Why do leaves change color in autumn? Autumn leaf color and leaf fall Why leaves change color in autumn

Ministry of Education, Science and Youth of the Republic of Crimea

Republican competition of natural history projects for junior schoolchildren "Pioneer"

Section: "Plants around us"

WHY DO THE LEAVES CHANGE THEIR COLOR IN AUTUMN?

Work completed:

Zhilinskaya Daria Sergeevna,

4th grade student

municipal treasury

general educational institution

"Kholmovskaya average

comprehensive school»

Bakhchisarai region

Republic of Crimea

Supervisor:

Kolesnikova Svetlana Nikolaevna,

primary school teacher

municipal treasury

educational institution

"Kholmovskaya average

comprehensive school"

Bakhchisarai region

Republic of Crimea

Simferopol - 2015

CONTENT

INTRODUCTION ______________________________________________________________3

LITERATURE REVIEW_____________________________________________5

1. Causes of discoloration of leaves in trees and shrubs ________5

   Scientists about changing the color of leaves _________________________________6

   Features of leaf fall in deciduous trees and shrubs _______7

RESEARCH METHODS AND RESULTS_____________________9

2.1. Evidence of the presence of chlorophyll pigment in the leaf _________________9

2.2. Evidence of the anthocyanin pigment in the leaf __________________9

2.3. Evidence of the presence of carotene and xanthophyll in the leaf ______________ 10

2.4. Obtaining watercolors from a solution of anthocyanin and chlorophyll ____11

CONCLUSIONS _______________________________________________________________12

LIST OF USED LITERATURE AND INTERNET SOURCES _________________________________________________________14

APPS

INTRODUCTION

"It's a sad time! Oh charm!

I like your sad beauty

I love the magnificent nature of wilting,

Forests clad in crimson and gold…”

/A.S.Pushkin/

We have always been interested to know where autumn has so many bright and varied colors. After all, in summer all the leaves are green. Why exactly in autumn the foliage changes color, and the leaves turn yellow, red, crimson. Last year, in the lesson "The world around us," we studied seasonal changes in nature. They brought a lot of colorful leaves from the excursion.We were interested in exploring:Why do leaves on trees turn different colors in autumn?

Objective: to study the reasons for changing the color of leaves in trees and shrubs before leaf fall.

To achieve this goal, the followingtasks:

1. Study the literature on the topic.

2. Conduct observations on the color of deciduous trees and shrubs in the autumn.

3. Explore why the leaves on trees and shrubs change color in autumn.

4. Do your researchon the isolation of coloring pigments from the leaf and find their application.

4. Find out why trees and shrubs shed their leaves for the winter.

5. Draw conclusions.

Object of study: fallen leaves of trees and shrubs.

Subject of study: discoloration of the leaves of trees and shrubs.

Hypothesis: I assume that the leaves change color on trees and shrubs because the tree is sick and the leaves are afraid of the cold.

Research methods. Analysis of scientific literature, experiments.

LITERATURE REVIEW

1. Causes of discoloration of leaves in trees and shrubs

Having studied the scientific literature, we found out that the leaves initially contain substances such as chlorophyll, xanthophyll, carotene, anthocyanins.

The green substance found in tree leaves is called chlorophyll. During the summer, chlorophyll and sunlight work together to help trees recycle their main food source, carbon dioxide. So sunlight and chlorophyll are the knife and fork that help trees absorb the air we exhale, which in turn helps trees grow big and strong. Chlorophyll is easily destroyed. But in the summer, under the influence of sunlight, it quickly recovers. When autumn comes and the light becomes less and less, chlorophyll is destroyed and does not have time to recover. The leaves get rid of the green pigment, and their true color appears for a while.
The substance xanthophylls gives the leaves a yellow color, carotene - orange. Bright red, crimson shades give the leaves anthocyanin pigments.
In summer, these pigments are not visible, we see only green chlorophyll. With the onset of cold weather, the nutrients collected in the leaves of trees enter the branches and trunk. Since the production of nutrients stops in winter, chlorophyll decomposes. With its disappearance, other pigments that were constantly present in the leaf become visible. And we enjoy the variety of tree colors.

1. Scientists on changing the color of leaves

Back in the 18th century Genevan pastor Jean Senebier thought about the question: why is this green world green? Having studied the action of sunlight, he showed that due to the process of oxygen formation and absorption carbon dioxide What happens in the green leaf feeds on the plant, and through it the animal world. This is how one of the greatest discoveries. But the question of the green color of the leaves remained open.[ 1; 7 ]

Natural scientists around the world were looking for an answer to it. The great Russian scientist Kliment Arkadyevich Timiryazev spent more than 35 years studying the green leaf, which stores the sun's rays for future use. The most important role of the pigment chlorophyll in the process of photosynthesis and the importance of plants on Earth were discovered.

And on the Internet, we found new facts on this issue.Professor of biology at the University of London, Imperial College Thomas Dering, in the course of research on the change in autumn leaf color, came to the conclusion that by doing so, plants are trying to protect themselves from a number of dangerous pests. Studying the colors that "prefer" insect pests, primarily aphids, the scientist found that they, when laying eggs in the fall, avoid the red range. At the same time, green and yellow colors cause preference among pests. Moreover, Dering found that with an increased concentration of pests, the leaves can turn red even in those trees that usually have yellow foliage in autumn. Traditionally, the color red in nature denotes danger. But scientists from the University of North Carolina at Charlotte, led by Emily Habink, found out that the whole thing is in the soil. If the soil is poor in nitrogen, the leaves will produce more red pigment. With its help, the foliage will last longer on the branches, and the tree will be able to take more useful substances from it. Thus, it will at least slightly compensate for the deficiency of nitrogen. But when the tree does not need such nourishment, then nature leaves the leaves yellow. Thanks to this discovery of scientists, it will now be possible to determine the quality of the soil by the color of the leaves. If in autumn the forest turned into beautiful red tones, it means that not everything is safe with the land in these places.[ 4 ]

Hence,there are other theories of scientists about the change in color of leaves in autumn. It's interesting to know!

1. Features of leaf fall in different trees and shrubs

One of the most characteristic phenomena of the arrival of autumn is leaf fall. Why do deciduous trees and shrubs shed their foliage every year? It is necessary to find out whether leaf fall is a biological phenomenon for deciduous trees and shrubs, or whether it is due to climate change. If a deciduous tree is transplanted into a warm room, it will shed its foliage despite good temperature conditions. That is, leaf fall is not a consequence of unfavorable conditions for trees and shrubs, but is a plant development cycle. It can be seen that there is a "leaf pad" at the point where the leaf is attached to the branch of the deciduous tree. When leaf fall begins, the leaves are easily separated from the tree and remain hanging on the vascular bundles that connect the leaf to the tree. They serve to supply substances from the root of a deciduous tree to the leaves. When this connection between the foliage and the tree is broken, the branches of the deciduous tree lose their finery.

Leaf fall is an adaptation of deciduous trees and shrubs to harsh conditions. If a deciduous tree remains in winter with green leaves, it will die from lack of moisture. The importance of leaf fall in the life of deciduous trees is especially noticeable when compared with conifers. Coniferous trees (especially pine and spruce) - tolerate drought well. In addition, the needles evaporate very little water than the foliage of deciduous trees. Therefore, coniferous trees can remain green all year round. The amount of moisture that conifers evaporate is ten times less than that of deciduous trees. But larch behaves like a deciduous tree and evaporates moisture 5 times more than spruce and 10 times more than pine. The ability of coniferous trees to save moisture is achieved through needles. The needles have many devices for retaining moisture: thick skin, wax coating. The leaves of deciduous trees lack drought-resistant adaptations.

In addition to the fact that deciduous trees are saved from drought due to leaf fall, in winter this saves them from felling. In winter, even bare branches of trees break under the weight of snow. What would happen if snow settled on the broad leaves of deciduous trees?

During leaf fall, deciduous trees get rid of excess mineral salts, which become harmful to trees and shrubs. With age, the ash content of the foliage of trees increases. The accumulation of minerals in deciduous trees occurs because the leaves of the tree evaporate a lot of water. It is replaced by new moisture, which contains minerals. Part of them goes to feed the deciduous tree, the rest remains in the leaves. Leaf fall for a deciduous tree is a normal condition for the normal growth and development of the plant. Coniferous trees do not need such shedding of needles, since pines, spruces and other conifers evaporate very little moisture. Larch, by evaporation of moisture, reaches the level of deciduous trees, therefore, in a humid climate, soft needles are shed. [4 ]

All these facts prove that leaf fall depends not only on external conditions, but is also necessary for the normal functioning of deciduous and coniferous trees and shrubs.

