Trees and shrubs in autumn. Autumn changes

Table of contents

Introduction …………………………………………………………………….2

My Observations…………………………………………………………3

Questioning classmates ………………………………………..3

3. The role of leaves in the life of a tree………………….................................................... .....4

4. Why do leaves change color? ................................................. ..................4

5. Folk signs…………………………………………………………..5

6. How does leaf fall occur? .............................................. ...............................6

7. Why do trees shed their leaves? .............................................. ...............7

8. The value of fallen leaves in nature…………………………………..8

Conclusion ………………………………………………………………….10

List of information sources used.………………………11

Appendix……………………………………………………………………12

Introduction

In a golden carriage with a playful horse,

Autumn galloped through the forests and fields.

The good sorceress changed everything,

Brightly - yellow painted the earth.

Autumn is a wonderful time of the year. Leaf color change is one of the first signs of autumn. Lots of bright colors in the autumn forest! Birches, maples turn yellow, patterned rowan leaves turn crimson red, aspen leaves turn orange and crimson. At this time of the year, I like to wander through the autumn park, breathe fresh air, observe nature, collect bouquets from fallen leaves, admiring yellow, crimson, purple colors.

Once, I was collecting foliage for crafts, and I became interested. Why do leaves change color in autumn? Why couldn't even pick them in the summer strong wind, and in the fall they come off themselves? What happened?

And here comes the speculation:

1. The leaves on the trees are old, they are cold, so they fall off.

2. The leaves are getting dark.

3. Leaves fall from the wind.

To test my assumptions, I set myself following goals and tasks:

Objective: Find out - why are the leaves falling?

Tasks:

1. Find out the meaning of the leaf in the life of the plant.

2. Watch the leaves change in autumn.

3. Establish the causes of leaf fall.

4. Make a herbarium from autumn leaves.

To solve these problems, I had to read the literature on this issue, contact a biology teacher on this issue, and study Internet sources.

1. My observations

I watched the leaves change in autumn.

In September, yellow leaves appeared on some trees, but the connection with the branches was still strong. (see annex 1)

In October, almost all the leaves changed their green color to yellow, brown, red, and leaf fall began. (see annex 2)

In November, almost all deciduous trees shed their leaves.

The last to get rid of the leaves - willow. (see annex 3)

2. Questioning of classmates and students of the school.

At the beginning of the study, I decided to conduct a survey

their classmates and students of our school to find out if they know why a tree needs leaves, why leaves change color and fall in autumn. (see appendix 4,5,6)

The results were as follows: to the question why the tree needs leaves, among classmates only 2% of students answered correctly, among grades 1-4 the correct answer was 12%, students in grades 5-9 answered 25% in the affirmative, and 10-11 grades - 32%.

When asked why the leaves change their color, classmates were able to correctly answer -5%, grades 1 - 4 -14%, grades 5 - 9 - 28%, grades 10 - 11 - 41%.

Why the leaves fall in autumn, classmates answered correctly - 4%, grades 1 - 4 - 18%, grades 5 - 9 - 22%, grades 10 - 11 - 37%.

Analyzing the results of the survey, I found that most students do not know the reasons for the change in the color of autumn leaves and the reasons for their fall.

The role of leaves in the life of a tree

I studied the structure of the leaf and found out that the leaf consists of two parts: the leaf blade is what we used to call the leaf, and the petiole is its stalk. (see annex 7)

With the help of the petiole, the leaf is attached to the branch.

On the leaf blade, the veins are very clearly visible, especially from the underside. They pass into the petiole. It turns out the veins are the vessels through which water and nutrients move. But if we look into the middle of a green leaf, we will see that each leaf is full of wonderful green chlorophyll grains. (see appendix 8) The grains are so small that they cannot be seen. And yet each such grain is, as it were, a tiny factory. They cook food for the whole tree. These factories take from the air invisible carbon dioxide. From this gas, water and substances dissolved in it, extracted by the roots, wonderful grains are made construction material for new branches, buds, roots and, of course, for the trunk itself. Just as a new house cannot rise without concrete and brick, so a tree cannot grow without the material prepared by the green seed-plants. Green plants get their energy from the sun. Tiny chlorophyll grains catch the light from morning to evening. AT green color they are colored by chlorophyll, which is constantly destroyed and restored again thanks to sunlight.

