible for the purple, red color - anthocyanin. As in a radish or a scarlet rose. So the leaves acquire different shades of yellow, orange and red. It all depends on which substance is more.

Why do trees shed their leaves?

The leaf is connected to the tree by a stalk, in which there is a cluster of small vessels. Water flows through them and useful material. But by winter, trees need to save water. And the leaves no longer serve any practical function. Therefore, in order to save water, bushes and trees get rid of their leaves and they fall off. And we enjoy the beauty of the golden autumn, so that in the spring we can again enjoy the blossoming buds.

Deinekina Ekaterina

Research on the topic "Why are the leaves green in summer and yellow and red in autumn"

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“Why are the leaves green in the summer, but the leaves on the trees are colorful in the fall?”

“The forest is like a painted tower,

Purple, gold, crimson..."

I. Bunin

1. Why are the leaves of plants green in summer?

Of the 25 people surveyed, they answered this question:

“I don’t know” - 8 people;

“enough light, heat and water” - 16 people.

2. Why do the leaves change color with the onset of autumn?

“I don’t know” - 12 people;

“from old age” - 7 people;

“from the cold” - 6 people.

As you can see, the answers are different. So I decided to put forward my hypothesis:the leaves of plants are of different colors, because they contain substances that give the leaves shades of green, yellow and red.

Target research find out:

* What substances are added to the leaves? different colors?

* Why do the leaves on the trees turn shades of yellow and red in autumn?

To achieve this goal, I set the following tasks :

1. Find out what a tree leaf is made of
2. Find out why the leaves are green in summer?
3. What substances give leaves yellow and red colors?

In order to deal with these issues, in my work I used the following methods:

1. studied the literature on this topic
2. looked up information on the Internet
3. conducted a scientific experiment

1. I built my work according to the following plan:

1. Collected and studied information about external and internal structure leaf.
2. Conducted a scientific experiment that proves the presence of coloring pigments.

What does the leaf consist of?

A leaf is one of the main organs of plants. It has a flat shape. A leaf may consist of a leaf blade, a petiole, stipules and a base with which it is attached to the stem.

The internal structure of the leaf can be seen under a microscope. The outside of the leaf is covered with skin. Under the skin is the leaf pulp, which consists of two types of tissue: columnar tissue and spongy tissue. Plants appear green to us from a large number of tiny chlorophyll grains, located mainly in the cells of the columnar tissue of the leaves. They are better lit, they form the most organic substances in the light. Through loose spongy tissue, gas exchange occurs and water evaporates. Chlorophyll grain does not remain unchanged in the plant. It doesn't last long. Capturing solar energy, chlorophyll is destroyed under the influence of light and re-created in the plant, and its formation can also occur only under the condition of good lighting.

In order to prove the presence of chlorophyll in the leaves, we conducted an experiment.

Experience 1.

We placed a green leaf in a test tube with strong alcohol. Before our eyes, the leaf begins to turn pale, while alcohol, on the contrary, quickly turns green. This process of leaf discoloration is caused by the chlorophyll dissolving in the alcohol and especially rapidly when the alcohol is heated or even gently boiled in a water bath.

Conclusion: the leaf became pale, and the alcohol solution turned green color. Consequently, chlorophyll grains give the leaf a green color, but under the influence of adverse conditions, chlorophyll grains are destroyed, and other substances give the leaf shades of yellow and red.

To make sure that the leaf contains yellow substances, let's continue the experiment.

Along with chlorophyll, yellow pigments also pass into alcohol; to separate them, we poured a little gasoline into the hood. After shaking this mixture, after a while you can notice that gasoline floats to the top, while the layer of alcohol remains at the bottom. In this case, the alcohol will have an emerald color; gasoline will take on a golden yellow color from the yellow pigments of the leaf remaining in it - xanthophyll and carotene. The separation of chlorophyll from yellow pigments is based on its greater solubility in gasoline than in alcohol.

So, I was convinced that chlorophyll is not the only coloring substance in plant tissues. From the encyclopedia, I learned that along with it, special pigments known as xanthophyll and carotene are constantly present. The first of them has a pure yellow color, the second has an orange tint. Carotene is responsible for the characteristic color of carrot roots, where it is found in very large quantities.Yellow pigments are always present in the greenery of the plant, but in summer they are completely invisible, as they are masked by the intense green color of chlorophyll.

