And how they change their color in the fall. Molecules responsible for bright shades yellow and orange are no longer a mystery, but why the leaves turn red is still a mystery.
Reacting to change in air temperature and fewer daylight, the leaves stop producing chlorophyll(which gives green color), which absorbs blue and partly red light emitted by the sun.
Since chlorophyll is sensitive to cold, some changes in weather, such as early frosts, will "turn off" its production faster than usual.
Why do leaves turn yellow and fall
During this time, orange and yellow pigments called carotenoids(which can also be found in carrots) and xanthophylls shine through leaves that have no green left.
"The yellow color is present in the leaves all summer long, but it is not visible until the green disappears," says Paul Schaberg(Paul Schaberg), plant physiologist with the US Forest Service.
But scientists still have little information about the red color that appears on some leaves in the fall.
The color red is known to come from anthocyanides, which, unlike carotenoids, are produced only in autumn. Anthocyanides also give color to strawberries, red apples and plums.
Trees release anthocyanins when they sense a change in environment - frost, ultraviolet radiation, drought and / or fungus.
But the red leaves are also a sign of illness wood. If you notice that the leaves of the tree turned red earlier than usual (at the end of August), most likely the tree is suffering from a fungus, or it was damaged somewhere by a person.
Why does a tree waste its energy to produce new anthocyanidins in a leaf when that leaf is about to fall off?
Paul Schaberg believes that if anthocyanides help the leaves stay on the tree longer, they can help the tree absorb more nutrients before the leaves fall off. The tree can use the soaked resources to bloom in the next season.
Anthocyanins
The topic of anthocyanins is a little more difficult to study than the rest of the components of trees. While all trees contain chlorophyll, carotene, and xanthophylls, not all produce anthocyanins. Even trees that have anthocyanins only produce them under certain conditions.
Before the tree gets rid of its leaves, it tries to absorb as much as possible. more nutrients of them [leaves], at which point anthocyanin comes into play.
Scientists have several answers to the question of why some trees produce this substance, and the leaves change their color.
The most common theory suggests that anthocyanins protect the leaves from excess sunlight, while allowing the tree to absorb the nutrients stored in the leaves.
On wood, these pigments play the role of sunscreen blocking dangerous radiation and protecting the leaves from an overabundance of light. They also protect cells from freezing quickly. Their benefits can be compared to those of antioxidants.
Plenty of sunshine, dry weather, frosty weather, low level nutrients and other stressors increase the concentration of sugar in tree sap... This triggers the production mechanism. a large number anthocyanins, in a last-ditch effort to store energy to survive the winter.
Scientists believe that the study of anthocyanins help to understand the level of the disease every tree. This, in turn, will provide a clearer picture of environmental problems in the future.
As the character of the book and cartoon said Lorax: "The color of the trees will one day be able to tell us how it feels on this moment wood".
Why do leaves dry and fall
With the coming of winter, part the globe gets less sunshine and the air gets colder. When these changes occur, the trees prepare for winter.
The trees that cast their leaves clog the attachment points of the leaves... This prevents liquids from useful substances reach the leaves, which is why the leaves change their color and fall off.
Leaf fall symbolizes not only the change of season, this process also helps the tree survive the cold, dry winter air.
In winter, trees do not receive enough liquid to "contain" leaves... If they didn’t clog the places where the leaves begin to grow, the trees would simply die.
When spring brings warm air and water, trees begin to grow new leaves.
Why don't conifers shed their leaves?
Why in the fall the leaves turn yellow and fall
Summer season ends with the last fallen leaves from trees and shrubs. For many people, bare plants cause despondency and yearning for summer. But autumn is beautiful! No wonder there are so many poetic lines dedicated to this time of the year. Why do the leaves of some plants turn red, while others turn yellow? And why do the leaves fall?
Leaf fall is the brightest sign of autumn. These plants adapt to the unfavorable conditions of the season. Seasonal plant variability begins in northern latitudes and gradually moves south. Leaf fall is repeated every year and always delights us with its bright colors- from yellow and orange to pink and purple. Leaves fly around even with evergreens in the subtropics and tropics. Only there they do not fall all at once, but gradually throughout the year, and from that it is not so noticeable.