II. RESEARCH METHODS AND RESULTS

2.1. Evidence of the presence of chlorophyll pigment in the leaf

We place a green leaf in a test tube with alcohol and heat it over an alcohol lamp. After some time, the alcohol should turn green, and the sheet will be colorless.

Thus, the alcohol really turned green, and the leaf became colorless, this proves the presence of a green pigment in the leaf - chlorophyll.

2.2. Evidence of anthocyanin pigment in the leaf

There are several ways to verify the presence of anthocyanins in leaves.

First: you need to boil the red leaves and drop vinegar into this solution. The color of the solution will turn pink-red.

Second: grind red leaves in a mortar with a small amount of sand, and add 5 ml of water, filter.

Based on this,the color of the solution in the first and second experiments convinces that anthocyanins are water-soluble red pigments found in the leaves.

2.3. Evidence of the presence of carotene and xanthophyll in the leaf

I add 5 ml of ethyl alcohol to the crushed green leaves, chalk on the tip of a knife and grind in a porcelain mortar until smooth until the alcohol turns green. I put a drop of the resulting liquid on the paper with a glass rod.

In addition, after 3-5 minutes, colored concentric circles formed on the paper: green in the center, yellow-orange on the outside, which proves the presence in the leaf of a green pigment - chlorophyll, yellow pigment - xanthophyll, orange - carotene.

2.4. Obtaining watercolors from a solution of anthocyanins and chlorophyll.[ 1 ]

We decided to use the solutions obtained during the experiments to obtain paints. For this, solutions of anthocyanins and chlorophyll differing in color were prepared.by adding water. Pieces of gum (glue from tree trunks) were dissolved in a small volume of water. The gum solution was poured into paint molds. The resulting solutions were added to each form. Stirred. The colors are ready.

I painted a flower with these paints.

So, with the help of solutions obtained from autumn leaves different color, water and gums, you can prepare watercolors of various shades and use them in drawing.

CONCLUSIONS

The most remarkable sign of autumn: the change in color of the leaves.For example, who has not admired the colors of a flowering meadow, a forest edge, the gifts of a garden and a field? But not everyone knows where nature has such a rich palette of colors.

Why do leaves change color in autumn? Having studied the scientific literature, we found out that the leaves initially contain substances such as chlorophyll, xanthophyll, carotene, anthocyanins. Chlorophyll makes leaves green, xanthophyll yellow, anthocyanins red, and carotene orange. In autumn, chlorophyll is destroyed, and orange, yellow and red pigments are preserved and become noticeable.

After conducting research, we were convinced that the leaves do contain coloring pigments.And if they are contained there, then what does the soil or dangerous pests have to do with it?

Our first hypothesis that the trees get sick in autumn, and therefore change the color of the leaves, was not confirmed. But we realized that the autumn color of the leaves depends on what pigment, besides chlorophyll, is in the leaves.

After working with various sources, we learned that leaf fall is a natural fall of leaves from trees and shrubs, associated with preparation for winter.

Thus, our second hypothesis that the leaves are afraid of the cold and therefore fly around in autumn was also not confirmed. But we found out that it is beneficial for trees and shrubs to shed their leaves in order to survive in the cold winter.

So, the leaves initially contain various coloring substances. Chlorophyll makes leaves green, xanthophyll yellow, anthocyanins red, and carotene orange. In autumn, chlorophyll is destroyed, and orange, yellow and red pigments are preserved and become noticeable.

REFERENCES AND INTERNET SOURCES

1.Baturitskaya N.B., Fenchuk T.D. "Amazing experiments with plants", Mn., "Nar.asveta", 1991, p. 5-8, 14-16

2. Dietrich A. "Why", M. "Word", 1990, p.314

3. Encyclopedia "Heroes of Russian History", M., "White City", 2006, p.395

What dyes make leaves different colors.

Throughout the year, our planet plays various paints. And all thanks to the plants for which it is rich. And, probably, many people had such a question: why are the leaves of one color or another? Especially, it interests our children, who are so fond of asking questions. And in order to answer them correctly, you need to properly understand yourself.

What pigment colors leaves green or red?

In the school curriculum at the lesson of biology, a similar topic is required. Some may have already forgotten, and some just do not know yet. But the pigment that is responsible for the green color of the leaves is chlorophyll. Let's take a closer look at this aspect.

Leaf color green:

• Chlorophyll is a substance that absorbs sunlight and, with the help of water and carbon dioxide, produces useful organic substances for plants. Or, as they say in scientific language, transforms inorganic substances into organic.
• It is this pigment that is fundamental in the process of photosynthesis. Thanks to him, all living organisms receive oxygen. Yes, this information is known to any student. But few have thought about how chlorophyll turns leaves green.

• Yes, the element itself is also green. And since it prevails in plants, the color also depends on it. And you can draw a direct relationship between the color of foliage and the amount of chlorophyll.
• But that's not all. If you delve in more detail into a similar topic, you can find out much more. The fact is that chlorophyll absorbs the spectra of colors such as blue and red. This is the very reason why we see green leaves.

Leaves red:

• Based on the above reasons, you can find the answer to why the leaves are red. Even if you do not take into account the course of biology. From a logical point of view, the red color also, to some extent, depends on chlorophyll. Or rather, from his absence.
• The pigment responsible for the red color in the leaf is anthocyanin. Also, this element is responsible for the blue and purple color of leaves, flowers and fruits.

• Anthocyanin, like chlorophyll, absorbs certain color spectra. In this case, it's green.
• By the way, there are plants that do not have green leaves or flowers. It depends on the fact that they lack chlorophyll. And in its place is anthocyanin.

How do you explain the change in color of tree leaves in autumn?

What a beautiful autumn we have. Despite the rain and cloudy sky, it is beautiful in its own way. It is autumn that the trees are painted in different colors. Of course, it depends on the weather and the nature of the tree. But everyone paid attention that even on one sheet there can be several shades or colors.

• Previously, it was believed that all pigments are constantly present in the foliage. And when the amount of chlorophyll decreases, then other colors become visible. But this option is not entirely true. Specifically refers to anthocyanins.
• This pigment begins to appear in the leaves only after the level of chlorophyll begins to decline.
• Let's look at this process in more detail. In autumn, the sun is already not so warm, which means that there is less chlorophyll. Since it is he who is responsible for the nutrients in plants, their number is also reduced. So the leaves begin to prepare for the cold.
• This process is very subtle and thoughtful. All those useful material, which the plant has accumulated over the summer, slowly moves into the branches and root. There they will be all the cold time. And in the spring they will use this stock so that new green leaves appear.

• But the coloring of the leaves, in addition to natural processes, is also affected by the weather. Usually in sunny weather, anthocyanins predominate more. If the autumn is overcast and rainy, then there will be more yellow in the trees.
• But that's not all. The color of the leaves also depends on the breed of the plant itself. Everyone noticed that the maple often has reddish leaves, but the linden and birch always dress in a golden color.
• Just before winter, when all the coloring pigments are completely destroyed, the leaves become Brown. They no longer have any nutrients left, the leaves dry up and fall off. At this stage, the cell walls of the leaves become visible.

What substance turns foliage yellow: plant pigments

Yellow color is very beautiful in autumn, especially on a clear and warm day. It is not for nothing that autumn is called golden. Almost any plant changes its color, starting with yellow. Yes, for some it is the only color, and some have it only as an additional one.

• A specific pigment is responsible for each color. Carotene This pigment gives plants their yellow color. The word is familiar and can often be heard in advertising. Perhaps many did not know its meaning. Or they just didn't even know what it was.
• This pigment belongs to the group of carotenoids. Found in all leaves and plants. Stays in them all the time. It's just that chlorophyll prevails over carotene, so the leaves are mostly green. And after its collapse, they begin to be painted in other colors.

• This plant pigment is used as a natural dye. It is mined chemically, but exclusively from natural raw materials. It is widely applied in the food industry and other fields.
• beta-carotene, which just overshadowed the advertising business, also apply to carotenoids. The fact is that there are about 600 subspecies of them. Almost all yellow, red, orange and even green vegetables and fruits have it. For example, green onions, tomatoes, pumpkins, persimmons, blueberries, sorrel, carrots. The list is very long. It is also very important for the human body.

