Why do autumn fall, why do autumn leaves fall

Trees shed their leaves in autumn to minimize water transpiration and survive the winter safely. Otherwise, in the season of freezing weather and howling winds, it is already difficult for the roots to absorb water, but the transpiration of the leaves continues as usual, and the trees will only have a dead end.

Adapt to natural climate change, reduce transpiration, prevent the loss of water and nutrients, and maintain temperature.

Maintain body temperature to reduce heat dissipation.

Plants are scarce in autumn.

The reason why the leaves fall off in autumn.

The leaves of plants play an important role in the biosphere. They use solar energy to synthesize nutrients and expel oxygen into the atmosphere. But this can only be achieved in the presence of heat, moisture and light.

When the cold comes, plants with active working leaves are susceptible. Because photosynthesis requires a constant, large amount of water. When air and soil temperatures drop, cold kills unprotected plants, turning water in their cells into ice.

To prevent this, the plant gets rid of excess water and sheds its leaves, which in order to adapt to climate change. In this way, the leaf shedding protects the plant from dehydration. It can be seen that the shedding of leaves in autumn is a method used by plants to protect themselves.

Autumn is an extremely important time for life in nature to recuperate, and leaf fall is also a kind of preparation for the normal growth of trees in the coming year.

As spring turns to autumn, nature adds new clothes, and the leaves change from green clothes to yellow and gold, and even dance in bright red dresses. Turns out this is the function of making food with leaves? Photosynthesis is related.

Photosynthesis is when plants absorb sunlight and subtly convert carbon dioxide from the air and water from the soil into nutrients. In order to photosynthesize, leaves produce chlorophyll to absorb sunlight.

In fact, there are many different pigments in leaves, in addition to chlorophyll, lutein, carotene, etc., but when the leaves are photosynthesized, a large amount of chlorophyll will be produced.

In winter, when temperatures drop and the weather is drier and even freezes in some areas, plants stop photosynthesis for a while and suck nutrients from the leaves back into the stems for storage. Since the leaves stop photosynthesis, they no longer produce chlorophyll, and the original chlorophyll is slowly destroyed and disappeared due to the low temperature. Other pigments that would otherwise be hidden in the leaves, such as yellow, will appear.

Some leaves turn red because in the fall, they produce red anthocyanins. Regardless of the color, the leaves will wither and fall in autumn as they lose their function as a nutrient.

The ground has become dry, and the ability of the roots to absorb water has weakened, and they cannot supply the tree with as much water as they do in the summer. The water in the body of the tree is mainly run out through the leaves, and if the leaves of the tree are still retained, too much water will run away, and the tree will die due to lack of water. Therefore, the tree sheds its leaves to protect itself, so that it can rest for a while in the harsh climatic conditions, and then sprout and grow leaves again when spring comes.

Leaves are dropped to reduce nutrient consumption.

Because autumn does not have enough temperature, moisture and sun.

Because the weather becomes drier in autumn, trees retain water in their bodies (excluding bark) in order to conserve water, leaves lack water and nutrients (nutrients are transported by water), leaf cells gradually die (chlorophyll also slowly disappears), leaves (including petioles) without water slowly dry out, the connection between the petiole and the trunk will be unstable, and the leaves will fall through the action of external forces (in the wind).

People often use the phrase "autumn wind sweeping away the leaves" to describe the autumn scenery in temperate regions. When autumn arrives, the leaves of broad-leaved trees such as poplars and locust trees gradually age, and with the autumn wind, the yellow leaves quietly fall. You may feel sorry for the falling leaves, but have you ever thought that falling leaves are precisely the self-protection of trees?

When it was cold, people lit stoves and put on cotton clothes. But what about the trees? They can only survive the winter safely by stripping their leaves to minimize water transpiration.

Otherwise, it is already difficult for the roots to absorb water, but the transpiration of the leaves continues as usual. Think about it, what awaits the trees but death?

The petioles originally grew stiffly on the branches. In autumn, as the temperature drops, several layers of fragile parenchyma cells form at the base of the petioles. Because these cells are easily separated from each other, they are called delamination.

When the separation layer is formed, it breaks if it is blown by a slight breeze, and the leaves fall down.

Leaves are broad-leaved trees in temperate regions, reducing transpiration and preparing for a safe winter.

When the temperature drops, the growth of the tree stops, and it enters a state of "hibernation", and the leaves do not need to photosynthesize, wither, die, and wither.

Autumn leaves fall for trees to survive the winter, because there is less water in winter, and falling leaves can reduce water consumption.

This is the method of self-protection taken by plants in the face of external environmental changes, usually this kind of plant leaves do not have a waxy layer or only a very thin waxy layer, the water retention is slightly poor, in order to slow down the consequences of water and nutrient supply caused by metabolism, in addition to the leaf water content, low temperature may frostbite the leaves, so the plant will secrete abscisic acid, promote its own leaves to fall, after the defoliation will reduce the demand for nutrients and water in the plant body, the whole plant is in a dormant state, in order to better survive the cold winter.

The laws of the plant's own development and metabolism.

1. The plant's own protection mechanism, the temperature drops, the root water absorption and mineral ability decreases, the defoliation decreases, the transpiration light is weak, the photosynthetic products are reduced, and the photosynthesis and respiration in the leaves are the same in the deciduous deciduous, reducing nutrient consumption.

2. Hormone action, the accumulation of abscisic acid at the petiole, and the physiological and structural changes of the cell lead to the formation of delamination, which is easy to fall off.

3 Life cycle, determined by genetic material, is affected by the environment.

The main use of green leaves is to absorb sunlight, photosynthesize, produce nutrients, and transpire water. Transpiration of water keeps trees from being burned in blazing sunlight. In autumn and winter, when rain is scarce and the air is dry, the moisture content of the soil also decreases, which cannot meet the needs of tree growth.

At this time, a hormone, abscisic acid, is produced in the leaves. When the abscisic acid in the leaf is transported to the base of the petiole, a layer of very small parenchyma cells with a very thin cell wall will be formed at the base of the petiole, and the formation of the delamination will make the water can no longer be transported to the leaf normally. Under the action of abscisic acid, a natural section will be formed around the separation layer, and the leaves will fall off.

Autumn leaf litter reduces water transpiration and nutrient consumption, allowing trees to survive the cold, dry winter safely.

Hello That's because autumn means the coming of winter, trees need to be dormant for self-protection, and overwintering dormant trees themselves also need nutrients, in order to regulate their own homeostasis, many trees need to fall leaves, reduce the loss of water's nutrients, save energy and wait until the conditions are right before germinating from scratch. This is a kind of adaptation of these plants to the cold. In winter, due to the cold, various metabolisms of plants are slowed down.

Defoliation is done to reduce the transpiration of the leaves to water. This can not only keep the plant with enough water in the body, but also reduce the heat loss in the plant body, so that the plant can survive the harsh winter.

Because there is not enough water and sunlight in autumn, the leaves will fall.

Because the man dialed the leaf....