Why do leaves change color in autumn?

Research work “Why change leaves change the color in autumn”

In research, the role of leaves in the life of trees explains why the leaves change color and autumn in autumn. The experiments carried out and described show the secret of the autumn colors, show the destruction of chlorophyla in the leaves and demonstrate the breath of the leaves.


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In research, the role of leaves in the life of trees explains why the leaves change color and autumn in autumn. Spent and 91 KB


Autumn is the most mysterious time of the year. It sneaks quietly and imperceptibly. The leaves replace their color from green to golden and turn into a light and warm bed break and change everything. At this time of year it is good to hike in the autumn park, to breathe fresh air, to watch nature.

Once when I went with my mother in the autumn park, I noticed the leaves in the color on a branch of a tree: yellow, green and red. There were also many colorful leaves under the trees, and I collected a nice autumn bouquet of them. I was interested in the question of why the leaves were green in summer and in autumn they were colored several times. Last year I studied the topic “Why the leaves are green” and this year I decided to continue my studies and find out why the leaves change the color.

My work is to find an interesting and unusual nearby and to watch and study.

The purpose of my work is

Find out why the leaves change color in autumn.

  • Study literature, Internet materials on the subject of research;
  • Prepare profiles and carry out surveys among the students and their parents;
  • Find out why the leaves change the color in autumn several times.
  • Do experiments:
  • Determine that the leaves breathe;
  • Determine that the leaves contain different color substances;
  • Perform experiments to find out how sunlight affects the color of the leaves.
  • To analyze the results, draw conclusions.

Examination subject: Leaves of autumn trees.

  • studying literature and materials from the Internet on this topic;
  • Analysis of the information obtained.
  • Questionnaires of students and their parents and the construction of diagrams;
  • Carry out experiments and experiments.

The leaves change the color because they contain different color substances; The sun affects the color of the leaves.

1. The main part.

1.1. What are the leaves for wood?

To understand why the leaves change the color in autumn, you have to find out why the trees need leaves.

Nothing happens in nature and the leaves on the trees also have their own purpose. Liszt is an extremely important organ of the plant. With the help of leaves, trees and food breathe. The leaves of plants contain chlorophyll. Saccharosis is generated under the influence of light sunlight in the leaves. It is required for the growth of wood and maturation of fruits. The leaves also take part in the air exchange with the environment, absorb carbon dioxide and release oxygen. This process is referred to as photosynthesis.

When I carried out research on the subject of “Why Green Leaves” in the second class, I got to know the structure of the sheet. The sheet consists of two parts: a sheet metal plate and a leaf stick. The leaf is attached to the stem with the help of the leaf stole.

1.2. Why do the leaves change color in autumn?

Everyone knows that trees change with the onset of autumn. They seem to be wearing beautiful colorful outfits: red, yellow, purple. Why do the leaves change color in autumn?

The thing is that with the approach of autumn days, the air temperature decreases. The trees are preparing for winter. Less and less water penetrates the leaves – this leads to a slowdown in life processes. They begin to break down the color pigments.

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Chlorophyll is responsible for the green color of leaves. Chlorophyll in a living leaf is constantly being destroyed and regenerated. But it only happens in the light. In summer the sun shines for a long time. Chlorophyll is destroyed and instantly restored. The formation of chlorophyll does not lag behind its destruction. The leaf stays green all the time. Autumn is coming, the nights are getting longer. Chlorophyll is destroyed during the day but doesn’t have time to recover. Chlorophyll is destroyed faster in sunny weather. That is why the leaves keep their green color longer in cloudy, rainy autumn.

In addition to chlorophyll, plant leaves also contain other color pigments, such as xanthophyll, carotene, and anthocyanins. Thanks to them, the leaves acquire a golden yellow, orange, red color. All of these pigments are constantly present in the leaves, but only become visible when chlorophyll production decreases, i.e. autumn. The leaves change color, and the so-called “golden autumn” comes (Appendix No. 1).

1.3. Why do the leaves fall in autumn?

Leaf fall is the biological process by which plants shed their leaves.

Trees whose leaves change color and fall off in the fall are called deciduous trees. Its trunks and branches can withstand winter frosts, but thin, delicate leaves cannot.