Conclusion: green leaf necessary for the tree, as it prepares food and new building material for the whole plant. The yellow leaf interferes with the tree. It consumes a lot of moisture, but the tree does not nourish.

Why do leaves change color?

After studying the literature, I found out why the leaves change color in autumn. In summer, the sun shines for a long time, 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. Plants receive less light. Chlorophyll is destroyed during the day, but does not have time to recover. The green color in the leaf decreases, and the yellow becomes more noticeable: the leaf turns yellow.

But in autumn, the leaves become not only yellow, but also red, crimson, purple. It depends on what coloring matter is in the withering leaf.

The autumn forest is rich in its colors! The brightness of autumn leaves depends on what the weather is like (see Appendix 9.10).

If the autumn is long, rainy - the color of the foliage from excess water and lack of light will be dull, inexpressive. If cold nights alternate with clear sunny days, then the colors will match.

weather - juicy, bright.

Alder and lilac leaves will fall green, regardless of the weather. In their leaves, except for chlorophyll, there are no other coloring substances. (see annex 11)

Folk omens

People have been observing nature for a long time, noticing everything that happens around. And among the people there were signs associated with a change in the color of the leaves.

The leaf, although it has turned yellow, 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 on the trees will appear yellow leaves- by early autumn.

Until the leaf from the cherry trees has fallen, no matter how much snow falls, winter will not come.

bony leaves Before bad weather, they bend up, and before good weather, they twist down.

If birch lowers its leaves forward, then wait for a dry summer, and if alder and maple, then wet.

If in the spring the birch leaves the leaves before the alder, the summer will be windy, and if the alder blossoms earlier, then colds and rains will be frequent in the summer.

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

If the oak buds and leaves earlier than the ash, then the summer will be wet and cool. If the ash tree blooms earlier, then the summer should be dry and warm.

How does the leaf fall come?

No one tells a tree when to shed its leaves. But now autumn is approaching - and the leaves on the trees change their green color. Nutrients begin to be pulled from the leaves into the trunk.

Changes also occur in the petioles of the leaves. The petiole consists of "bricks" (cells) and thin tubes (vessels), through which nutritious juices come from the tree. Leaves need them for growth and development. In summer, the “bricks” are firmly interconnected and just as firmly attach the leaf to the branch.

Try picking a green leaf, for example, from a birch. It is easier to break than to separate without any damage.

And in autumn? The more yellowed or reddened the leaf, the easier it breaks off. And there comes a moment when you just have to touch the leaf, as it immediately falls from the branch.

In autumn, the bonds between the bricks in the petiole are destroyed because the chlorophyll grains that produced the building material for the entire tree have collapsed. A special cork layer is formed. It is like a partition between the petiole and the branch. The leaf is held only on thin tubes. (see annex 12)

To prove this scientific fact, I conducted an experiment.

I took two branches: broken by the wind in the summer, and in the fall. I tried to tear off the sheet from the first one. The leaves on it had long dried up, crumbled easily, but came off badly. I tried to tear off a leaf from a branch that was not damaged in the summer. The sheet came off very easily.
Examined with a magnifying glass autumn twigs different trees I did not find wounds from fallen leaves on them.

Conclusion: the leaves do not break off the branches, but separate in a certain place - where the petiole is attached to the branch, and where a cork layer forms in autumn. (see appendix 13)

7. Why do trees shed their leaves?

Although our deciduous trees live for tens, often hundreds of years, their leaves "work", only one season.

All in a green leaf bottom surface, covered with a transparent skin, dotted with small holes - stomata. Under the influence of ambient temperature and air humidity, they either open or close. Like windows in houses. The water that the root sucks up rises along the trunk to the branches and leaves. When the stomata are open, moisture evaporates from the leaves, and new portions of water are pulled up through the trunk into the crown.

The sun heats the leaf, and the evaporation cools it. Trees need a lot of water. During the summer, a large birch, for example, evaporates about 7 tons of water. In winter, you can’t get so much moisture from the soil. Winter for trees is not only cold, but also, most importantly, dry season. By losing their leaves, the trees protect themselves from the "winter drought". Trees do not have leaves - there is no such abundant evaporation of water. (see annex 14)

In addition, leaf fall is needed for trees in medicinal purposes.