What substance colors foliage orange: plant pigments

Orange, like yellow, is constantly in the leaves, it's just overshadowed by chlorophyll. Thus, making the plants green. And the orange color also begins to appear when that same chlorophyll is destroyed.

• The pigment responsible for the orange color is xanthophyll. It also belongs to the class of carotenoids, like carotene. After all, these colors are on fine line between themselves.
• I would like to note that carrots color this particular pigment. It contains the most of it. Therefore, it is this pigment that is responsible for the orange color of all fruits and the color.
• Xanthophylls, like other carotenoids, are necessary for the human body. Other living beings too. Since they cannot synthesize it on their own, but can only get it with food.

• It is no secret that carrots are rich in vitamin A. Accordingly, all these pigments are the main carriers of this vitamin. More precisely, the predecessors.
• It is also worth noting that they are antioxidants in our body. Every girl knows about this aspect. After all, it directly depends appearance hair, nails and the body as a whole.

The strongest orange natural dyes

Each housewife faced such a problem in the kitchen when, after, for example, beets, her hands turned red. If you rub carrots a lot, then the same story can happen. It's just that the color is not as saturated, so it's not as noticeable. Also, by picking a certain flower, you can paint your hands in the appropriate color.

• Natural dyes are widely used in cooking, for dyeing fabrics, in medicine and cosmetology.
• Coloring pigments are produced by bacteria, corals, fungi, algae and plants. Naturally, the corresponding color. Of course, plants are the most accessible.
• You can get them yourself, the main thing is to follow the technology. And you also need to know which ingredients are suitable for these purposes.

• carrot
• celandine leaves and flowers
• tangerine and orange zest
• paprika
• onion peel
• pumpkin

As you can see, all products are available and almost all are orange in color. You can also get such a dye by mixing yellow and red.

The leaves of which group of trees turn red in autumn?

Probably, many have noticed that not all trees are red in autumn. But what is the beauty of nature. Especially in combination with yellow and orange flowers. One gets the impression that the forest is shrouded in festive attire. But what kind of trees have exactly a red tint? Let's look at this issue in more detail.

• This color is not permanent in the leaves, but begins to be produced only after the breakdown of chlorophyll.
• Usually, those trees that grow on poor, unmineralized soil turn red.
• An interesting fact is that trees use this color to repel insects and pests.
• Anthocyanin, the presence of which stains the foliage red, helps to endure frosts and avoid hypothermia.
• More common in trees such as maple, rowan, bird cherry and aspen

Changing the color of trees is a real miracle of nature, which is so pleasant to watch. Please yourself with pleasant emotions in the fall, because these are unforgettable pleasant sensations.

Video: Why do leaves change color?

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 rich 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 tints of color and 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 the winter season is the lack of moisture, so in the fall all useful substances begin to accumulate in the roots and core, and the leaves fall off. Leaf fall helps not only to increase moisture reserves, but also to save them. The fact is that 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 not so much associated with the change of seasons and preparation for winter, but is an important part of the life cycle of 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 converts light into nutrients and gives the foliage a 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 weather conditions. If the weather is sunny and relatively warm outside, then autumn leaves will be bright and colorful, and if it often rains, 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?

Leaves play an important 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 the evaporation from their surface of much-needed moisture in winter. 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 severe frosts. The air that the needles capture creates a kind of insulating layer around the tree.

The only coniferous plant that leaves its needles for the winter is larch. It appeared in ancient times, when summers were very hot and winters were incredibly frosty. 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 conditions and retain 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 the jasmine gardenia. Her homeland is China.

Autumn is one of the most beautiful and colorful seasons. Flashes of purple and golden leaves, preparing to cover the ground with a multi-colored carpet, coniferous trees piercing the first snow with their thin needles and evergreens, always pleasing to the eye, make the autumn world even more delightful and unforgettable. Nature is gradually preparing for winter and does not even suspect how fascinating these preparations are to the eye.

Deciduous forests and orchards change color in autumn. In place of the monotonous summer coloring, a wide variety of bright colors appears.

The leaves of hornbeams, maples and birches become light yellow, oaks become brownish-yellow, cherries, mountain ash and barberry turn crimson red, bird cherry - purple, privet and euonymus - purple, aspen - orange, alder - a cloudy brown-green hue.

The autumn color change of the leaves is not limited, however, only to trees and shrubs, but also extends to stunted grasses. The foliage of small herbs and shrubs, and especially dwarf shrubs, forming shaggy carpets, acquires red, purple and yellow tones with all transitional shades, not inferior in brightness to live flowers.

The change in color is explained by profound changes in the vital activity of leaf tissues with the approach of unfavorable winter time. In spring and summer, chloroplasts are more or less evenly distributed in the wall layer of protoplasm. This causes the bright green color of the leaves. With the onset of autumn cold weather, chloroplasts crowd into compact clumps, and, according to some scientists, the protoplasm separates from the cell walls. This leads to a change in the bright green color of the leaves to dark and dull. Such seasonal changes in the color of the needles are clearly observed in our evergreen conifers: spruce, pine, juniper, etc.

In the vast majority of trees and shrubs of the cold and temperate zone, adaptation to winter with its frosts has gone in the direction of the formation of deciduous forms that shed their leaves for the winter. The autumn coloring of deciduous species is a consequence of the death of foliage associated with this season. In the leaves, along with the green pigment - chlorophyll, there are always yellow pigments - xanthophyll, carotene and others, which are invisible behind chlorophyll, as having greater brightness. In autumn, in deciduous species, in the process of preparing foliage for fall, chlorophyll is destroyed, and yellow pigments, previously masked by chlorophyll, become visible. In this case, the yellow pigments are not chemically changed.

The situation is different with red, blue and other autumn colors of foliage. Here, the destruction of chlorophyll proceeds in the usual way, but here the formation of a new coloring pigment, anthocyanin, is also added.

The change in color of the leaves is followed by their fall - autumn leaf fall. Leaf fall is one of the most important adaptations against unfavorable winter conditions for the plant.

Leaf fall is characteristic of all trees and shrubs and follows from the growth characteristics of this group of plants. Older leaves become more and more shaded as the crown grows. The possibility of their assimilation falls more and more. Old leaves gradually die off and fall off. In a humid tropical climate, this change of leaves occurs gradually, not being timed to a specific time of the year. Each leaf is often able to live and assimilate for several years. The trees and shrubs of the humid tropics are usually evergreen. In our northern climate, trees live and develop during the annual change of summer and harsh winter. Under these conditions, natural selection has developed a strict seasonal periodicity in the timing of leaf fall, with the annual dropping of all foliage once a year - in autumn. Thus, leaf fall arose. The main significance of autumn leaf fall is that, by losing leaves, plants are thereby saved from drying out, which would lead to inevitable death. The leaves represent a huge evaporation surface for the moisture contained in the plant. In the warm season, this loss of moisture is replenished evenly by its influx from the soil, from where it is absorbed by the roots. But with the cooling of the soil, the absorption activity of the root hairs decreases; it decreases so much that although the evaporation of moisture from the leaves also decreases due to the low temperature, nevertheless, the loss of water by the plant can no longer be compensated.

Water from the roots to the crowns of trees can also move at temperatures below zero. But already at –6, – 7°, the speed of this movement and the amount of water sucked in become negligible. With a further decrease in temperature, the branches freeze completely, the water flow completely stops, and the loss of shoots in moisture from evaporation (more precisely, ice sublimation) ceases to be replenished. The significance of autumn leaf fall, first of all, consists in a sharp reduction in the evaporating surface for the winter, and, consequently, in the loss of water by the plant.

By shedding leaves, plants lose a lot of the organic matter created during the summer. However, the most valuable of them are removed, as we have seen, from the leaves into the internal parts of the plant.

Not only such reserve nutrients as starch, sugar, fats (oils) leave the leaves, but also the most important ones - protein substances - having previously decomposed into simpler soluble substances. Even the most valuable mineral substances (for example, phosphorus compounds), as shown by a chemical analysis of the leaves made before leaf fall, are taken out of the leaves. But along with this, some unsuitable products are also removed. So, by the end of summer, a large number of crystals of oxalic acid lime accumulate in the leaves. This substance is a waste product of metabolism. In view of this, autumn leaf fall can also be viewed as the excretory function of a plant, which takes place once a year, but on a grandiose scale.