As the days get shorter, the trees prepare for winter. The amount of sap in the tree decreases, the leaves grow old. When the leaves turn yellow, a thin separating layer of cells, the so-called cork layer, appears at the base of the leaf. Gradually, this partition breaks the connection between the tree and the leaf. A breath of air is enough and the leaf comes off. On the branch where the leaf is torn off, a small scar is left, overgrown with a protective layer of cork. So, leaf fall is a tree’s ability to steadfastly survive the winter and burst its buds again in the spring.

2. Practical part.

2. 1st Sociological Survey.

Purpose: to determine if students and adults have thought about why the leaves on the trees change color in autumn.

The survey included: students – 52 people, adults – 28 people. They were offered a questionnaire with questions (Appendix No. 2).

The following answers were received to the questions of the questionnaire. (Appendix #3)

From the analysis of the questionnaire data, we learned that the majority of children (76.9%) and adults (67.9%) wondered why the leaves became multicolored.

20 children (38.5%) and the majority of adults (67.9%) believe that the color of the leaves depends on the amount of dye they contain. About the same number of children (40.3%) believe that the leaves change color to protect themselves from various pests.

Almost all children (88.5%) and adults (85.7%) are interested in the scientific explanation of leaf color changes, and few of them are not interested.

Respiration is the most important process of life, characteristic of all living organisms, including leaves. That a person breathes no longer needs to be proven to anyone. But with plants it is much more difficult: how to understand, and even more so how to prove that plants breathe?

To ensure that the leaves of the trees breathe, the following experiment will help.

The purpose of experience: Check whether the leaves of the trees breathe.

To carry out experience, we tore a green leaf out of a tree. I put it in a transparent water bowl and crushed it with a small stone so that it fully plunged into the water. Then she put a bowl in a sunny place. A few hours later I saw that the entire leaf and the edges of the bowl were covered with tiny bubbles. This is oxygen that releases leaves during photosynthesis.

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Conclusion: I was convinced that the leaves of the trees breathed.

“Rainbow of autumn colors”

The green color of the chlorophyll is so strong that it masked any other pigment. When the production of chlorophyll ends in autumn, only pigments become the main dye of the leaves.

The purpose of experience: selection of pigments of different colors from the leaves.

In order to carry out this experience, we collected leaves made of green and yello w-brown. We took the green leaves, lost them and put the resulting porridge in the glass. We did the same with leaves of another color. We poured alcohol into every glass, lowered the white paper strips and went for the night. In the morning we saw that paper strips were painted in a different color.

Conclusion: I was convinced that there are different color substances in the leaves.

In what light do the leaves turn yellow?

The color of the leaves depends on the lighting, the air temperature, the presence of water. In order to identify the effect of light on the color of the leaves, we carried out an experiment.

The purpose of the experiment: Find out how sunlight affects the color of the leaves.

To carry out an experiment, we tore a green leaf out of a tree. I sealed half of the sheet with foil (limited light access). The sheet was placed in a glass of water and placed in a wel l-lit place for a week. A week later I took the film and compared the halves of the leaf. Part of the sheet that was closed was yellow. The results of this experiment confirm my assumption that sunlight affects the color of the leaves. Without light, chlorophyll is destroyed in the leaf and the leaf yellow.

Conclusion: The sheet under the film was yellow, which means that chlorophyll is destroyed faster without sunlight.

The need for oxygen to destroy chlorophyll.

To destroy chlorophyll, further condition is required – oxygen. In order to find out how oxygen affects the destruction of chlorophyll, we will carry out an experiment.

The purpose of the experiment: to prove that chlorophyll is destroyed more slowly without oxygen.

In order to carry out this experiment, I took aging, but still saved the green color, a leaf. I lowered it in a glass of water so that only half of the leaf was under water. The glass lay a dark place. 2 days have passed, there were no changes to the sheet. And only after 5 days did I notice that the part of the leaf that was in the water kept the green color and the other was yellow.

Conclusion: During the destruction of chlorophyll, an important role plays through the breathing process of leaves. There is much less oxygen in the water than in the air. With a lack of oxygen, chlorophyll was destroyed more slowly because the leaf statement process was slowed down.

As a result of my research work, I learned that:

  • The leaves are very important for trees – with their help, trees and food breathe;
  • In addition to chlorophyll, the leaves also contain other color substances that make the leaves colored several times;
  • So that the leaf stays green, sunlight is needed.

