Why do the leaves fall? Why do the leaves fall

There are two kinds of leaf loss of trees: one is that whenever the cold season comes, the leaves of the whole tree die and fall off at the same time, and only bald branches remain; The other is that after the new leaves grow in spring, the old leaves gradually wither, and the fallen leaves are not concentrated in a period, and the trees are green all year round from the appearance, so they are called evergreen trees. Such as pine and cypress.

The defoliation of trees is the result of a combination of internal and external factors. The internal reason is that after a certain period of physiological activities in the leaves, a large number of metabolites accumulate in the cells, causing the decline of leaf cell function, aging, and death; The external reason is that due to the cold climate, there are two situations of leaf loss of the tree: one is that whenever the cold season comes, the leaves of the whole tree die and fall off at the same time, and only the bald branches remain; The other is that after the new leaves grow in spring, the old leaves gradually wither, and the fallen leaves are not concentrated in a period, and the trees are green all year round from the appearance, so they are called evergreen trees.

Such as pine and cypress. The defoliation of trees is the result of a combination of internal and external factors. The internal reason is that after a certain period of physiological activities in the leaves, a large number of metabolites accumulate in the cells, causing the decline of leaf cell function, aging, and death; The external cause is due to the cold climate.

I hope you are satisfied!

Is this a physical problem, or a biological problem, or a literary problem?

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.

Of course, the reason why it falls down and not up is because of the gravitational pull of the earth on it.

When a leaf falls, you know the autumn of the world".

Because of gravity! Attracted to it by the Earth!

<> due to the shortening of sunlight and the lack of water due to the decrease in temperature, abscisic acid in the plant will be produced in large quantities, so the leaves will fall off. Tree defoliation is also a form of self-protection, the leaves emit water, the leaves are dropped to retain moisture, and then the tree goes into hibernation to get through the winter safely.

The leaves will fall because autumn is coming, due to the shortening of the sunshine and the decrease in temperature, the water ** is insufficient, and the abscisic acid in the plant will be produced in large quantities, in order to reduce the transpiration of water, the trees can get rid of the leaves of the whole body in the autumn to survive the winter safely. This is a normal physiological phenomenon of trees, and it is also an adaptation of trees to adverse climatic conditions such as low temperature and drought.

Leaves are the part of the tree that undergoes photosynthesis, and the leaves can come in a variety of shapes, sizes, colors, and textures. The leaves can be clustered together or scattered all over the place. The edges of the leaves can be smooth or jagged.

Leaf support – protects young leaves. Some plants do not have a leaf support, and some plants have a leaf that falls off very early.

Leaves are the main organs of plants for photosynthesis and nutrient production. By absorbing carbon dioxide, oxygen is released (release place: stomata), food is provided, and shelter from the wind and rain. Leaf photosynthesis is done through chloroplasts.