It turns out that the plant receives from the soil not clean water, and solutions of various salts. These salts, passing along with water through the whole plant, also enter the leaves. Part of them goes to feed the plant, while the part that remains unused is deposited in the cells of the leaf. As a result, by autumn, the leaves become, as it were, mineralized, abundantly saturated with salts, the deposits of which in some cases can even be seen under a microscope. A large number of mineral salts deposited by autumn in the leaves disrupts their normal operation and becomes harmful to the plant. (see annex 15)

In cities, the air is heavily polluted by smoking chimneys of factories and plants. The smallest particles of soot settle on the leaves, clog the stomata. Evaporation slows down. The sheet is weighted inside - with mineral salts, and outside - with urban soot, and a light gust of wind easily breaks it off.

(see annex 16)

I did an experiment. Plucked from a tree autumn leaf and rubbed sheet plate with a clean, damp swab. The tampon is dirty.

Conclusion: leaves trap dust, urban soot and various substances from the air, which means that the stomata of the leaf become clogged, evaporation slows down. An excess of mineral salts accumulates inside the leaf. The leaf becomes heavier, a slight gust of wind rips it off.Dropping their leaves, trees protect themselves from "winter drought", mechanical damage under the pressure of snow and poisoning. harmful substances accumulated in the sheet.

8. Significance of fallen leaves in nature

Fallen leaves are indeed of great importance in nature.

1. We noticed that the leaves dry out under the action of the sun, begin to crumble, turning into dust. Under the influence of rain, snow, and also due to the work of certain microorganisms, they rot, gradually mixing with the ground, forming humus. It turns out that fallen leaves are a valuable organic and mineral fertilizer for the same trees from which they flew! (see annex 17)

2. Leaf litter has been found to be a very poor conductor of heat. And together with a thick layer of snow throughout the winter, it insulates the roots of trees, protecting them from frost, and preserves plant seeds. Serves as a blanket for the tree. If you dig up the snow, you can see small sprouts through the packed foliage. And in each sprout, future leaves merged with the stem and even flower buds are distinguished. (See Appendix 18)

3. In spring, water accumulates in a thick leafy blanket, like in a sponge, which gradually flows to the roots of trees and shrubs, nourishing them, supplying moisture and mineral salts valuable for their growth. Nutrients from rotted leaves are reabsorbed by the roots. It is noticed that the land devoid of forest litter is drier. Soil dries out quickly after rain open areas. And under the leaves remains wet for a long time.

4. In summer, leaf litter saves the soil from dangerous compaction. After all, the soil should be loose, rich in air and moisture. Only then will plants grow on it. If you destroy the leaves - the soil is quickly compacted, depleted.

5. It should be mentioned that during the overdrying, the foliage releases physiologically active substances that contribute to the recovery of patients. Trees and shrubs deprived of their forest floor become weaker, more vulnerable to pests and disease.

6. Living beings hide in fallen leaves:

ladybugs

Ants

ground beetles

earthworms

They exterminate various pests of plants and participate in the processes of soil formation. (see annex 19)

7. Can't do without fallen leaves and hedgehogs. In winter, hedgehogs hibernate. In autumn, they build a hut for future wintering, which they often build between the horses of trees protruding from the ground, in hollow stumps, sometimes in burrows or in small natural depressions in the ground, or simply on level ground - among the mass of brought shoots and leaves of plants. Warming the future winter apartment, hedgehogs drag more fallen leaves, plant stems, dry grass and loose moss there in the fall. (see annex 20)

8. Mushrooms cannot do without the forest floor. It is a vital basis for them. After all, the mycelium, being under the rays of the sun, can dry out and die. Leaves and moss protect it from drying out. When picking mushrooms, you can not scatter the leaves under which they hide. You just need to carefully twist the mushroom or cut it with a knife. (See Appendix 21)

9. Fallen leaves are needed by many forest animals. Under it, for example, acorns and shoots of plants that feed on wild boars are stored for a long time.

10. Indirectly, forest litter is also necessary for birds. They rake the leaves in order to find in them small insects and larvae, as well as preserved plant seeds.

11. For us, schoolchildren, leaf fall also brings a lot of joy. Leaves can be made beautiful picture, sticking them at will on cardboard, you can weave beautiful wreaths, make crafts. Similar work develops creative imagination awaken the fantasy. (see annex 22)

The fallen leaves crunch underfoot. And how fun it is to collect the leaves in a pile and then jump into it! This game brings joy, develops dexterity and speed.