I believe that the hypothesis I have put forward to change the color because they have different color substances and that sunlight affects their color.

The experiments we have helped helped me to get the researcher’s skills in order to see clearly what I read about in the books. I will share the information obtained (which was designed in the form of a presentation) in the lesson around the world with classmates.

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Why do leaves change color in autumn?

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  • Why do the leaves change the color in autumn?

Why do the leaves change the color in autumn?

The author of the work was awarded the diploma of the winner of the II graduation

The text of the work is placed without pictures and formulas. The full version of the work is available in the “Files” tab in PDF format

Change the color of the leaves on the trees is one of the first signs of autumn. Many bright colors in the autumn forest! Birch trees, ash and linden trees are yellow, birch bark leaves are pink, patterned Rowan leaves, orange and purple leaves of aspen become pure-red.

The thing is that it is quite cold in regions with a temperate winter climate and not as many sunlight that trees produce energy. The leaves are gentle and cannot survive the winter so that the tree prepares for the cold and takes all advantageous substances from them before they fall.

This is the process of preparing for winter, and that is exactly what the leaves show us their amazing autumn colors. However, there is a good reason why different trees have leaves of different colors. What caused this variety of colors? Everything is a scientific explanation.

Assuming that the plant contains a kind of substance that color the leaves green, and the color changes with the emergence of the cold weather.

The purpose of the project is to find evidence and to scientifically justify the reasons for changing the color of the leaves of trees in autumn.

To solve the goal, it is necessary to solve the following problems:

– study scientific literature on this topic,

– Find the value of the leaves for the tree and determine the reasons for changing the color of the leaves in the autumn period.

– Develop a quest bokelet to visit the autumn park.

Chapter 1. The examination of materials and information about the leaves

1.1. What are leaves and why are they green?

A sheet is an important part of the plant. This is a “Mult i-Store factory”. The main purpose of the leaves is to capture and change the energy of the sunlight. Thanks to the constant work, the leaf eats, emits water vapors, breathes. A square meter of a leaf plate assigns up to four liters of oxygen every hour and takes the same amount of carbon dioxide out of the air.

How long does the sheet live? Leaves of the trees in our region live from spring to autumn. If the leaf is green, it lives. As soon as the leaves are yellow, they blushed, that means they are old and died.

In summer, most trees have green leaves because they contain chlorophyll pigment. Chlorophyll is a pigment in the leaves and colored it green. The pigment is called every substance that absorbs visible light. Chlorophyll absorbs sunlight and uses its energy to synthesize nutrients. During spring and summer, the leaves fall enough daylight that you can produce nourished and chlorophyll regularly.

When we look at the structure of the sheet with a magnifying glass, look at all the veins that lead from the leaf stick out of the sheet, along the leaf of whom is given nutrients, and then you can see that the outer part of the sheet is darker, and only absorbs sunlight. Plants transform sunny color into energy that helps them grow.

This is the process of photosynthesis, which explains why the leaves appear very great and green in the warm season.

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We have carried out experiences that demonstrate the presence of chlofill in plant leaves. We needed a green leaf (we took a leaf from the inner plant), a small piece of white fabric and a wooden object (hammer, cube, a roller pen, etc.).

The sheet was placed in the angle of the fabric and covered with another corner of the fabric. Then a wooden object was heavily pressed on a leaflet in the fabric. When they turned the fabric, they could watch green spots on the fabric. This is the pigment chlorophyll that turns the leaf in green light.

The green leaf of the plant thus makes a chlophil pigment that participates in the process of photosynthesis.

1.2. Why do leaves change their color?

In autumn plant leaves lose their light green color. For example, poplar leaves become golden and on the maple they flash red. Chemical transformations occur in the leaves.

The daily watches get shorter and plants get less sunlight. For this reason, the production of chlorophyll slows down, which leads to a decrease in the green pigment in the leaves. For this reason, the leaves change the color and before they fall out of the tree, important nutrients that can be used are removed from the leaf. The time in which the leaves start to change the color depends more on light than on the temperature, so that the leaves change the color every year at around the same time.

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When deciduous trees reach this light threshold, carbohydrates are transferred from leaves to branches, and new minerals are no longer taken into the foliage. Trees prepare for the separation from them.