There is another direction of adaptations that led to deciduousness - adaptation to the transfer of the sultry-dry season. This type of deciduousness acquires the highest development in the tropics - in the savannahs. But even within the CIS in the zones of deserts and semi-deserts, summer leaf fall at the beginning of the hot-dry period is of great importance. Summer leaf fall is also observed in many semi-shrubs, for example, in wormwood and a number of saltworts. In autumn, in the presence of rain, leaf formation in these plants resumes. The biological significance of summer leaf fall is the same as that of autumn - protecting the plant from drying out.

The mechanism of leaf fall is as follows. Before the leaves fall, layers of special thin-walled cells appear at the base of their petioles. These are the so-called separating layers. Due to the rapid multiplication of these cells from the outside, a swelling appears against the separating layer, which differs from coarse old tissues in a lighter color and some transparency. When the separating layers have reached the appropriate thickness, their thin-walled cells are separated from one another, and the membranes are not torn or damaged anywhere. In all likelihood, the intercellular substance connecting them is dissolved by organic acids, due to which the connection between the cells is broken and the leaves fall off. This happens even by itself, in the absence of external incentives.

The separating layer is sometimes formed not in the lower part of the petiole, but is located in such a way that a small scaly residue remains from the petiole, which serves as a protection for the bud developing in its sinus, for example, in jasmine. In complex leaves, a separating layer, in addition to the base of the main petiole, appears even below each leaflet. The surface at the place of separation of the petiole is covered with a cork layer and is always smooth and of a certain shape for each plant species.

The cells that form the separation layer require a certain temperature to multiply. external environment. Early and sudden frosts in some years can prevent the appearance of separating layers, and the leaves then freeze before they fall off. In such years, dry, browned leaves remain on many trees throughout the winter.

The time of appearance of the separation layer turns out to be dependent on the length of the daylight period: the shorter it is, the sooner the separation layer appears. Thus, the shortening of the day towards autumn is one of the factors stimulating the shedding of leaves.

By means of a change in tissues similar to the one described, flower petals, stamens, the flowers themselves, which remained unpollinated, ripe fruits, leaf petioles, if the plates are torn off from them, etc., are also sometimes separated. Therefore, leaf fall is only a special case from a number of homogeneous phenomena.

Fall duration various trees is not the same. So, in ginkgo, leaf fall lasts only a few days, and in hornbeams and oaks - several weeks, and in the fall only part of the leaves fall off these trees, and the rest fall off only at the end of winter. There is a difference in the following respect. In some trees, the extreme branches begin to be exposed from the leaves, and from here the leaf fall gradually reaches the base; in others it has the opposite direction. An example of the first order is ash, hazel and beeches, and the second - lindens, willows, poplars, pears.

9. Influence of abiotic factors on the growth and development of plants

Temperature

Features of the development of plants in phylogeny evolved over many millennia under the constant influence of environmental factors. characteristic feature The climate of the temperate zone is the presence of a cold period of the year, interrupting the vegetation of plants. In most plants whose biological properties have developed under temperate climates, the lower temperature limit for development is close to 5°. The relationship between the rate of development of these plants and air temperature can be expressed by the equation: n(t - 5°) = A, where P - the number of days in a given period, t- average temperature air during this period. the value (t- 5°) is called the average effective temperature for the period, 5° is the lower limit of the effective temperature for plants of a temperate climate, A - the sum of effective temperatures for the period or the sum of the differences between the average daily temperature and zero effective temperature.

The sums of effective temperatures for a given period are calculated as follows: for each day of the period, the average daily air temperatures are written out and 5 ° are subtracted from each of their values, and the resulting differences are summarized.

The level at which the initial temperature of plant development is located depends on the conditions in which their biological characteristics developed over a very long period of evolution of plant forms under the influence of changes in the thermal conditions of existence. Thus, the lower limits of effective temperature in plants that have developed in tropical and subtropical climates are at a relatively high level: tomato - 15 °, citrus plants and rice -10°, cotton - about 13°, etc.

The acceleration of the rate of plant development with an increase in temperature has its limit. At a certain temperature, having reached the highest rate of development, the plant retains this rate, despite a further increase in the thermal stress of the environment. For example, at an average daily temperature of 18° for winter rye, the period from sowing seeds to germination reaches four days, and for winter and spring wheat - 5 days. At temperatures above 18°, the duration of this period no longer decreases.

In the presence of the necessary conditions for growth, the onset of the early phases of development of herbaceous plants occurs depending on the temperature of the environment. After the end of the light stage and the initiation of the embryonic inflorescence, the duration of the entire reproductive period and its parts depends only on temperature. Ear formation in winter crops depends on the preservation of leaves and stem shoots after overwintering. With the preservation of the leaves and the main stem shoots, the formation of an ear (exit to the tube) begins shortly after the resumption of vegetation.

Table 5. The values ​​of the sums of effective temperatures for cereals

The rate of development affects the productivity of plants. With an increase in the duration of the period from heading to wax ripeness of cereals, grain size and weight increase. So, with the duration of this period in spring wheat, some other varieties of soft wheat in 23 days, 1000 grains in an air-dry state weigh about 23 g, and with a duration of 50 days - about 50 g.

Using the sums of effective temperatures as indicators of the relationship between the rate of plant development and temperature, one can judge the duration of the most important interphase periods, determine the course of plant development, both for the past and future periods, and make other calculations.

Trees and shrubs

In most of the territory of Russia, deciduous woody plants that have arisen in temperate climates begin to vegetate long after the end of the period of deep dormancy. In the first days, when the air temperature passes through 5 0, swelling of the kidneys begins. Since the development of the organs laid down in the kidneys occurs due to the reserve substances accumulated in the previous year, the growth rate of the vegetative organs in the spring and the development of the flowering organs depend on the ambient temperature.

Table 6. The values ​​of the sums of effective temperatures

for woody plants

That is why the sums of effective temperatures, accumulated by the time of flowering or unfolding of the first leaves in each tree species, remain very constant, as in a given area in different years, and in different physical and geographical conditions.

Plant types (botanical systems)
and types of influence of temperature on plant development

Fanerophytes are tall plants, trees and shrubs, the resting buds of which on the shoots are high above the surface of the soil and snow cover. The beginning of their vegetation in the spring depends, first of all, on the air temperature. Such plants include birch, oak, pine, etc.

Hamefites, or dwarf plants and shrubs, whose dormant buds are above the soil surface, but winter under the snow (for example, blueberries, lingonberries, heather).

Hemicryptophytes. Buds hibernate under snow cover and dead parts of plants (for example, winter cereals, strawberries, rhubarb, snapdragons, primrose, etc.). The beginning of the growing season is associated with the melting of the snow cover and an increase in the temperature of the surface layers of air.

Cryptophytes are perennials. Buds overwinter in the soil in bulbs and tubers.

Terophytes are annuals that overwinter as seeds. These include the majority cultivated plants. Cryptophytes and terophytes begin to germinate with sufficient warming of the upper layers of the soil.

Seasonal weather changes influence individual stages of development. So, in early-flowering trees and shrubs flower buds are laid in the previous summer, the weather conditions of which affect their development. The development of plants that bloom in spring depends mainly on the temperature of the period preceding flowering. It is quite possible to apply the rule of the sum of temperatures to them. For summer flowering, in addition to the sum of temperatures, the distribution of air humidity is important. The supply of nutrients in plants is also of great importance. Woody and bulbous plants containing significant food reserves are less affected by external conditions.

Only taking into account the botanical characteristics of plants, it is possible to resolve the issue of the relationship of temperature and other climatic conditions with the growth and development of plants.

Sunlight is a source of energy for the plant in the synthesis of organic substances. A prerequisite for this is the presence of a certain temperature. Intense radiation under the same temperature conditions enhances synthesis and accelerates development. In areas that differ in the duration and intensity of sunshine, accelerated development of plants is observed.

For radiation, as well as for temperature, you can calculate the total value for certain periods of plant development.

Geslin studied the influence of solar radiation on the development of plants in connection with temperature. He introduced the concept of the heliothermal constant, which is a function of temperature and radiation. With a lack of data on measuring radiation, he used the length of the day as an indicator of radiation. Such a connection of radiation with temperature in the study of the processes of plant development gives better results than the influence of sums of temperatures or sums of radiation taken separately.

Of great importance for organisms is not only the intensity of solar radiation, but also the duration of the length of the light period. The reaction of organisms to seasonal changes in day length is called photoperiodism (the term was proposed in 1920 by W. Garner and H. Allard). The manifestation of photoperiodism does not depend on the intensity of illumination, but only on the rhythm of the alternation of the dark and light periods of the day.