There is another assertion that the smell of rotten leaves has a beneficial effect on nervous system relieves fatigue. I love autumn for its colors and special aroma!

Conclusion

Summing up research work, I can conclude that the goal that I set was achieved. I studied why trees fall so easily in the fall, and compared sound and scientifically proven findings with the results of research on the topic.

The hypotheses that I put forward at the beginning of the study were not confirmed. Leaves do not fall from trees because they are cold and old.

The real causes of leaf fall are as follows:

1. Lack of sunlight

Chlorophyll is destroyed, new building material is not produced in the leaf, connections between cells in the petiole are destroyed. A cork layer is formed. The leaf is held only on thin tubes.

lack of moisture

The leaves of the tree in their totality have very large area, and water is rapidly evaporating from all this area. In summer, the tree is able to compensate for the loss of moisture by extracting water from the soil. But with a cold snap cold water from the soil is greatly reduced. It gets in the way correct work leaf and tree life. If the tree had not dropped its leaves, it would have been in danger of drought.

3. Excess minerals

The leaf becomes heavier and barely holds on to the branch, the wind easily rips it off.

During leaf fall, the tree gets rid of excess mineral salts that could poison it.

Fallen leaves are of great benefit to the forest, animals, insects, and therefore to us - people. After all, we are part of nature, and this should never be forgotten. (see annex 23)

During the study, I collected, studied the leaves of trees. He made a herbarium and compositions from this natural material.

List of sources of information used.

1. Big encyclopedia of the student / trans. from French Bogatyrevoy E., Zemtsova T., Lebedeva N. - M .: LLC Publishing House Astel: LLC Publishing House AST, 2003, p. 711;

2. The Big Encyclopedia of the Erudite, - M: Makhaon, 2004, p. 487;

3. Children's encyclopedia "Forest World"; Moscow Makhaon, 2006

4. Why and why / encyclopedia for the curious, ed. Pokidayeva T., Frolova T., - M.: Makhaon, 2007, p. 255 ;

5. Why in autumn - leaf fall? / G. Graubin, - M: Malysh Publishing House, 1990

6. Your first encyclopedia "Forest Life"; Moscow "Makhaon", 2004

7. Why in the fall - leaf fall? / G. Graubin, - M: Malysh Publishing House, 1990

8.http://go.mail.ru/search

9.http://www.ezosite.ru/token/pogoda/pogoda_658.html

10.http://geoman.ru/books/item/f00/s00/z0000068/st015.shtml

11.http://nplit.ru/books/item/f00/s00/z0000053/st019.shtml

12.

If the trees did not shed their leaves for the winter, they would die. There are several reasons for this.

Reason one. The leaves of the tree in their totality have a very large area, and water evaporates intensively from all this area. In summer, the tree is able to compensate for the loss of moisture by extracting water from the soil. But with cooling, the extraction of cold water from the soil is greatly reduced; in winter, it is completely difficult to extract moisture from frozen soil. Trees with deciduous cover in winter would die from lack of moisture, that is, they would dry out.

For the same reason, with the onset of the dry season in the tropics and subtropics, the trees in these climatic zones shed their leaves and stand bare until the rainy season arrives.

The second reason. Have you noticed that after heavy snowfalls, the branches of trees strongly lean towards the ground under the weight of snow? Some branches even break from it. If the leaves remained on the trees in winter, then much more snow would linger on the branches, since the leaf surface, as we said above, is large. Thus, dropping their leaves in autumn, the trees protect themselves from mechanical damage under the pressure of snow.

Reason three. During leaf fall, the tree gets rid of excess mineral salts that accumulate in the leaves throughout the summer. As we have repeatedly noticed, the sheet intensively evaporates water. To replace this evaporated water, new water constantly enters it, which is sucked in by the roots from the soil. But in the water that the roots get from the soil are dissolved various salts. Thus, the leaves do not receive pure water, but saline solutions. 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 it mineralizes by autumn. As a result, by autumn, the leaves accumulate a lot of salts, becoming, as it were, mineralized. An excess of mineral salts disturbs normal work leaves. Therefore, shedding old leaves is necessary condition to keep the plant alive.

By the way...