Let us try to prove that growth and dropping of leaves depend more on the amount of light than on the temperature. We will perform two simple experiences.

The aim is to find out how light affects the color of the leaves.

Materials: green large leaf; Island or opaque paper, a glass of water.

1. We will have the finest part of the sheet.

2. Put a sheet in a glass of water.

3. Five to seven days in a wel l-lit place for five to seven days.

The photo shows that the leaf has changed the color under the paper, yellowish.

The goal is the same to find out how light affects the color of the leaves.

Materials: internal flower – Ficus Benjamin.

1. Place the flower in a dark place for a week and we will watch.

The result is visible in the photos: after a week in a poorly illuminated place, the plant began to reject yellowed leaves.

So we can come to the conclusion that chlorophyll breaks out faster without light.

With the advent of autumn, plants are prepared for winter. The nutrients slowly move from the leaves to the branches, the trunk, the root and the stocks up there, during the strong cold. When the energy of the stored nutrients is exhausted, the synthesis of chlorophyll stops. The chlorophyll, which remains in the leaves, partially breaks open while pigments are formed of a different color.

1.3. What determines the color of the autumn leaves?

Under the influence of the cold autumn, chemical reactions begin in the leaves that transform chlorophyll into red and yellow compounds. Other components contained in the leaves are also responsible for changing the color – carotene and anthocyans.

Carotine, which are also contained in bananas and carrots, are responsible for yellow, orange and brown colors. Of course there are no carrot trees, but the component itself can be contained in one or the other trees that prevails through anthocyans.

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The red, dark cherry and purple hues of some leaves are due to the formation of the anthocyanin pigment. This pigment colors radish, red cabbage, rose and geranium. If one of the tree species contains more anthocyanins, the leaves will turn red.

Unlike carotene and other yellow pigments, anthocyanin is generally absent from green leaves. It forms in them only under the influence of cold. Like the color of human hair, the color of autumn leaves is genetically determined in every plant species. But whether this color will be matte or bright depends on the weather. The brightest, juiciest colors of leaves appear in autumn, when the weather is cold, dry and sunny for a long time (at temperatures from 0 to 7 degrees Celsius, the formation of anthocyanins intensifies).

Fig. 1 Pigments that color the leaves in different colors

Autumn passes, winter comes. Plants lose their bright colors along with the leaves. 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 breaks. Leaves that no longer receive water dry up and fall from the trees. The yellow or red coloring of the leaves can persist for several weeks after they fall. But over time, the corresponding pigments are destroyed.

Part 2. Development of a quest booklet for a walk in the autumn park

Selection of materials and tasks for the quest

We have decided to present the results of our research in a brochure, but we will do it in the form of a mini quest for our younger sister. For the booklet we need A4 paper, a computer with a text editor installed and a printer to print the booklet.

Tasks for the mini quest:

Gather a collection of leaves while walking in the park. Determine which tree your leaves come from.

Examine the leaves you collected, determine what substances are contained in the leaves. Use a schema. If the leaves are orange in color, then the leaves contain carotene, yellow – xanthophyll, red – anthocyanin.

Color the autumn park.

Dry the collected leaves and put them together into an application.

5. Continuation of the story: he lived and was, grew into himself, grew on a birch in the forest a small green leaf with his brother’s leaves. All summer he was pleased with the warmth, the sun, bathed in the rays of the gentle summer rain. He fell asleep and woke up to the singing of birds that settled in a nest on his birch. But one morning he woke up feeling very cold….

2.2 Creating the layout of the quest booklet

We divided the A4 sheet into three parts and arranged the tasks as follows (the complete booklet is attached).

The leaf is a very important part of the plant. Figuratively speaking, “multi-storey factory”. The main purpose of the leaves is to capture and convert the energy of the sunlight. Leaves are colored green by the pigment chlorophyll, which is involved in photosynthesis.

In the fall, chlorophyll production slows, leading to a decrease in the green pigment in the leaves. The time that leaves begin to change color depends more on light than temperature, so the leaves in our strip change color around the same time each fall.

The simplest answer to the question “Why do leaves change color in autumn?” it sounds something like this: In autumn, when the days get shorter and the temperature drops, the leaves stop producing the green pigment chlorophyll, turn yellow and fall off.

Thus, the hypothesis we made at the beginning of our study was partially confirmed.

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