The photoperiodic reaction of living organisms is of great adaptive importance, since it takes quite a long time to prepare for experiencing adverse conditions or, conversely, for the most intense life activity. The ability to respond to changes in the length of the day ensures early physiological adjustments and the adaptation of the cycle to seasonal changes in conditions. The rhythm of day and night acts as a signal of upcoming changes in climatic factors that have a strong direct effect on a living organism (temperature, humidity, etc.). Unlike others environmental factors the rhythm of lighting affects only those features of the physiology and morphology of organisms that are seasonal adaptations in their life cycle. Figuratively speaking, photoperiodism is the body's reaction to the future.

Although photoperiodism occurs in all major taxonomic groups, it is by no means characteristic of all species. There are many species with a neutral photoperiodic response, in which physiological rearrangements in the developmental cycle do not depend on the length of the day. Such species either have developed other ways of regulating the life cycle (for example, wintering in plants), or they do not need precise regulation of it. For example, where there are no pronounced seasonal changes, most species do not exhibit photoperiodism. Flowering, fruiting and death of leaves in many tropical trees are extended in time, and flowers and fruits are found on the tree at the same time. In a temperate climate, species that have time to quickly complete their life cycle and are practically not found in an active state in unfavorable seasons of the year also do not show photoperiodic reactions, for example, many ephemeral plants.

There are two types of photoperiodic reaction: short-day and long-day. It is known that the length of daylight, except for the time of year, depends on geographical location terrain. Short-day species live and grow mainly in low latitudes, while long-day species live and grow in temperate and high latitudes. In species with extensive ranges, northern individuals may differ in type of photoperiodism from southern ones. Thus, the type of photoperiodism is an ecological rather than a systematic feature of the species.

In long-day species, increasing spring and early summer days stimulate growth processes and preparation for reproduction. The shortening days of the second half of summer and autumn cause growth inhibition and preparation for winter. Thus, the frost resistance of clover and alfalfa is much higher when plants are grown on a short day than on a long one. Trees growing in cities near street lamps have a longer autumn day, as a result, their leaf fall is delayed, and they are more likely to get frostbite.

As studies have shown, short-day plants are especially sensitive to the photoperiod, since the length of the day in their homeland changes little during the year, and seasonal climatic changes can be very significant. Photoperiodic species prepare tropical species for dry and rainy seasons. Some varieties of rice in Sri Lanka, where the total annual change in the length of the day is no more than an hour, capture even the slightest difference in the light rhythm, which determines the time of their flowering.

The length of the daylight period, which ensures the transition to the next phase of development, is called the critical day length for this phase. As the geographic latitude increases, the critical day length increases (Table 7). The critical length of the day often serves as an obstacle to the latitudinal movement of organisms and their introduction.

Table 7. Dependence of the critical day length

from geographic latitude

Geographic latitude	Oat seedlings	winter rye bloom
48 0	12.46	15.27
54 0	14.26	16.45

Photoperiodism is a hereditarily fixed, genetically determined property. However, the photoperiodic reaction manifests itself only under a certain influence of other environmental factors, for example, in a certain temperature range. Under a certain combination of ecological conditions, natural dispersal of species to latitudes unusual for them is possible, despite the type of photoperiodism. So, in the high-mountainous tropical regions there are many plants of a long day, natives of temperate climates.

For practical purposes, the length of daylight hours is changed when growing crops indoors. The average long-term periods of development of organisms are determined, first of all, by the climate of the area, and it is to them that the reactions of photoperiodism are adapted. Deviations from these dates are subject to weather conditions. When weather conditions change, the timing of the passage of individual phases may change within certain limits. Thus, plants that have not reached the required amount of effective temperatures cannot bloom even under photoperiod conditions that stimulate the transition to the generative state. For example, in the Moscow region, birch blooms on average on May 8 with the accumulation of the sum of effective temperatures of 75 ° C. However, in annual deviations, the timing of its flowering varies from April 19 to May 28.

The effect of light on a plant is subdivided into photosynthetic, regulatory-photomorphogenetic, and thermal. Light affects growth through photosynthesis, which requires high levels of energy. Plants do not grow well in low light. However, short-term growth occurs even in the dark, for example, during germination, which has an adaptive value. Extending the daily light in greenhouses enhances the growth of many plants. In relation to the intensity of illumination, plants are divided into light-loving and shade-tolerant.

Light determines not only photoperiodism, but also many other photobiological phenomena: photomorphogenesis, phototaxis, phototropism, photonasts, etc. Red and blue-violet rays most actively regulate growth.

Photomorphogenesis is the light-dependent processes of plant growth and differentiation that determine its shape and structure. During photomorphogenesis, the plant acquires the optimal shape for absorbing light under specific growing conditions. So, in intense light, stem growth decreases. In the shade, the leaves grow larger than in the light, which proves the retarding effect of light on growth. In plants, two pigment systems of photoreceptors, phytochrome, which absorbs red light, and cryptochrome, which absorbs blue light, were found, with the participation of which reactions of photomorphogenesis are induced. These pigments absorb a tiny fraction of the incident solar radiation, which is used to switch metabolic pathways.

Red/high red light system. Photomorphogeneti-
The physical effect of red light on the plant is carried out through phytochrome. Phytochrome is a chromoprotein that has a blue-green color. Its chromophore is an open tetrapyrrole. The protein part of phytochrome consists of two subunits. Phytochrome exists in plants in two forms (F 660 and F 730), which can pass one into another, changing their physiological activity. When irradiated with red light (KS - 660 nm), phytochrome F 660 (or F c) passes into the form F 730 (or F dc). Transformation leads to reversible changes in the chromophore configuration and protein surface. The F 730 form is physiologically active, controls many reactions and morphogenetic processes in a growing plant, metabolic rates, enzyme activity, growth movements, growth and differentiation rates, etc. The action of red light is removed by a short flash of far red light (FRL - 730 nm). Irradiation with FRL converts the phytochrome into an inactive (dark) form F 660 . The active form F 730 is unstable and slowly decomposes in white light. In the dark, Fc is destroyed or, under the action of far red light, turns into Fc. Thus, the system

constitutes a complex of reactions triggered by the transition from dark
you to the world. Plant metabolism reactions controlled by phytochrome depend on the F 730 concentration and the F 730 /F 660 ratio. They usually begin if 50% of the phytochrome is in the F 730 form.

Phytochrome is found in the cells of all organs, although it is more abundant in meristematic tissues. In cells, phytochrome is apparently associated with the plasmalemma and other membranes.

Phytochrome is involved in the regulation of many aspects of plant life: germination of light-sensitive seeds, opening of the hook and elongation of the hypocotyl of seedlings, deployment of cotyledons, differentiation of the epidermis and stomata, differentiation of tissues and organs, orientation in the cell of chloroplasts, synthesis of anthocyanin and chlorophyll. Red light inhibits division and promotes cell elongation, plants stretch out, become thin-stemmed (dense forest, thickened crops). Phytochrome determines the photoperiodic response of plants, regulates the onset of flowering, leaf fall, aging and transition to dormancy. In greenhouses, red light promotes the formation of root crops in turnips, thickening of kohlrabi stem crops. Phytochrome is involved in the regulation of phytohormone metabolism in various plant organs.

Effect of blue light on plant growth. Blue light also regulates many photomorphogenetic and metabolic reactions in plants. Blue light photoreceptors are flavins and carotenoids. The yellow pigment riboflavin, which receptors for blue-near ultraviolet light, called cryptochrome, is present in all plants. In the ultraviolet part of the spectrum (320–390 nm), one more receptor system probably operates, including pyrazinopyrimidine derivatives, or pterins. Receptors undergo redox transformations, rapidly donating electrons to other acceptors. Plant phototropism is determined by the receptor complex of the stem apex, which apparently includes cryptochrome and carotenoids. Blue light receptors are present in the cells of all tissues, localized in the plasmalemma and other membranes.

Blue and violet rays stimulate cell division but delay cell elongation. For this reason, the plants of high-mountainous alpine meadows are usually undersized, often rosettes. Blue light induces phototropic bending of the seedling and other plant axial organs by inducing lateral auxin transport. Plants in deficiency of blue color in thickened crops and plantings they stretch out and lie down. This phenomenon takes place in thickened crops and plantings, in greenhouses, the glass of which blocks blue and blue-violet rays. Additional illumination with blue light allows you to get a high yield of lettuce leaves, radish roots in greenhouses. Blue light also affects many other processes: it inhibits seed germination, stomata opening, the movement of the cytoplasm and chloroplasts, leaf development, etc. Ultraviolet rays usually retard growth, but in small doses they can stimulate it. Hard ultraviolet light (shorter than 300 nm) has a mutagenic and even deadly effect, which is important in connection with the thinning of the Earth's ozone layer.