It gets colder in autumn, and water flows into the plants from the roots to the leaves in slow motion. But it is not main reason leaf fall. The onset of unfavorable conditions is a signal for the transition of plants to a new cycle of life, which is laid down in genetic code... This indicates to us that the fall-off of leaves is not a direct consequence of unfavorable conditions. It together with winter period dormancy is included in the very cycle of plant development. There is also a way to make sure that leaf fall is a physiological process. Why is the leaf separating from the branch? It turns out that with the onset of cold weather at the base of the petiole, where the leaf is attached by a “leaf pad” to the branch, a cork layer is formed. The cells of this layer have smooth walls and are easily separated from each other. As soon as the wind blows a little harder, and the leaf is separated from the cork layer.
The green color of the leaves in summer is due to the large amount of chlorophyll pigment they contain. This pigment "feeds" the plants, because it is with its help that in the light the plant synthesizes organic substances from carbon dioxide and water, and first of all the main sugar - glucose, and from it - all the rest nutrients... Chlorophyll contains iron, and when it breaks down, oxides are formed, which have a brown-yellow color. The destruction of chlorophyll occurs more intensely in the light, that is, in sunny weather. That's why the cloudy rainy autumn leaves retain their green color longer. When sunny days come in autumn, the leaves take on a golden-red color.
However, along with chlorophyll green leaves contain other pigments - yellow xanthophyll and orange carotene (it determines the color of carrots). In summer, these pigments are invisible, as they are masked by a large amount of chlorophyll. In autumn, as the vital activity in the leaf fades, chlorophyll is gradually destroyed. This is where the yellow and red shades of xanthophyll and carotene appear in the leaf.
In addition to gold, the autumnal outfits of trees contain crimson hues. This color is responsible for a pigment called anthocyanin. Unlike chlorophyll, anthocyanin is not bound inside the cell with plastic formations (grains), but is dissolved in the cell sap. With a decrease in temperature, as well as in bright light, the amount of anthocyanin in the cell sap increases. In addition, stopping or delaying the synthesis of nutrients in foliage also stimulates the synthesis of anthocyanins.
Fallen leaves can retain their shape and color for a few more days, and then they begin to dry out and acquire a brown color, not very pleasant to the eye. Part of the leaves remains in place under trees and shrubs, and part of the wind blows off the site. For aesthetic reasons, the gardener is often tempted to clear the soil of fallen leaves. Is it necessary? After all, the leaves contain the same chemical compounds that were taken from the soil by plants. True, they acquired a slightly different chemical composition and entered the formed plant organic matter... Once on the surface of the soil, the leaves become "prey" for a great variety of different living organisms. Among them, the most important role in leaf utilization belongs to earthworms. Their waste products (excrement of worms are called caprolites) contain the entire set of nutrients for plants in almost finished form... So the leaves, having got into the biological cycle of substances, returned to the soil, what they once received in the plant.
Now decide for yourself - to remove the foliage from under the trees or not? There are two ways to save useful properties fallen leaves. The first is to leave it in place until spring, followed by digging. At the same time, the leaves will insulate upper layer soil. The second path will be somewhat more difficult and take longer. Collect the leaves in compost pit and after a year or two, return it under the trees in a rotted form.
V. A. Rassypnov , professor of ASAU
Sasha K. (Belogorsk)
In what period does the leaf fall of linden and birch begin and end?
With the onset of September, the trees gradually begin to change the summer emerald green color of the leaves to autumn yellow. A little more time will pass and all the golden foliage will rush to the ground. Observing nature, people often ask the question - when does the leaf fall of birch, linden, maples and other favorite yellowing trees end? Let's try to answer this question.
When the leaves turn yellow
The foliage begins to change color long before the first frost. As a rule, this happens at the end of August, when the day has already noticeably shortened and got a little colder, and lasts for 14-20 days. At first, only a few gray-yellow areas are visible on the branches, but day after day there are more and more of them.
By mid-September, the birch leaves become ocher-gold and gradually begin to fall off. Maple branches are no less beautiful at this time. The crown of the tree is covered with foliage of yellow, brick-red, red and even purple shades... Linden foliage stands out, which is only half yellowed.
The beginning of leaf fall
In many trees, leaf fall is uneven, that is, it happens in different time... For example, after the first strong frost, linden and maples start falling leaves. By this time, the birch had already dropped most of the leaves. Her leaf fall begins in the first decade of September and lasts 15-20 days.
