Why do plants lose their leaves in winter, but some don t?

Let's start with popular science: Plants that don't seem to lose their leaves in winter are actually losing their leaves.

Plants lose their leaves in winter because the roots of the plant are dormant in winter and absorb very little water, and in order to reduce transpiration (evaporation) of water, the organ leaves that transpire water fall off.

Plants that don't seem to lose their leaves are also losing their leaves in small amounts, and new leaves grow quickly.

The reason is as follows: the leaves will naturally fall off after a certain period of life, and this phenomenon is called falling leaves. There are two cases of leaf litter of woody plants:

1. One is that the leaves only live in one growing season, and whenever winter comes, they fall off in full sales, which are called deciduous plants, such as willow, etc.;

2. The other is that the leaves can live for two to many years, and fall off at the last time in the plant, as far as the whole tree is concerned, it is evergreen all year round, called evergreen plants, such as pines and cypresses;

Leaf shedding can reduce water loss, late autumn or dry season, can be seen as an adaptation of plants to avoid excessive transpiration, but some trees can reduce transpiration due to their special structure, as follows:

1. The leaves of pine trees are needle-like, also known as pine needles, which reduce the transpiration area, the epidermis is thick, and the cuticle is developed, these structures can reduce transpiration and adapt to the arid environment, so they are evergreen all year round;

2. There is a thick cuticle on the leaves of boxwood and other plants, and there is wax on it, so it can also reduce transpiration and be evergreen all year round.

Most of the green-leaved trees need to be dormant for self-protection, and the 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, and save energy until the conditions are suitable before sprouting.

When winter comes, the temperature drops, the chlorophyll that carries out photosynthesis is destroyed, and the cells do not have enough nutrients and die, and the cells lose their viscosity after death, and the leaves fall due to gravity or wind.

Plants that do not lose their leaves in winter include camphor, cedar, dragon cypress, masson pine, large-leaved boxwood, oleander, camellia, coral tree, geranium, etc., among which camphor is an evergreen large tree plant, its leaves are green all year round, and cedar is an evergreen tree of the pine family, its cold tolerance is strong, and its leaves will not fall in winter.

1. Camphor

Cinnamomum camphora is an evergreen tree of the Lauraceae family, it will not drop its leaves in winter, its leaves are green all year round, and camphor is mainly distributed in Fujian, Jiangxi, Taiwan, Sichuan and other places in China, it has no strict requirements for soil, and can grow in clay loam, sandy loam, acidic soil or slightly alkaline soil.

2. Cedar

Cedar is an evergreen tree of the genus Cedar of the Pinaceae family, its leaves are needle-shaped, the length is 8-60 cm, the color is gray-green or silver-gray, and the cold tolerance of cedar is strong, it usually grows in the area of 1300-3300 meters above sea level, mainly distributed in Beijing, Hangzhou, Changsha and other places in China.

3. Dragon cypress

Dragon cypress is a plant that does not lose its leaves in winter, it is an evergreen tree belonging to the cypress family, the height can reach 21 meters, the pH of the soil is adaptable, when breeding dragon cypress, it needs to provide fertile and deep soil, and to apply enough base fertilizer to the soil to promote the vigorous growth of dragon cypress.

4. Masson pine

Masson pine is an arbor plant of the pine family, the height can reach 45 meters, the bark is reddish-brown, its leaves will not fall off in winter, and the distribution range of Masson pine is wider, it is distributed in the area of 600-1500 meters above sea level, and the growth rate of Masson pine is fast, it is the main wood tree species in China.

Whether a tree is defoliant or not is determined by its long-term evolutionary evolution and adaptation to the natural environment. Deciduous tree species fall defoliation because of the need to resist adverse environmental factors, such as falling leaves in winter, in order to reduce water evaporation, so that the cytoplasm in the body from liquid to colloidal transformation to enhance its resistance to stress, so as to survive the cold winter, when the plant is shed, the plant hormone abscisic acid in the body produces the effect of changing the separation layer between the leaves and the plant body. Separation occurs between cells, and as a result, leaves fall off.

First of all, pines and cypresses are not leafless! The leaves of plants have a certain life period, generally speaking, the leaf life period is only a few months, and there are also those that can live for two to several years. Leaves fall off naturally after a certain period of life, a phenomenon called leaf fall.

There are two kinds of deciduous leaves of woody plants: one is that the leaves only live for one growing season, and every time winter comes, they all fall off, which is called deciduous plants, such as willow and so on; The other is that the leaves can live for two to many years, mostly in spring and summer, after the new leaves occur, the old leaves fall off in the last plant, as far as the whole tree is concerned, it is evergreen all year round, called evergreen plants, such as pines and cypresses. Leaf shedding reduces water loss, and late autumn or dry season leaf shedding can be seen as an adaptation of plants to avoid excessive transpiration.

The leaves of the pine tree are needle-like, also called pine needles, and the leaves of the cypress tree are flattened, these structures reduce the transpiration area, the epidermis is thick, and the cuticle is developed, these structures can reduce transpiration and adapt to the arid environment, so they are evergreen all year round.

It depends on the ambient temperature of the outside world, falling leaves.

Plants are basically concentrated in temperate and cold zones, and the temperature drops in winter, and deciduous plants do not contain ingredients that can act as antifreeze, so in order to prevent frostbite, the method of defoliation is adopted. Conifers containing pine oil and other antifreeze ingredients do not need to fall leaves, as for warm areas, there is no frost damage, and plants do not need to fall leaves for normal growth. Therefore, once the cold snap passes in the south, the plants freeze to death, and the north rarely appears.

Due to the low temperature in winter, many nutrients cannot be adsorbed from the roots, and the leaves cannot withstand the low temperature, and the nutrients cannot reach the leaves, and finally the leaves dry up and fall.