Why do the leaves of some plants turn red in autumn

Why do the green leaves turn yellow and fall off in autumn? Originally, it was thought that it was the result of the dry autumn and the loss of moisture in the leaves. But in previous years, scientists have discovered that the discoloration of leaves is linked to changes in certain hormones and chemicals.

In early autumn, the hormone abscisic acid and other substances accumulate in the leaves, and the leaves begin to change color, and the leaves return useful materials such as chlorophyll, water, nitrogen, phosphorus, protein and carbohydrates to the trunk and roots, waiting for them to wither and die. At the same time, a group of special cells in the leaf peduncle also begin to become fragile, so that in case of wind and rain, they can easily break off, and the leaves fall all over the ground.

Botanists point out that the color of the leaves in autumn is sometimes dark and sometimes light, depending on the amount of rainfall or snowfall. In dry years, the color of the leaves does not change too much, and the leaves fall earlier, which is to retain more moisture for the trees. Storing nutrients, keeping more water, and falling leaves are a means for trees to "lose their pawns and protect their cars".

In this way, it is really unnecessary for some literati and inkmen to complain when they see the fallen leaves.

Some green leaves turn red when the weather is cool. Beijingers will go to Xiangshan to see the red leaves in autumn, and Nanjing people also like to go to Qixia Mountain to enjoy the beautiful scenery of "ten thousand mountains are red". Maple trees, maple trees, black trees, cochinese, persimmon trees, etc., will become fiery red before and after the frost falls.

Frost leaves red in February flowers". They are embellished with golden autumn, attracting countless tourists and decorating the country more delicately.

Whether it is yellow or red leaves, under the cold winter wind, the leaves of deciduous trees eventually fall off, leaving only bare trunks. Then, in the tropical areas where the seasons are always summer, don't the leaves need to fall? No.

Tropical trees also lose their leaves. However, they always lose their leaves during the dry season. Take Guangdong, Yunnan, Hainan and other places in China as an example, many trees only lose their leaves in February and March every year.

The saying "a leaf knows autumn" does not apply in these places; "When a leaf falls, you know the autumn of the world", it is even more inconsistent with the reality of nature.

Chlorophyll is lost, leaving lutein and carotene.

I also want an answer to this question.

The reason for the discoloration of the leaves is related to the chemicals inside it – chlorophyll, carotenoids, anthocyanins, etc. It is also the result of the comprehensive effect of external temperature, temperature difference, light and other factors. In spring and summer, chlorophyll synthesis is greater than decomposition, and the leaves are green; Autumn is coming, the temperature drops, and the amount of chlorophyll synthesized is less than the amount of chlorophyll that is decomposed.

When its content decreases, other chemical pigments appear. If the ratio of carotenoids (lutein and carotene) is high, the leaves will appear yellow or orange; In late autumn, due to the low temperature, the ability of the leaves to transport sugar and water is weakened, and the concentration of glucose increases, and the increase in soluble sugars makes the cells acidic.

Under acidic conditions, anthocyanins turn red, as do leaves with a high proportion of anthocyanins. Of course, leaf discoloration is a complex process. When the cold air is strong, the temperature drops, causing low temperatures.

After that, the weather was sunny and the temperature difference was large. Such meteorological conditions promote the rapid conversion of chlorophyll into carotenoids and anthocyanins in the leaves. The external change is that the color of the leaves gradually changes from green to yellow, orange, red.

You should be familiar with chlorophyll, because almost all natural plant leaves contain chlorophyll. Through chlorophyll, the leaves absorb the energy needed by the sun and extract nutrients from water and carbon dioxide. Chlorophyll occupies a very important place in plants.

Chlorophyll is green and is the main chemical hidden in the leaves. In spring and summer, the color of the leaves is green.

With the arrival of autumn, the days become shorter and the plants photosynthesize less, so the leaves contain very little chlorophyll and will slowly change to other colors. Colors of many plants, fruits, vegetables, etc. All are related to anthocyanins, which are water-soluble natural pigments.

The color of anthocyanins is affected by a variety of factors, such as low temperature, lack of oxygen, etc., which will reduce the formation of anthocyanins. Anthocyanins can absorb green light, blue light, etc. In autumn, anthocyanins increase rapidly, showing more vibrant colors such as scarlet, purple, etc.