The mechanism of action of photoreceptors. Several hypotheses of the mechanism of the regulatory effect of light on plants have been proposed.

Direct action on the genetic apparatus. Photoreceptors, when excited by light, directly act on the genetic apparatus of plants, facilitating the biosynthesis of the necessary proteins. For example, in the nucleus and chloroplast, phytochrome regulates the synthesis of the small and large subunits of RDP carboxylase, respectively. In the nuclear genome, blue light accelerates gene expression of the nitrate reductase enzyme complex.

Regulation of the level and activity of phytohormones. Taking into account that phytohormones are one of the links of the metabolic chain closest to phytochrome, which ensures plant growth and morphogenesis, the following sequence of chain elements is assumed: light –> phytochrome –> genome -> phytohormones –> common metabolic links
ma –> growth and morphogenesis. In most cases, the COP, increasing in
tissues, the level of gibberellins and cytokinins, reduces the content of auxin and ethylene. This action of the red light removes the DCS. In the leaves of wheat and barley, CS increases the level of gibberellins as a result of their synthesis or release from etioplasts. The DCS eliminates this defect in the CS.

Influence on the functional activity of membranes. The main result of the action of red light is the regulation of membrane functions. Under the influence of light, the electrical characteristics of cell membranes and tissues of irradiated plant organs change most rapidly, which, apparently, causes a certain physiological effect, including the formation of phytohormones and the activation of some genes.

Direct effect of light on enzyme activity. It manifests itself in the fact that the pigment molecule, which is part of the enzyme, is excited by a quantum of light, causing a change in the conformation of the protein part of the enzyme, and, consequently, its activity.

Initiation of electron transfer processes. Light turns on photoreceptors and initiates processes of metabolic transfer of electrons in membranes, which are closely related to the movement of protons. Further, compounds are formed that lead to the final physiological response - the effect on the growth and morphogenesis of plants. The electrons formed during the oxidation of the substrate can be used in reduction reactions, including those of nitrates, while the protons acidify the cell wall or remain in the cell.

End of work -

This topic belongs to:

Lectures on plant physiology

Moscow State Regional University.. da klimachev.. lectures on plant physiology Moscow klimachev da..

If you need additional material on this topic, or you did not find what you were looking for, we recommend using the search in our database of works:

What will we do with the received material:

If this material turned out to be useful for you, you can save it to your page on social networks:

tweet

All topics in this section:

MOSCOW - 2006
Published by decision of the Department of Botany with the basics of agriculture. Klimachev D.A. Lectures on plant physiology. M.: MGOU Publishing House, 2006. - 282 p.

And main lines of research
In the biosphere, the dominant position is occupied by the plant world, the basis of life on our planet. The plant has a unique property - the ability to accumulate the energy of light in organic matter.

The nature and functions of the main chemical components of the plant cell
The earth's crust and atmosphere contains more than a hundred chemical elements. Of all these elements, only a limited number have been selected in the course of evolution to form a complex, highly organized

Elemental composition of plants
Nitrogen - is a part of proteins, nucleic acids, phospholipids, porphyrins‚ cytochromes, coenzymes (NAD, NADP). Enters plants in the form of NO3-, NO2

Carbohydrates
Carbohydrates are complex organic compounds whose molecules are built from atoms of three chemical elements: carbon, oxygen, hydrogen. Carbohydrates are the main source of energy for living systems. Cr

plant pigments
Pigments are high-molecular natural colored compounds. Of the several hundred pigments that exist in nature, the most important from a biological point of view are metalloporphyrins and flavins.

Phytohormones
It is known that the life of animals is controlled by the nervous system and hormones, but not everyone knows that the life of plants is also controlled by hormones, which are called phytohormones. They regulate the

Phytoalexins
Phytoalexins are low molecular weight antibiotic substances of higher plants that occur in the plant in response to contact with phytopathogens; when rapidly reaching antimicrobial concentrations, they can

Cell wall
The cell membrane gives mechanical strength to plant cells and tissues, protects the protoplasmic membrane from destruction under the influence of hydrostatic pressure developed inside the cell.

Vacuole
Vacuole - a cavity filled with cell sap and surrounded by a membrane (tonoplast). A young cell usually has several small vacuoles (pro-vacuoles). As the cell grows, it produces

plastids
There are three types of plastids: chloroplasts are green, chromoplasts are orange, and leukoplasts are colorless. The size of chloroplasts ranges from 4 to 10 microns. The number of chloroplasts is usually

Organs, tissues and functional systems of higher plants
The main feature of living organisms is that they are open systems‚ which exchange with the environment energy‚ matter and and

Regulation of enzyme activity
Isosteric regulation of enzyme activity is carried out at the level of their catalytic centers. The reactivity and direction of the work of the catalytic center primarily depend on the

Genetic regulation system
Genetic regulation includes regulation at the level of replication, transcription, processing, and translation. The molecular mechanisms of regulation are the same here (pH‚ nones, modification of molecules, proteins-regulators

Membrane regulation
Membrane regulation occurs through shifts in membrane transport, binding or release of enzymes and regulatory proteins, and by altering the activity of membrane enzymes. All fun

Trophic regulation
Interaction with the help of nutrients is the simplest way of communication between cells, tissues and organs. In plants, roots and other heterotrophic organs depend on the intake of assimilates‚ o

Electrophysiological regulation
Plants, unlike animals, do not have a nervous system. However, the electrophysiological interactions of cells, tissues, and organs play an essential role in the coordination of functional

Auxins
Some of the earliest experiments on growth regulation in plants were carried out by Charles Darwin and his son Francis and are set forth in The Power of Movement in Plants, published in 1881 by Darwin.

Cytokinins
Substances necessary for the induction of plant cell division are called cytokinins. For the first time, pure cell division factor has been isolated from an autoclaved sample of sperm DNA.

Gibberellins
The Japanese researcher E. Kurosawa in 1926 found that the culture liquid of the phytopathogenic fungus Gibberella fujikuroi contains Chemical substance, contributing to a strong stretching of the stem

Abscisins
In 1961, V. Lew and H. Carnes isolated a substance in crystalline form from dry mature cotton bolls, which accelerates leaf fall, and called it abscisin (from the English abscission - separation, opa

Brassinosteroids
For the first time in the pollen of rapeseed and alder, substances with growth-regulating activity and called brassins were found. In 1979, the active principle (brassinolide) was isolated and its chemistry determined.

Thermodynamic foundations of plant water metabolism
The introduction of the concepts of thermodynamics into plant physiology made it possible to mathematically describe and explain the causes that cause both cell water exchange and water transport in the soil-plant-a system.

Absorption and movement of water
The soil is the source of water for plants. The amount of water available to a plant is determined by its state in the soil. Forms of soil moisture: 1. Gravitational water - fills

transpiration
The basis of water consumption by a plant organism is the physical process of evaporation - the transition of water from a liquid state to a vapor state, which occurs as a result of contact between plant organs.

Physiology of stomatal movements
The degree of opening of the stomata depends on the intensity of light, the water content of the leaf tissues, the concentration of CO2 in the intercellular spaces, air temperature, and other factors. Depending on the factor,

Ways to reduce the intensity of transpiration
A promising way to reduce the level of transpiration is the use of antitranspirants. According to the mechanism of action, they can be divided into two groups: substances that cause the stomata to close; thing

History of photosynthesis
In the old days, the doctor had to know botany, because many medicines were prepared from plants. It is not surprising that doctors often grew plants, conducted various experiments with them.