How do conifers manage not to lose moisture in winter, while remaining green? The secret is that the needles evaporate many times less moisture than the leaves. Firstly, the surface of the needle is many times smaller than the surface of the leaf; secondly, the needles have a thick skin; thirdly, they are covered with a wax coating, which also reduces the evaporation of water. Finally, the stomata in the needles are located in special recesses - this reduces the intensity of moisture evaporation through them.
Coniferous trees also shed their cover, but not at once, as they do hardwoods, but gradually: coniferous needles live, on average, 3-4 years. Therefore, the change of "clothes" of conifers goes unnoticed.

If the trees did not shed their leaves for the winter, they would die. There are several reasons for this.

Reason one. The leaves of the tree in their totality have a very large area, and water evaporates intensively from all this area. In summer, the tree is able to compensate for the loss of moisture by extracting water from the soil. But with cooling, the extraction of cold water from the soil is greatly reduced; in winter, it is completely difficult to extract moisture from frozen soil. Trees with deciduous cover in winter would die from lack of moisture, that is, they would dry out.

For the same reason, at the onset of the dry season in the tropics and subtropics, trees in these climatic zones shed their leaves and stand bare until the arrival of the rainy season.

The second reason. Have you noticed that after heavy snowfalls, the branches of trees strongly lean towards the ground under the weight of snow? Some branches even break from it. If the leaves remained on the trees in winter, then much more snow would linger on the branches, since the leaf surface, as we said above, is large. Thus, dropping their leaves in autumn, the trees protect themselves from mechanical damage under the pressure of snow.

Reason three. During leaf fall, the tree gets rid of excess mineral salts that accumulate in the leaves throughout the summer. As we have repeatedly noticed, the sheet intensively evaporates water. To replace this evaporated water, new water constantly enters it, which is sucked in by the roots from the soil. But in the water that the roots get from the soil, various salts are dissolved. Thus, the leaves do not receive pure water, but saline solutions. 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 it mineralizes by autumn. As a result, by autumn, the leaves accumulate a lot of salts, becoming, as it were, mineralized. An excess of mineral salts disrupts the normal functioning of the leaves. Therefore, dropping old leaves is a necessary condition for maintaining the normal life of the plant.

By the way...

How do conifers manage not to lose moisture in winter, while remaining green? The secret is that the needles evaporate many times less moisture than the leaves. Firstly, the surface of the needle is many times smaller than the surface of the leaf; secondly, the needles have a thick skin; thirdly, they are covered with a wax coating, which also reduces the evaporation of water. Finally, the stomata in the needles are located in special recesses - this reduces the intensity of moisture evaporation through them.
Coniferous trees also shed their cover, but not at once, as hardwoods do, but gradually: coniferous needles live, on average, 3-4 years. Therefore, the change of "clothes" of conifers goes unnoticed.

Autumn is the season for leaf fall. Remember from Pushkin: “The forest drops its crimson dress ...” It drops it - beautifully, majestically, slowly. The trees are not exposed at once, giving us the opportunity to enjoy the autumn metamorphoses. It is the end of October, and the handsome poplars are still green, while the chestnuts are almost completely exposed. Lindens, birches, elms shed their leaves already in September, lilacs stand elegant until the first frosts, and coastal willows can keep their leaves until the first snow. Different trees have different leaf fall times. Sometimes even trees of the same species, growing side by side, part with their leaves at different times from year to year. Why? And the tree has its own reasons for this, only it knows the reasons.

Leaf fall can be uneven and last for several weeks. In linden and poplar, the leaves fall first from the lower branches, then the middle is exposed and at the end the top of the tree flies around. And the elm, hazel, and ash begin to shed their leaves from their upper branches. But in November, with the first frosts, a real full-scale leaf fall begins. The leaves fall often and thickly, like snow, covering everything around with a multi-colored carpet. On the one hand, this carpet protects the roots of trees from freezing, and on the other hand, it serves good fertilizer for soil.

Apparently, this phenomenon once impressed our ancestors so much that in Ukrainian, for example, the last autumn month so it is called - leaf fall. So what is the reason for this phenomenon, why do trees shed their leaves in autumn? There are several reasons for this.

First, by shedding its leaves, the tree protects itself from water loss in winter. After all, moisture constantly evaporates from the surface of the leaves. It rains in spring and summer, and the tree easily compensates for these losses by extracting water from the soil. And in winter, the ground freezes, so it is very difficult for the roots of trees to extract it from the frozen soil. And if the tree did not shed its leaves, in winter it would simply dry up. And so, there are no leaves - there is no abundant evaporation of moisture.