Because the proportions of the leaves are different, the color will also be different. In fact, there are many reasons for leaf discoloration, but the above three reasons are the main ones.

Leaf discoloration is also related to temperature, humidity, soil, pH, but light is important. Autumn is much less sunny than summer, so the leaves turn from green to yellow. As winter approaches, many changes take place in the plants.

Temperatures drop and daylight hours are shortened. The green tones of the leaves have disappeared, and other colors covered in chlorophyll can now be seen, replaced by the stunning splendor of autumn. Temperature can also affect the color of autumn leaves.

The higher the temperature, the brighter the color, and vice versa. Some trees shed their leaves, while others do not. In the north, winters are colder, forcing most tree species to lose their leaves, with a few exceptions.

In autumn, there are many tree species whose leaves turn red, such as persimmon trees, Nantian bamboo, black tree and so on.

The reason for this is mainly related to the natural pigments contained in the leaves. Generally, the pigments contained in leaves are lutein, chlorophyll, carotene, anthocyanins, etc. Chlorophyll is a substance that uses carbon dioxide and water to synthesize nutrients in the presence of sunlight.

The red color of the leaves is mainly anthocyanins, and the leaves turn red when they encounter acidic conditions. In autumn, due to light and temperature, the water in the leaves gradually loses, and the acidity in the leaves gradually becomes thicker, and the leaves turn red. This is the reason why some leaves turn red.

The reason why some leaves turn red in autumn is that the leaves contain a lot of pigments, such as chlorophyll, lutein, carotene, etc.

Chlorophyll is darker in color and often covers other pigments in summer, giving it a dark green color.

But when autumn comes, when the sun is still strong and the temperature slowly drops, the chlorophyll will gradually disappear due to destruction.

At this time, the yellow lutein and carotene are displayed, and this is the reason why the leaves turn yellow in autumn.

There are also plants that produce a large amount of red anthocyanins before the leaves fall under strong light, low temperature, and drought conditions, which is the reason for the formation of red leaves.

In autumn, many trees lose their leaves, and the leaves tend to turn yellow before the leaves fall, but there are a few species whose leaves turn scarlet, called "red leaves".

We know that leaves contain a lot of pigments, such as chlorophyll, lutein, carotene, etc. Chlorophyll is darker in color, often covering other pigments in summer and showing a strong green color, but when autumn comes, the sun is still strong, the temperature is slowly decreasing, chlorophyll will gradually disappear because of destruction, then yellow lutein, carotene will be displayed, autumn leaves turn yellow is this reason. There are also plants under strong light, low temperature, and drought conditions, and the leaves will produce a large amount of red anthocyanins before they fall, which is the reason for the formation of red leaves.

According to statistics, there are about a few thousand species of trees whose leaves can turn red. The leaves of most plants generally only have a lifespan of a few months from birth to death.

The reason why the leaves of some plants turn red in autumn is because the leaves of plants contain many natural pigments, such as chlorophyll, lutein, anthocyanins and carotene. When exposed to sunlight, chlorophyll can use water and carbon dioxide to produce nutrients for plant growth.

In spring and summer, the sun and water are abundant, the plants grow vigorously, the chlorophyll is very active, and the color is darker, so it is always green and verdant. However, in autumn, due to the decrease in temperature, some leaves begin to wither, and some leaves are destroyed and the chlorophyll gradually disappears. At this time, yellow lutein, yellow or orange carotenoids take the opportunity"Show up", the green leaves turned into yellow leaves.

In autumn, under the conditions of strong light, low temperature and drought, the red anthocyanins surge, which are present in the surface cells of the leaves, and when there is more sunlight than lutein, the leaves turn a bright red.

Red leaves are not caused by the pigments of the chloroplasts in the leaves, but by the anthocyanins in the cell vacuoles. As the temperature drops in autumn, plants accumulate more sugar to adapt to the cold, and there are more soluble sugars in the body, so more anthocyanins are formed and stored in vacuoles. Anthocyanins, on the other hand, are similar to acid-base indicators, and will show a color gradient from blue to red from alkaline to acidic, specifically, lilac at pH=7 8; at pH <3, it is red; pH>11 is blue.

The leaves turn red due to the increase in anthocyanins in the vacuoles in autumn and the acidic pH of the cell fluid.