The leaf as an organ of photosynthesis
In the process of plant evolution, a specialized organ of photosynthesis, the leaf, was formed. Its adaptation to photosynthesis proceeded in two directions: perhaps more complete absorption and storage of radiant

Chloroplasts and photosynthetic pigments
The leaf of a plant is an organ that provides the conditions for the photosynthetic process to proceed. Functionally, photosynthesis is confined to specialized organelles - chloroplasts. higher chloroplasts

chlorophylls
Several are currently known various forms chlorophyll, which are denoted by Latin letters. Chloroplasts of higher plants contain chlorophyll a and chlorophyll b. They were identified by the Russian

Carotenoids
Carotenoids are fat-soluble pigments that are yellow, orange, and red. They are part of the chloroplasts and chromoplasts of non-green parts of plants (flowers, fruits, root crops). In green l

Organization and functioning of pigment systems
Chloroplast pigments are combined into functional complexes - pigment systems in which the reaction center - chlorophyll a, which performs photosensitization, is associated with energy transfer processes with

Cyclic and non-cyclic photosynthetic phosphorylation
Photosynthetic phosphorylation, i.e., the formation of ATP in chloroplasts during reactions activated by light, can be carried out in cyclic and non-cyclic ways. Cyclic photophospho

Dark phase of photosynthesis
Light phase products ATP photosynthesis and NADP. H2 is used in the dark phase to restore CO2 to carbohydrate levels. Recovery reactions take place

C4 pathway of photosynthesis
The path of assimilation of CO2, established by M. Calvin, is the main one. But there is a large group of plants, including more than 500 species of angiosperms, in which the primary products are fixed

CAM metabolism
The Hatch and Slack cycle was also found in succulent plants (from the genera Crassula, Bryophyllum, etc.). But if in C4 plants cooperation is achieved due to the spatial separation of two qi

photorespiration
Photorespiration is the light-induced uptake of oxygen and release of CO2, which is observed only in plant cells containing chloroplasts. The chemistry of this process is

Saprotrophs
At present, fungi are classified as an independent kingdom, but many aspects of the physiology of fungi are close to plant physiology. Apparently, similar mechanisms underlie their heterotrophic

carnivorous plants
Currently, over 400 species of angiosperms are known that catch small insects and other organisms, digest their prey and use its decomposition products as an additional

glycolysis
Glycolysis is the process of generating energy in the cell, occurring without the absorption of O2 and the release of CO2. Therefore, its speed is difficult to measure. The main function of glycolysis along with

Electron transport chain
In the considered reactions of the Krebs cycle and in glycolysis, molecular oxygen does not participate. The need for oxygen arises from the oxidation of reduced carriers NADH2 and FADH2

Oxidative phosphorylation
Main Feature The inner membrane of the mitochondria is the presence in it of proteins - electron carriers. This membrane is impermeable to hydrogen ions, so the transfer of the latter through the membrane

Pentose phosphate breakdown of glucose
The pentose phosphate cycle‚ or the hexose monophosphate shunt‚ is often called apotomic oxidation‚ in contrast to the glycolytic cycle‚ called dichotomous (the breakdown of a hexose into two trioses). special

Fats and proteins as a respiratory substrate
Spare fats are spent on the respiration of seedlings that develop from seeds rich in fats. The use of fats begins with their hydrolytic cleavage by lipase into glycerol and fatty acids, which

Elements necessary for the plant organism
Plants are able to absorb almost all elements from the environment. periodic system DI. Mendeleev. Moreover, many elements dispersed in the earth's crust accumulate in plants to a significant extent.

Signs of plant starvation
In many cases, with a lack of mineral nutrients, characteristic symptoms appear in plants. In some cases, these signs of starvation can help establish the functions of this element, and

Ion antagonism
For the normal life of both plant and animal organisms in their environment, there must be a certain ratio of various cations. Pure solutions of salts of any one

Absorption of minerals
The root system of plants absorbs both water and nutrients from the soil. Both of these processes are interrelated, but are carried out on the basis of different mechanisms. Numerous studies have shown

Ionic transport in a plant
Depending on the level of organization of the process, three types of transport of substances in a plant are distinguished: intracellular, near (inside the organ) and distant (between organs). Intracellular

Radial movement of ions in the root
Through metabolic processes and diffusion, ions enter the cell walls of the rhizodermis, and then through the cortical parenchyma are directed to the conductive bundles. Up to the inner layer of the endoderm cortex, it is possible

Upward transport of ions in a plant
The ascending current of ions is carried out mainly through the vessels of the xylem, which are devoid of living content and are an integral part of the plant apoplast. Mechanism of xylem transport - mass t

Ion uptake by leaf cells
The conducting system accounts for about 1/4 of the leaf tissue volume. The total length of the branching of the conductive bundles in 1 cm of the leaf blade reaches 1 m. Such saturation of the leaf tissues is conductive

The outflow of ions from the leaves
Almost all elements, with the exception of calcium and boron, can flow from leaves that have reached maturity and begin to age. Among the cations in phloem exudates, the dominant place belongs to potassium, on

Nitrogen plant nutrition
The main assimilable forms of nitrogen for higher plants are ammonium and nitrate ions. The most complete question of the use of nitrate and ammonia nitrogen by plants was developed by Academician D.N.P

Assimilation of nitrate nitrogen
Nitrogen is present in organic compounds only in reduced form. Therefore, the inclusion of nitrates in the metabolism begins with their reduction, which can be carried out both in the roots and in

Assimilation of ammonia
Ammonia formed during the reduction of nitrates or molecular nitrogen, as well as entered into the plant during ammonium nutrition, is further absorbed as a result of reductive amination of ket.

Accumulation of nitrates in plants
The rate of absorption of nitrate nitrogen can often exceed the rate of its metabolism. This is due to the fact that the centuries-old evolution of plants proceeded under conditions of nitrogen deficiency and systems were developed that

Cellular bases of growth and development
The basis for the growth of tissues, organs and the whole plant is the formation and growth of meristematic tissue cells. There are apical, lateral and intercalary (intercalary) meristems. Apical meris

The law of the long period of growth
The growth rate (linear, mass) in the ontogeny of a cell, tissue, any organ, and the plant as a whole is not constant and can be expressed as a sigmoid curve (Fig. 26). For the first time, this pattern of growth was

Hormonal regulation of plant growth and development
The multicomponent hormonal system is involved in the control of growth and shaping processes of plants, in the implementation of the genetic program of growth and development. In ontogeny in some parts

Effect of phytohormones on plant growth and morphogenesis
Germination of seeds. In the swelling seed, the embryo is the center of formation or release of gibberellins, cytokinins, and auxins from the bound (conjugated) state. From s

The use of phytohormones and physiologically active substances
Role learning individual groups phytohormones in the regulation of plant growth and development has determined the possibility of using these compounds, their synthetic analogues and other physiologically active substances.

Physiology of seed dormancy
Seed dormancy refers to the final phase of the embryonic period of ontogeny. The main biological process observed during the organic dormancy of seeds is their physiological ripening‚ following

Processes that occur during seed germination
During seed germination, the following phases are distinguished. Water absorption - dry seeds at rest absorb water from the air or some substrate before the critical

dormancy of plants
Plant growth is not a continuous process. In most plants, from time to time there are periods of a sharp slowdown or even an almost complete suspension of growth processes - dormant periods.

Physiology of plant aging
The stage of aging (old age and dying off) is the period from the complete cessation of fruiting to the natural death of the plant. Aging is a period of natural weakening of vital processes, from

Influence of microorganisms on plant growth
Many soil microorganisms have the ability to stimulate plant growth. Beneficial bacteria can exert their influence directly by supplying plants with fixed nitrogen, chelating

plant movements
Plants, unlike animals, are attached to their habitat and cannot move. However, they also have movement. Plant movement is a change in the position of plant organs in space.

Phototropisms
Among the factors that cause the manifestation of tropisms, light was the first to be noticed by man. In ancient literary sources, changes in the position of plant organs were described.