Secondly, this is how the tree gets rid of excess mineral salts and harmful products vital activity, which by the fall in the leaves accumulates a huge amount. After all, an excess of mineral salts disrupts the normal functioning of a tree, and toxins accumulated over the summer can easily be poisoned. Therefore, the dropping of leaves also occurs for medicinal purposes, being a necessary condition for further normal life.

Thirdly, by dropping leaves, the tree protects its branches from injuries and fractures. After all, a lot of snow will not hold on bare branches, but leave the crown of a leafy tree for the winter and, because of large surface leaves, there will be much more snow on the branches. Many branches will not withstand such weight and will break or bend.

In a word, leaf fall is a biological adaptation, preparation of a tree for life in winter conditions. If the trees did not shed their leaves in autumn, they would simply die in winter. Leaf fall developed in the process of long evolution and entered the natural rhythm of life. Following this rhythm, the trees prepare in advance for winter.

Leaf fall is a hereditary feature of deciduous trees. Even growing a tree in a greenhouse with acceptable living conditions, it will still drop foliage at a certain time. Because it is so conceived by nature itself.

Falling leaves before the onset of winter - biologically useful device some perennials to life in certain climatic conditions. ?

leaf fall

leaf fall is a seasonal phenomenon. It occurs mainly in connection with the approach of the unfavorable season for the active life of plants - winter.

Leaf fall is the beauty of autumn. forest, park, individual trees and bushes are decorated in different shades yellow, orange, purple flowers. And in this bouquet of colors, austere spruces and fluffy pines stand out even more clearly with bluish juicy greenery.

For some reason, on different days, they crumbled more strongly different breeds trees, - on the third day all the paths were covered with maple leaves, yesterday they were covered with lemon leaves of lindens, and today purple aspen leaves with black veins began to fall.

K. Paustovsky

climate change

It is believed that the moderate climate central Europe with warm and cold seasons was preceded by a warm and hot climate. It was getting colder slowly, so seasonality came on gradually.

It was in such conditions that the modern vegetable world temperate zone of our country and developed the adaptability of plants to life in winter time. Leaf fall is one of the adaptations that help plants endure cold.

• Why don't all trees and shrubs lose their leaves in autumn?
• Why different plants this process goes differently: and the time of leaf fall is different and the colors of the leaves are not the same?
• Why do signs of the onset of leaf fall appear in some trees when there is still no trace of autumn?

What is the use of a tree from shedding leaves

We can talk about leaf fall as a useful device that helps the plant survive the cold season. What is the use of a tree from shedding leaves?
This can be seen if you visit the forest in the dead of winter after heavy snowfalls, slowly making your way on skis through deep, loose snow, along a path familiar from summer.

How this path has changed! early autumn when they went for mushrooms, it was wide enough, and nothing blocked their path. And now various obstacles constantly arise here. Here is a young birch leaning to the ground, crushed by a layer of snow, blocking the road.

A flexible mountain ash is bent in an arc in the middle of the path, and it is necessary to release its top, covered with snow. Young in places tall trees, bending the tops, form a real arch.

On the big trees- whole pillows of snow. Snowflake after snowflake he settled on the branches of birches, aspens, oaks, on the elastic paws of fir trees, lowering them down. Sometimes a branch bent under the weight of snow drops fluffy clods and quickly straightens up, suddenly freed from this load. But you can also see broken branches.

It turns out that, losing leaves, the plant does not suffer, and it is certainly more profitable for it to start in the spring. New Year living with young foliage than surviving the winter with old.

evergreen vegetation

But how are vital functions carried out in plants that do not have leaf fall?

There are no such perennial plants that do not lose their foliage at all in nature. The only difference is that some plants lose them with the onset of an unfavorable time of the year for life at the same time, while for others, leaf fall occurs gradually.

This applies equally to the plants of temperate, cold and hot countries. In the latter, if there is no dry period, trees and shrubs tend to remain evergreen. all year round, but also constantly changing leaves.

According to the descriptions of travelers, and among the trees of the humid tropics, where there is no drought, there are those that lose all their leaves at the same time. But after a week or two they show off in young foliage. Here, the significance of leaf fall as a means of liberation from accumulated excess substances appears even more clearly.