Autumn leaf color is especially attractive with its crimson tones. However, these tones are not found in all trees. The crowns of maples and aspens are hidden in crimson; the foliage of the euonymus takes on an elegant, pinkish color; Garlands of wild grapes turn dark purple. Along with this, lindens, oaks and birches are devoid of red shades; they cast only various yellow and golden tones. What causes the red color of autumn leaves?It is caused by a special coloring substance, anthocyanin, which is extremely widespread in plants.Unlike chlorophyll, anthocyanin is not associated with plastic formations inside the cell. It is dissolved in cell sap and is less commonly found in the form of small crystals. To verify this, we conducted a second experiment.

Experience 2.

Anthocyanin is very easy to extract from any red or blue parts of the plant. To do this, we boiled a certain amount of beets and saw that the water was colored purple or dirty red by anthocyanin.

Conclusion : The leaves contain a coloring substance - anthocyanin.

I also learned that a group of scientists from the University of North Carolina at Charlotte found new patterns in the appearance of red and yellow leaves in the fall.

The research was led by Emily Habink, who examined different tree species in different areas.

It turned out that red leaves usually appear on trees that grow in poor soil, and yellow leaves on trees that grow in rich soil. It was also found that red leaves make it possible to more efficiently use the nutrients they contain in conditions of their deficiency.

Thus, as a result of a study of red maple and amberwood, she discovered that in elevated areas where the soil is poorer, these trees have much redder leaves than representatives of the same species in fertile flood areas. Therefore, the findings support the theory that the production of substances that color the leaves red helps the leaves last as long as possible and allows the tree to more efficiently stock up on nutrients for the winter.

As a result of my research, I found out:

1. The leaves contain coloring substances: chlorophyll, carotene, xanthophyll, anthocyanin.

2. Yellow pigments There are always plants in the greenery, but in summer they are completely invisible, as they are masked by the intense color of chlorophyll.

3.Under unfavorable conditions, chlorophyll is destroyed and the leaves turn red or yellow. These substances take up more and more space in the leaf in the fall, because for their formation it is necessary for it to become cooler and for the life of the plant to freeze. Also, according to scientists, the yellow or red color of the leaves depends on the composition of the soil in which they grow,Red leaves usually appear on trees that grow in poor soil, while yellow leaves usually appear on trees that grow in rich soil..

4. So As a result of my research, I found out that none of my classmates could give an accurate answer to the questions I posed. Having studied the material on this topic, I was convinced that the hypothesis I had put forward was confirmed, and now I can tell my friends what the color of the leaves depends on.

Literature:

1. David Burney “The Great Illustrated Encyclopedia of Wildlife”

1. Zapartovich B.B., Krivoruchko E.N., Solovyova L.I.

With love for nature. Didactic material in natural history for primary school. "Pedagogy", 1978.

2. Ponamareva I.I., Kornilova O.A., Kuchmenko V.S.

Biology. Plants. Bacteria. Mushrooms. "Venta Count", 1999.

Autumn is a bright period in nature, when the forest changes the color of its leaves from green to yellow, red and brown in a matter of days.

What explains the riot of colors during the leaf viewing season? Why do some trees turn yellow, others turn red, and then they turn brown.

The explanation lies in the replacement of chlorophyll with other substances: carotenoids and anthocyanins. In summer, trees have a lot of nutrients, but with the arrival of autumn, this supply gradually decreases. With the depletion of reserves, the synthesis of chlorophyll stops. And then other pigments that are present in the leaves, but overlapped by the green color - yellow and orange - become noticeable. These are the same pigments that determine, for example, the color of carrots - carotenoids.

Leaves with red hues are the result of the formation of anthocyanins. IN green leaves these pigments are missing. They begin to form in the leaves of some plant species after the disappearance of chlorophyll. Anthocyanins are the same pigments that make radishes, geraniums, roses or cauliflower have their own color.

The brightness of the color of autumn leaves depends on the weather. Trees wear their most beautiful clothes in sunny, dry weather, at a temperature of 0 - 7 degrees Celsius. If the weather is cloudy and rainy, then the leaves do not burn, but turn into dull yellow shades or even turn brown.

As winter approaches, yellow and red leaves gradually lose their pigments. Brown leaves, which can be seen in late autumn, with the onset of severe cold, after snowfall, these are leaves in which there are no pigments left at all, and cell walls have become visible.

What color are the leaves of trees in autumn?

Birch leaves are yellow-golden in autumn

Maple leaves are red in autumn