Geotropisms
Along with light, plants are influenced by gravity, which determines the position of plants in space. The inherent ability of all plants to perceive the earth's gravity and respond to it

Cold tolerance of plants
plant resistance to low temperatures subdivided into cold resistance and frost resistance. Cold resistance is understood as the ability of plants to endure positive temperatures somewhat in

Frost resistance of plants
Frost resistance - the ability of plants to tolerate temperatures below 0 ° C, low negative temperatures. Frost-resistant plants are able to prevent or reduce the effect of low

Winter hardiness of plants
The direct effect of frost on cells is not the only danger that threatens perennial herbaceous and woody crops, winter plants during the winter. In addition to the direct action of frost

The effect on plants of excess moisture in the soil
Permanent or temporary waterlogging is typical for many regions of the globe. It is also often observed during irrigation, especially carried out by flooding. Excess water in the soil can

Drought tolerance of plants
Droughts have become a common occurrence for many regions of Russia and the CIS countries. A drought is a long rainless period accompanied by a decrease in the relative humidity of the air, soil moisture and

The effect on plants of lack of moisture
The lack of water in plant tissues occurs as a result of its excess consumption for transpiration before entering from the soil. This is often observed in hot sunny weather towards the middle of the day. Wherein

Physiological features of drought resistance
The ability of plants to tolerate insufficient moisture supply is a complex property. It is determined by the ability of plants to delay a dangerous decrease in the water content of the protoplasm (avoidance of

Heat resistance of plants
Heat resistance (heat tolerance) - the ability of plants to endure the action of high temperatures, overheating. This is a genetically determined trait. According to heat resistance, two groups are distinguished

Salt tolerance of plants
Over the past 50 years, the level of the World Ocean has risen by 10 cm. This trend, according to scientists' predictions, will continue further. The consequence of this is an increasing scarcity of fresh water, and up to

Basic terms and concepts
A vector is a self-replicating DNA molecule (for example, a bacterial plasmid) used in genetic engineering for gene transfer. vir genes

From Agrobacterium tumefaciens
The soil bacterium Agrobacterium tumefaciens is a phytopathogen that transforms plant cells during its life cycle. This transformation leads to the formation of a crown gall - o

Vector systems based on Ti-plasmids
The easiest way to use the natural ability of Ti-plasmids to genetically transform plants involves embedding the nucleotide sequence of interest to the researcher into T-DNA

Physical Methods for Gene Transfer to Plant Cells
Agrobacterium tumefaciens gene transfer systems only work effectively for some plant species. In particular, monocots, including major cereals (rice,

Microparticle bombardment
Microparticle bombardment, or biolisting, is the most promising method for introducing DNA into plant cells. Gold or tungsten spherical particles with a diameter of 0.4-1.2 microns cover DNA, o

Viruses and herbicides
Insect-Resistant Plants If cereals could be genetically engineered to produce functional insecticides, we would have

Impact and aging
Unlike most animals, plants cannot physically protect themselves from the adverse effects of the environment: high light, ultraviolet radiation, high temperatures.

Flower color change
Florists are always trying to create plants whose flowers have a more attractive appearance and are better preserved after they are cut. Using traditional crossbreeding methods

Change in the nutritional value of plants
Over the years, agronomists and breeders have made great strides in improving the quality and increasing yields of a wide variety of crops. However, traditional methods for developing new

Plants as bioreactors
Plants provide a large amount of biomass, and growing them is not difficult, so it was reasonable to try to create transgenic plants capable of synthesizing commercially valuable proteins and chemicals.

What is the importance of leaf fall in plant life? Big. The leaves have done their job of providing the tree with nutrients throughout the spring and summer and can now go.

What is the importance of leaf fall in plant life? Important. If the leaves remain on trees or bushes, they will cause their death.

What is the importance of leaf fall in plant life? Philosophical. Leaves die and make room for new shoots.

What is the importance of leaf fall in plant life? Aesthetic. Falling leaves are the most beautiful phenomenon in the world of trees.

Autumn

The leaves of most shrubs and trees change color and fall off. They seem to compete in beauty. But in plants such as alder, young poplar, lilac, the leaves do not change color until frost and remain green. And blacken in the first snow.

Some herbaceous representatives - pansies, shepherd's purse, annual bluegrass - bloom until late autumn.

Periodic phenomena such as flowering or leaf fall in plants are caused by seasonal changes.

Winter

With the onset of autumn, all living things are preparing for winter. Plant life is also dying out. They're in winter period are at rest - do not grow, do not feed, do not live to the fullest, but exist. And with the onset of spring and the beginning of sap flow, the plants receive new strength and are reborn. Surviving a long dormant period is made possible thanks to the supply of nutrients, which are "taken care of" including the leaves. With the onset of cold weather, they become unnecessary for plants. Moreover, they can cause their death.

The leaves evaporate moisture in the summer and could do it in the winter (like clothes are dried in the cold). Thus, they would dehydrate the tree and it would be doomed. Leaf fall in plant life is vital. Protecting themselves from drying out and death, trees and shrubs shed dead parts even before the onset of cold weather.

Autumn leaves

Before falling off, they give the plant. A cork forms at the base of the petiole of the leaf, and it dies. Then it separates from the branch under its own weight or from a gust of wind. The importance of leaf fall in plant life cannot be overestimated. Without it, a huge part of the flora would die, only coniferous and tropical specimens would remain.

evergreens

They are characterized by a constant color of the leaves. This does not mean that they live forever. In evergreen crops, leaf fall allows plants to constantly renew themselves. They shed dead parts throughout the growing season, just like human hair. In evergreens, old leaves fall off. Younger ones remain unchanged in color.

Tropical evergreens are characterized by leaves that have a growing season of several years or months. Although there are also specimens that remain with bare trunks for a short time.

How long do leaves live

Their life expectancy varies and can range from 14 days to 20 years. Leaves in comparison with the root and stems live much less. This is due to the fact that they function very actively and do not have the opportunity to be updated.

In evergreens of central Russia, such as spruce and pine, the needles fall off after 5-7 years for the first and after 2-4 years for the second.

The duration of leaf fall is also not the same. In birch, this period lasts about two months, and in linden, only two weeks are enough.

Why do leaves change color

The fact that the tree is preparing for winter becomes evident from the change in the color of the leaves. They are magnificent in their withering - yellow, red, brown, orange with various transitions and shades. It becomes sad when all this beauty flies around and covers the earth with a continuous carpet.

Leaf fall is a biological process that is inherent in the life and development of a plant. The intensity of all intracellular processes (photosynthesis, respiration) decreases, the content of nutrients (ribonucleic acid, nitrogen and potassium compounds) decreases. Hydrolysis begins to predominate over the synthesis of substances, cells accumulate decay products. More valuable plastic and mineral compounds from the leaves go into the storerooms of the plant.

Most shrubs and trees turn purple and yellow in autumn. Red shades are due to the accumulation of anthocyanin pigment in the cells, which reacts to acid and changes color to a purple hue. In an alkaline environment, it would turn bluish-blue.

The yellow color of leaves depends on pigments (carotene, xanthophyll) and cell sap (flavones). This is how, very prosaically, the beauty of the autumn forest is explained.

Fertilizer

The role of leaf fall in plant life is very significant. It protects the roots from freezing. The lush forest floor, due to its friability and the presence of a large amount of air, reduces the thermal conductivity of the soil and prevents its deep freezing in winter.

In addition, it is quite moisture-intensive, which is important for plants. Fallen leaves serve as mulching material, protect the soil from erosion and prevent the formation of a crust. Rotten, they improve the structure of the soil and attract earthworms.

Fallen leaves are valuable organic fertilizer with the content of phosphorus, potassium, calcium, nitrogenous substances and useful microelements. Thus, favorable conditions for plants are created. Huge trees grow in the forests without any fertilizer.

Fallen leaves in the garden

The modern gardener does not appreciate the peasant experience of the past. It annually burns as much fertilizer and structural material as would be enough for both compost and mulching. Some gardeners do not save leaves out of ignorance, others are afraid of the spread of infections. But if you approach this issue reasonably, then all their fears are in vain.

The fact is that pathogens die when the compost ripens and is processed by earthworms. Therefore, the leaves fruit crops it is advisable to lay in order to obtain humus, and leave a healthy pillow from under birch, linden, chestnut, maple, etc. for mulching for the next summer period.

Shelter of this kind will be a salvation for valuable plants in snowless winters. For example, for strawberries, daffodils, new plantings.

In the spring, fallen dry leaves can be used to mulch plantings of peppers, eggplants and tomatoes in greenhouses and greenhouses. These crops require dry air and moist soil. A thick layer of dry leaves will create the necessary microclimate, become an obstacle to the growth of weeds, and will delight in a single greenhouse all summer.

early harvest

The valuable properties of leaf fall can be used for growing early crops of vegetables (cucumbers, potatoes, cabbage, zucchini, etc.) or for the accelerated planting of strawberry bushes and flowers. Since autumn, they have been preparing shallow, bayonet spades, trenches. Then they are filled with healthy fallen leaves and spilled with a solution of slurry. Juicy cabbage leaves, tops of root crops, etc. are placed on top. In this form, trenches are left for the winter. The excavated earth is left nearby in the form of a ridge.

During the winter, the contents of the trench will settle, be saturated with melt water and compact. The ground in the ridge under the bright sun will thaw and warm up faster. As soon as the soil allows, the roller is raked into the trench and planted early vegetables. You can build a small film tunnel over young plants to protect them from frost.