However, in most cases, the change of leaves in evergreen trees and shrubs carried out gradually. Each year, these plants lose only part of their foliage. So, spruce needles live for about seven years, so an adult spruce annually loses about a seventh of its foliage-needles. Pine needles live only two or three years, so the pine tree has a more noticeable leaf fall.

If mushroom pickers collected in a young pine forest, they could not help but notice that in your basket, along with mushrooms, you have a lot of dried pine needles. At this time, before the onset of autumn, near the pine and some of our other coniferous trees and the most significant leaf fall occurs. When picking mushrooms, you touch a branch, and the yellowed needles fall to the ground.

Evergreen deciduous trees and shrubs have a similar change of leaves. A palm tree, for example, throws out more and more new leaves from above, and the lower ones continuously die off and dry up.

Such leaf fall is also observed in many other plants of warm countries.
An interesting phenomenon, similar to leaf fall, is observed in trees, shrubs and semi-shrubs of deserts.

These plants either have no leaves, or they are very small. Sometimes they resemble scales, sometimes they turn into spines. Such plants include saxaul, sand locust other.

With the onset of hot weather, plants that do not have leaves at all and assimilate organic matter with the help of thin green twigs, for example, black saxaul, a real branch fall occurs - thin, assimilating branches fall. Biologically, such a branch fall is fully consistent with the leaf fall of our trees, which lose their leaves in autumn.

Little noticeable leaf fall in the north. Here is the winter after short summer usually comes quickly, rapidly, and many dwarf, squat shrubs, as well as herbaceous plants go under the snow green, some even with flower buds. Northern plants have developed great cold tolerance, and after spending the winter under the snow, they continue to develop in the spring. bright colors there is no leaf fall here.

Wherever leaf fall is observed, its beauty cannot be compared with the leaf fall of temperate countries, with our golden autumn.

Features of leaf fall

Why is our autumn the most elegant in the world? It turns out that because it is our longest. Here, nature is slowly preparing for the transition from summer to cold weather, when active life freezes.

Every tree, every shrub has its own leaf fall features. Therefore change autumn pictures goes in a certain sequence, constituting feature our nature. Orange, golden crimson become the dying Maple leaves, and the old one is especially attractive at this time. A modest beauty competes with him, attracting little attention in ordinary times. It stands out among other trees with a bright crimson spot.

The leaves of many trees and shrubs take on various shades of yellow. Larch trees become yellow-straw, some kind of faded uniform yellow color appears in the leaves, leaves are covered with variegated yellowness (due to uneven yellowing).

And how wonderful in color some shrubs and small trees become at this time! Viburnum stands out with purple leaves of different brightness, euonymus bushes take on a light pink color, and crimson leaves definitely help birds - lovers of berries - to see branches hung with orange clusters from afar.
Who plays the role of the artist who creates this colorful splendor?

The leaf, as you know, is an assimilating organ. It carries out difficult process photosynthesis, which involves many different substances, complex chemical changes occur.

In addition to chlorophyll, there are other colored formations in the foliage. In normal times, the green color of chlorophyll, (more:) covers, or, as they say, fixes, other colored substances of the leaf, they become invisible. But by autumn, the usual processes change radically.

Why do leaves change color in autumn

The complexity of the phenomena occurring in the leaf at this time can be judged from such examples. It is known that chlorophyll occurs under the influence of the sun. He is an indispensable participant. In autumn, a significant change occurs: under the influence of the sun, chlorophyll is destroyed, new substances are formed, this is manifested in a change leaf colors.

As a result of the destruction of chlorophyll in the leaf, through the transparent skin, something is revealed that is not noticeable in summer and that arose in autumn, due to the attenuation of the metabolic process. It was at this time that a series beneficial to the plant substances leave the leaf to the stem and root.

A variety of physiological processes occurring in the leaves are reflected in their color. And since each plant has its own characteristics developed during its life, the difference in the color of the leaves in autumn is very large.

Observing leaf fall from year to year, one can easily detect its features in different woody plants in different years. If the autumn is cloudy, without sunny days, then the leaf stays on the tree longer and changes in color less. Leaf fall in such an autumn is much less bright - there is no crimson color on the leaves of aspens and maples, yellow color prevails in the forest.

The process of leaf death

Strong early frosts also change the course of leaf fall. They speed up leaf death process, and all normal changes then it does not happen: frost kills the still living tissue of the leaves and disrupts the normal course of processes occurring during leaf fall. Bright sunny days, on the contrary, contribute to the colorfulness of leaf fall. This is likely because bright light speeds up the breakdown of chlorophyll.