Important! The beginning of leaf fall depends on the weather. Dry sunny weather and calm days delay golden decoration trees.
Leaf fall is especially abundant after the third frost. Leaves fall very densely to the ground, forming a thick litter on the ground. Birch drops about 30 kg of leaves in autumn. In an adult linden and maple, this amount reaches 40-50 kg.
End of leaf fall
The end of leaf fall, as a rule, is accompanied by a significant cooling, worsening weather conditions, frequent rains and strong gusts of wind. By October 7-10, lindens and birches lose their last yellow leaves. Maples become bare much later, only by October 20. Single leaves can be kept on the branches until mid-November, reminding passers-by about the past golden time of the year.
Observation of nature during the fall of leaves
The period of active leaf fall is accompanied by a significant cooling and the arrival of night frosts. Summer white clouds are replaced by a solid gray shroud. There is often fog in the morning. The first flocks of migratory birds rush into the sky.
The end of leaf fall in linden and maples is accompanied by gloomy rainy weather, frost on the still green grass and thin ice on puddles. Rooks flock and fly south. The earth gradually cools down and nature falls asleep.
Autumn leaf fall: video
Spathiphyllum is an easy-care plant that can often be seen in offices and apartments. It does not take much work for the flower to produce lanceolate foliage and to produce peduncles with white bracts. But sometimes it starts to lose its color. There are several reasons why spathiphyllum leaves turn yellow.
Lack of micronutrients
The leaves of a flower can turn pale yellow very quickly. And they can be a sign different problems... Due to the fact that the symptoms are so similar, even experienced florists the first time it is difficult to determine the reason for the behavior of your plant. If the foliage begins to wither, then this will necessarily entail the weakening of the entire plant. When the leaves of the spathiphyllum turn yellow, this may also signal that putrefactive processes have begun on the roots.
Poor conditions of detention are the main reason why spathiphyllum turns yellow. What to do in this case must be decided based on the type of problem. If the bush bloomed abundantly and bloomed for a long time, then yellow foliage is a sign of fatigue, the plant wasted its strength and nutrients. In this case, the lower foliage begins first turn yellow evenly and then fade.
It is necessary to apply fertilizers if the leaves of the spathiphyllum have drooped, which should be done at least twice a year. If there are not enough individual nutrients in the soil or the plant itself is poorly nourished, the foliage may turn yellow entirely. For top dressing, purchase a universal compound fertilizer.
Spathiphyllum reacts sharply to a lack of magnesium. If this element is not enough for him, then the bush itself will be sluggish, its growth will slow down significantly. In this case, the veins on the leaf will remain green, but the tissues between them will turn brown or yellow. In this case, magnesium sulfate should be included in the fertilizer.
It may also be necessary to transplant a flower if you have not done this for a long time: pick up a looser pot, choose a loose nutritious soil in which the plant takes root best. A transplant is best done every spring.
Correct lighting
If the tips of the foliage are still pale and yellowish, it is possible that the plant is often exposed to direct sunlight. the brightness of the greenery began to disappear intensively, then the answer may be hidden in the fact that you often expose the pot to sunlight. Spathiphyllum loves light but the hot summer sun is common reason the appearance of yellowness. The plates can be severely burned. And if the sun is not enough, then the foliage turns pale, its growth slows down.
Dry air
In winter, the main enemy of spathiphyllum is dry air. ... If the bush is located nearby with heating appliances, then you are unlikely to be able to avoid wilting of foliage. Yellowing begins at the tip, and then spreads throughout the leaf plate. The plant weakens, flowering stops. A number of measures need to be taken:
- remove the bush away from heating;
- place a container with clean water next to it;
- use a spray bottle to spray the foliage;
- use humidifiers.
Then the plant will answer your care with the splendor of greenery, good and frequent flowering. If the foliage did not have time to be badly damaged, then over time it will acquire the same color, but it is better to remove the dried leaf plates in a timely manner so that they do not turn into a breeding ground for pests and harmful fungi.
Watering errors
If you have violated the watering regime, then foliage discoloration will start from the edges - a dried black border will begin to form there. Therefore, it is worth returning to the previous watering and following the general recommendations:
It is recommended to reduce the frequency and intensity of watering in winter. In summer, however, the demand for water increases. But all the same, you should never oversaturate the soil with moisture! To reduce evaporation, mulch the soil with sphagnum moss or pebbles.
