Why are the leaves green? Why does it turn yellow?

As the temperature drops, the hours of daylight become shorter, and the photosynthesis decreases, and the chlorophyllin decreases, causing the leaves to gradually turn yellow.

Because in the spring, it is well developed and there is plenty of chlorophyll, so it is green. Because of the decrease in nutrients in autumn, there is also a shortage of water, and chlorophyll disappears.

The leaves do not absorb green, so this color is reflected and the human eye sees green. In addition to chlorophyll, the leaves contain chlorophyll.

In addition, it also contains carotene.

and lutein, when autumn comes, chlorophyll will decompose in the leaves if it is not resistant to low temperatures, while orange carotene and lutein are more stable and will show orange on the leaves.

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 be 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.

The reasons why the leaves turn yellow are as follows:

1. Lighting problems.

Strong light exposure can easily cause the leaves to dry up and yellow, and the plants cannot be directly exposed to strong light for a long time, so they need to be placed in a cool place and properly shaded.

Lack of light can also cause the leaves to turn yellow, so you need to put the plants in a sunny place to ensure a certain amount of light time.

2. Watering problems.

Excessive watering can easily cause dull and yellow leaves, so you need to control the amount of water and keep the flower soil moist during plant growth. It is necessary to observe the growth state of the plant, water it reasonably, and be careful not to accumulate water to avoid root rot.

Watering too little can also cause the leaves to turn yellow, and if the potting soil is too dry, it needs to be watered promptly.

3. Fertilization problems.

Lack of fertilizer in plants will cause yellowing of leaves, if the soil fertilizer is not enough, it is necessary to apply thin fertilizer frequently to supplement nutrients.

Excessive fertilization of plants will also cause the leaves to burn and fall off, so they should be fertilized reasonably, and if there is too much fertilizer, they should be stopped and watered in time.

4. Soil. If the soil is alkaline, the leaves of the plant tend to show old leaves and the middle of the leaf veins turn from green to yellow. At this time, it is necessary to add some acidic substances to the soil to neutralize.

With the arrival of autumn, the leaves of various trees show different changes one after another, such as:

Ginkgo biloba: The leaves turn green to golden and remain on the tree for a certain period of time before falling off.

Maple trees: The leaf color changes from green to yellow or red, and there is also a certain amount of lingering time for people to enjoy.

Cochinese, persimmon trees, torch trees: Also in autumn, they change from green to red.

Plane tree: The leaf color changes from green to yellow-brown, and it sheds intermittently, and some leaves can be hung on the tree until the Spring Festival.

Willow: Although it is a deciduous plant, its leaves are green even in late autumn.

Boxwood: In late autumn, when the weather cools, the leaf color turns from green to brownish-red, and sometimes the color is green and red because the temperature is not too low.

Aspen: In late autumn, if there is no frost, it is generally green and does not fall off, and if there is frost, the leaves become darker and fall off.

Crape myrtle: The leaf color changes from green to brown and falls off quickly.

Leaves are an important part of the tree's photosynthesis and nutrient production, and the leaves turn yellow because the chlorophyll is destroyed, leaving only lutein. In spring and summer, when the weather is warm, the trees are very nutritious, and they produce a lot of chlorophyll, so the leaves are green. When the weather becomes colder, the trees are undernutrient, the chlorophyll slowly decreases, and the anthocyanins and lutein increase, and the leaves turn red or yellow.

When the weather is colder, the anthocyanins and lutein in the leaves will slowly be broken down, and the leaves will turn a deep brown. The photosynthesis of leaves is done through chloroplasts, which absorb carbon dioxide, release oxygen, and provide shelter and food for the flora and fauna of the forest.

Introduction to photosynthesis

Photosynthesis is usually the process by which green plants (including algae) absorb light energy and synthesize carbon dioxide and water into energetic organic matter while releasing oxygen. It mainly includes two stages: light reaction and dark reaction, which involves important reaction steps such as light absorption, electron transfer, photosynthetic phosphorylation, and carbon assimilation, which is of great significance for realizing the energy conversion in nature and maintaining the carbon-oxygen balance of the atmosphere.

Eukaryotic algae, such as red algae, green algae, brown algae, etc., have chloroplasts like higher plants and are also capable of oxygen-producing photosynthesis. Light is absorbed by chlorophyll, and many algae have other different pigments in their chloroplasts, giving them different colors.