How sensitively plants respond to insignificant changes in the conditions in which leaf fall occurs can be judged by this fact. Two trees of the same species, but growing in conditions that are not exactly the same, will fall leaf differently.

In this case, the microclimate will influence, that is, minor, often barely perceptible climatic features, depending on the height of the area, humidity, protection from winds, lighting, etc.

Highly important point in leaf fall - the formation of the so-called separating layer.
Tear off a leaf from a branch in the summer, at the heyday of his life, and look at the place of separation with a magnifying glass: you will see a gaping wound. But if you are on time autumn leaf fall pick up a freshly fallen leaf and look at the place where the petiole is detached from the branch, then make sure that it is completely smooth.

The same smooth surface is also available at the place of separation on the branch. This is the separating layer, which separates the tissues of the leaf and tree in the fall. It began to form in the summer, long before the leaf fall. That is why the dry leaves of a broken branch do not fall off, the leaves of a birch or maple broom do not come off - a separating layer could not yet form there.

Try growing a small deciduous tree in the room. No matter how much you take care of it, autumn will come, and the leaves will fall off, as a separating layer has formed between them and the branch. This useful adaptation arose historically and is already a hereditary property of plants.

Leaf fall of trees and shrubs is only one of the most striking phenomena of preparing plants for winter. Adaptation to the experience of winter is manifested in perennial plants throughout the body.

Laying new kidneys

So, simultaneously with the appearance of a separating layer, the formation laying of new kidneys, and already at this time it is determined what kind of buds it will be - leafy or flower. After laying, the buds stop developing, that is, they are at rest until the beginning of the growing season - until spring.

It is very interesting that such a kidney is absolutely necessary cold period: before a certain time, it cannot grow. If you cut branches in the fall, after leaf fall, or in the first half of winter and create all the conditions for them to grow, then the buds will not open, because the plant has not yet completed the period of rest it needs, and therefore it cannot develop.

But the branches taken in January - February and lowered into the water begin to live actively, form leaves, and if the buds are flower, then flowers. Therefore, the rest of the plant in winter is not absolute. During this period, physiological changes occur in the plant.

Seasonal changes in trunk and root

AT stem (trunk) and root during the preparation for winter are also observed changes. Many substances from the leaves pass into the trunk and contribute to the plant's transfer of winter cold. The root at this time grows intensively even after leaf fall, before frost; it continues its growth in the spring, as soon as the earth thaws, although the leaves have not yet blossomed.

As you know, the heredity of a plant can change. The plant can adapt to new living conditions. It is interesting to see how the plant will behave if temperature regime to which it has adapted will be broken.

If the changes occur very abruptly, then the plant, of course, will simply die. A heat-loving plant cannot immediately become cold-resistant. But change temperature conditions within certain limits, it can cause such adaptive features in a plant that will enable it to exist safely in a more severe climate.

Features of leaf fall in oak

Interesting in this regard. There are two closely related species of oak - winter oak and summer oak. By appearance they are hardly distinguishable, but differ significantly in leaf fall. Autumn frosts usually take the winter oak by surprise, when the tree is not yet prepared for leaf fall. Frost kills the leaf, and the tree stands with browned foliage almost all winter. Obviously, the winter oak has come to middle lane from places where summer is long and leaf fall comes later.

The summer oak loses its leaves in a timely manner, before the onset of frost, and stands without leaves in the winter. Valuable substances that in winter oak do not have time to leave the leaves before frost, in summer oak are stored in the branches and trunk.

However, studies and experiments on the distribution of oak to the north show that it is not the summer oak, but the winter oak that has more chances for settlement here. The summer oak, which loses its leaves early, renews them early. Winter oak, on the contrary, loses and renews foliage later..

Therefore, in places where there are late spring frosts, frost often kills a young leaf of a summer oak, while a winter oak that leaves later does not suffer from it. And what is better - to lose ahead of time an old, already worn-out leaf or a young, spring one, is already known.

A naturalist is working on riddles and questions of leaf fall.

The question why trees shed their leaves is not only interesting, but of great importance. practical value for the acclimatization of plants, that is, their artificial movement to places that differ significantly in physical and geographical conditions, in particular, a different seasonal temperature.