Diseases and pests
Yellow foliage may indicate disease or pest damage. Most often, such a bush is attacked. spider mites, thrips and mealybugs... First you need to identify the source of the danger, and only then resort to the treatment of your green handsome... Treatment is as follows:
- the bush needs to be treated with insecticides;
- if soil pests have appeared, then it must be transplanted into another container and fed with nutrients;
- for prevention, use disinfected soil: it will help protect the flower from possible infection with harmful fungi.
If the lower foliage turns yellow, begins to dry out, brown spots grow, after which they move to neighboring leaves - this is a sign of a fungal disease... Urgent measures must be taken before the disease spreads to the roots and stems, otherwise the plant will suffer irreparable damage.
Need to handle it special drugs(fungicide), then transplant into a new container, after removing the affected areas so that the disease does not spread. In addition to the leaves, you need to inspect the stem and roots: the fungus often infects them.
Spathiphyllum is called yet " female happiness» - it is believed that he helps women meet their soul mate or establish harmonious relationship in family. But even if you don’t believe in the omens, you cannot help but notice how this spectacular plant with bright leaves and unusual flowers decorates the interior, how much more comfortable it becomes in the house with it.
And although spathiphyllum is not capricious, but keep your decorative view he can only with appropriate care. The plant needs to be regularly inspected and urgently taken action if the leaves of the spathiphyllum turn yellow. What to do in this case, you can decide based on the accompanying factors: solve the issue with lighting or watering, feed the plant or transplant it. In response to your concern, Spathiphyllum is sure to delight you with lush foliage and beautiful flowers.
Attention, only TODAY!
Every autumn, the leaves change their color, they turn yellow, turn red or turn purple and gradually fall off, become dry and brittle. The rustling occurs precisely because of these properties. in the fall? Some believe that this is due to frost. As if this cold killed the summer beauty, and now the leaves fall to the ground, gradually covering it with a bright rustling carpet. However, this is not at all the case. If you are careful, you will immediately notice that the leaves begin to turn yellow and fall off much earlier than the first frost. Leaf fall is only a seasonal phenomenon, and its causes are hidden in the trees themselves, in their biological mechanism of struggle for survival in harsh seasonal conditions.
A small child asks his parents why the leaves turn yellow in the fall? It is very important to answer this question correctly. Indeed, based on what children are told in their small years, their further worldview is formed. If the leaves do not fall off in time, then the plants may suffer or die not from freezing, but from lack of moisture. Cold air can dry no less hot. The liquid in the soil freezes, and the suction capacity of the roots is suspended, and soon completely freezes. When the flow of moisture to the leaves stops, it still continues through their surface. This is why the leaves turn yellow in the fall. They protect their tree from death. If they remained on the tree, then all the moisture would immediately evaporate from the branches through their surface. Thanks to this protective mechanism, plants are freed from a large excess area. And in order for a tree to throw them off, you first need to turn the leaves into dead ones, which then fall off.
When the leaves turn yellow in autumn, all processes in the plant stop, life itself stops. This is one of the irreversible phenomena of nature. When the illumination on the street changes, the biological clock of the leaves is triggered, and they begin to change color. This process can be divided into three stages:
- yellowing of some leaves;
- coloring the illuminated sides of the crowns,
- completion of the process and the first drop.
It is impossible that all trees do this at different times, and the forest becomes bright unevenly. When do the leaves start to turn yellow? In the autumn. On the lighted side of the tree, the process is faster, and on the shaded side of the tree, the leaves retain their green color for a long time.
From point of view biochemical process this is due to the fact that they stop producing chlorophyll. V summer time yellow pigment is also present in the leaves, however, compared to green, its amount is insignificant. Now it becomes more and more visible. And another one interesting feature: Red foliage is found only in a well-lit and cool enough place. Anthocyanins, together with carotenoids, are responsible for the rich color.
All of this explains why the leaves turn yellow in the fall. However, this does not happen with all trees. The leaves of wild rosemary, cranberry, juniper, heather and lingonberry do not turn yellow, they remain green under the snow, since they evaporate very little moisture.