This is because as the environment changes, the leaves of plants begin to senesce, and chlorophyll is broken down in large quantities (the leaves appear green because the leaves contain chlorophyll), while pigments such as lutein and carotene are still retained. Thus, giving the leaves a red or yellow appearance.

The leaves of maple, oak, black tree, birch and other trees turn red in autumn.

The chlorophyll in the leaves usually breaks down in the fall, and the nutrients in the leaves are redistributed to the trunk and roots to help the trees survive the sun-scarcity winters. When the leaves lose their chlorophyll, the yellow carotenoids that are already present in them are revealed, which is the reason why the leaves of some trees turn yellow in autumn. The reddening of leaves is mainly caused by anthocyanins, which are usually produced by the leaves in autumn.

The latest research shows that the poorer the soil, the more trees need nutrients from their leaves, and the more likely the leaves are to turn red in the fall. Chinese scientist William Oak points out that trees growing on poor soils have higher nutrient requirements, and their leaves are more likely to turn red because anthocyanins may act like sunscreens to prevent leaves from falling prematurely due to sun damage in the fall, allowing trees to draw more nutrients from their leaves.

The leaves of maple, oak, black tree, birch and other trees turn red in autumn. Among them, the triangular maple is the most beautiful, this kind of maple leaf is triangular, and the frosted leaves are not turned red all at once, but first from green to yellow, orange, and then purple, so it is also called "five-color maple".

Many such as maple and maple.

To put it simply: there are three main pigments in plant mesophyll cells: chlorophyll, lutein and carotene, and the synthesis of these three pigments is related to temperature. When the temperature drops in autumn, the secretion of carotene increases, and carotene is orange, so the leaves turn yellow or red.

Specific explanation: In the leaves of plants, there are many natural pigments, such as chlorophyll, lutein, anthocyanins, and carotene. The color of the leaves is due to the different content and proportion of these pigments.

In spring and summer, the content of chlorophyll is larger, while the content of lutein and carotene is much lower than that of chlorophyll, so their color cannot be revealed, and the leaves show the green color of chlorophyll. Because the synthesis of chlorophyll requires strong light and higher temperature, in autumn, as the temperature drops, the light becomes weaker, the chlorophyll synthesis is blocked, and the chlorophyll is unstable, and the light is easy to decompose, and the decomposed chlorophyll can not be replenished. Therefore, the proportion of chlorophyll in the leaves decreases, while lutein and carotene are relatively stable and not susceptible to external influences.

As a result, the leaves show the yellow color of these pigments.

In the leaves of plants, there is a starch produced by photosynthesis, which can only be transported to various parts of the plant when it is converted into glucose. However, in late autumn, when the weather becomes colder, the starch produced by the leaves during the day cannot be completely converted into glucose at night due to the weakening of the transport effect, and the moisture in the leaves is gradually reduced, so the glucose remains in the leaves, and the concentration is getting higher and higher. The increase of glucose and the low temperature in autumn are conducive to the formation of anthocyanins.

Therefore, the anthocyanin content gradually increased while the chlorophyll content gradually decreased. Anthocyanins are unstable organic substances that have no color of their own and turn red when it encounters acids and blue when it encounters alkaline substances. In this way, the anthocyanins turn red in the acidic mesophyll cells, so the leaves turn bright red.

Maple leaves, fir leaves, black tree leaves, birch leaves, etc.

Because the leaves contain anthocyanins, this pigment is usually produced by the leaves in autumn.

Anthocyanin is a water-soluble plant pigment, which is present in the cell fluid in the vacuole, and can change color with the acidity and alkali of the cell fluid, and is commonly found in the tissues of flowers and fruits, as well as in the epidermal cells and lower epidermal layers of stems and leaves.

It is a natural antioxidant after it is combined with carbohydrates with glycosidic bonds, which is related to the color of flowers and the reddening of leaves. It can change color with the acidity and base of the cell fluid.

The cell fluid is reddish if it is acidic, and it is bluish if it is alkaline.

Leaf chlorophyll is associated with seasonal temperature and the result of photosynthesis.

In autumn, when the temperature is cold, the chlorophyll contained in the leaves of plants is destroyed and gradually disappears. The yellow lutein turns into yellow leaves, and then under strong light, low temperature, and drought conditions, the red anthocyanins proliferate, which are present in the surface cells of the leaves, and when there is more sunlight than lutein, the leaves turn a brilliant red.