Meteorological significance of winter

The first day when the average daily temperature is lower than 10℃ for five consecutive days is the meteorological winter.

astronomy

In winter, the direct point of the sun moves south to the tropic of Capricorn, and then turns back to the north. Squirrels dig holes near winter to bury the food they find, and then sleep in tree holes in winter. When they are hungry, they get up and dig out the food buried in the ground to eat.

In addition, they can put eighteen pine nuts in their cheeks, fill them first, and then go to bed.

But their food is often dug up and buried by other peeping squirrels, and sometimes they forget what they buried. Cute, isn't it?

Insects are warm animals. How do they spend the winter? It turns out that they each have a set of tricks.

Mantis can be made into large eggs, each with 300 to 400 eggs, which together with secretions form oocysts. Outside is a thick protective layer, attached to the trunk of the sun, not afraid of snow, ice and cold wind.

Negative worms lay eggs on their backs and then lurk in underwater soil for the winter.

Leaf-cutting bees transport piles of oval leaves into underground or hollow wood to build rows of beehives and form oval "houses". There is nectar or pollen in the house to lay eggs for winter. Each leaf cutter can build 30 hives, and it needs at least 1000 oval leaves. This project is great.

Larvae of scarab, obese and nutritious, hibernates in the deep soil.

The longicorn beetle was born with a sharp mouth, and dug a "tunnel" on the trunk, in which its larvae spent the winter.

There is a hard chitin shell outside the pupa of moth, which can bear the cold attack, and more fat is stored in the pupa, which can prevent frostbite.

From the larval stage, the debt-avoiding moth makes a "pocket" with bark and branches, carries it on her back or hangs it on the branches, and hides it in the "pocket" when she is at rest. In late autumn, I got into my pocket, turned into a pupa, and passed the winter safely.

In the deep winter festival, bees not only eat stored honey to get heat, but also "crowd together" around the queen bee to form a hive, so as to keep the temperature in the hive at about 35℃. If the bees in the outer layer are too cold to stand, they will "change their defenses" inside and outside. For those larvae, worker bees will feed 1300 times a day like competent nannies. At the same time, worker bees also gather together to form an insulating layer to protect the larvae from the cold. If the larvae still feel cold, the worker bees will spread their wings and dance to raise the temperature of the hive.

The wasp has amazing cold tolerance and is still safe at -47℃.

Scientists have found that there is a special pigment cell in the "skin" of cold-resistant insects. The size of this pigment cell can be changed at any time. When the cell membrane is enlarged, the skin color becomes lighter, which makes the insect's body reflect light well; When the cell membrane contracts, the skin becomes darker and the body can absorb more light and heat. If the body is too hot, the pigment cells in the insect will swell to prevent the body temperature from rising excessively.

The mother grasshopper digs a hole with a hard "tail" (spawning flap) on the leeward slope of Chaoyang, then puts her belly into the hole, puts the eggs together one by one, and then secretes glue to wrap the eggs, just like a plastic bag, which is both warm and not afraid of blisters. It is really foolproof.

Cicada's oviposition tube is like a saw, which is used to cut the bark, lay eggs in it and let the eggs spend the winter in the bark.

Blind stinkbug's mouth is like a needle. It first pricks a small hole in the plant with its mouth, then turns its head and puts the ovipositor in the small hole to lay eggs. There is a small cover at the exposed end of the egg, which can prevent wind and air, killing two birds with one stone.

Before winter comes, moth larvae go underground to make a solid earthen house, and then spit out mucus from their mouths to paint the inner wall, making the "small earthen house" smooth, warm and safe.

Wheat sawfly can't build a house, but it knows it's too dangerous to sleep in shallow soil, so it goes to deep soil, which is not only warm, but also inaccessible to farmers when they plough the land next year.

Moth larvae have another skill. It spits out silk and mucus, and weaves wool into a hard cocoon, just like a bird's egg, which sticks to the branches and is as hard as a small stone head. No one can eat it if they want.

Li Xing caterpillars like to eat buds in early spring. They climbed to the sunny side of the trunk of the old tree, drilled into the cracks and holes of the old tree, and then took off their long hair, and spun silk was woven into a "blanket" and wrapped tightly around them to avoid freezing.

The beetle's hard wing sheath and thick skin are like wearing a winter coat. When winter comes, they eat, drink and store enough nutrients in their bodies. Therefore, they are least afraid of the cold and can safely spend the winter in hidden corners under fallen leaves, gravel and tree holes.

Houseflies bury their pupae in the soil for the winter, but most flies and mosquitoes spend the winter as adults. They sneak into people's houses and hide in dark corners, all of which can survive the winter safely.

Bean moths and Pieris rapae spend the winter in pupae. Pupa skin is thick and hard, and it is more cold-resistant than larvae. As soon as the weather gets warmer, winter pupae turn into butterflies flying in the fields.

Insects should be fully prepared for safe winter. If carefully observed, it is not only interesting, but also helps us to eliminate pests and protect beneficial insects!

The city is full of traffic and the zoo is very lively. Siberian tigers, jaguars, snow foxes ... animals in cold regions are playing in the snow. While giraffes, elephants, zebras and other tropical animals hide in houses with heating and air conditioning for fun.

Winter is cold, and all kinds of plants can still survive the cold winter and continue to grow, blossom and bear fruit in the coming year. Where is the mystery?

It turns out that before the cold comes, plants make various physiological adaptive responses: for example, the increase of soluble sugar content can increase the concentration of cell solution and reduce the water point. It can also buffer the excessive dehydration of protoplasm and protect protoplasm colloid from cold solidification. In addition, sugar molecules have great surface activity, which can be adsorbed on the surface of organelles and weaken their vitality. There is more sugar in the cell, the osmotic pressure increases, and more water is retained, which reduces freezing when going out. Other plants adapt to low temperature conditions by reducing their own water content and spend the cold winter safely.

When the temperature drops to about 5 degrees in winter, the aboveground growth of winter wheat basically stops, but photosynthesis continues slowly. At this time, the synthetic products are not converted into starch or other insoluble substances, but accumulated in the cells in the form of soluble sugar (mainly glucose). In winter, chlorophyll formation of wheat seedlings is less, and the cells are neutral or slightly acidic. At this time, the color of wheat seedlings began to turn red, which is a sign of strong cold resistance and normal growth of wheat seedlings.

The flower buds of fruit trees can survive the winter safely, so that the next year will be full of flowers and fruitful results. This mainly depends on the change of water content in flower buds. When the temperature drops, the flower bud quickly discharges the water inside, so that the juice in the flower bud reaches a high degree of contraction. This kind of high juice has strong frost resistance and will not freeze in severe cold, thus preventing the cell membrane from breaking due to freezing. Even if the temperature drops to MINUS 30 degrees, the cells in the flower buds can still be safe and sound. 1. adaptive physiological and biochemical changes of plants at low temperature

Before the arrival of winter, with the shortening of sunshine and the decrease of temperature, plants will undergo a series of physiological and biochemical changes to adapt to the low temperature, thus improving the quality of plants.

Improve the cold resistance of plants.

This adaptive process of gradually improving cold resistance is called cold exercise or cold domestication.

Plants are vulnerable when cold waves suddenly attack them in late autumn or early spring.

After proper cold-resistant exercise, plants gradually complete a series of metabolic changes to adapt to low temperature and gain strong cold-resistant ability.

In late autumn in northern China, the cold-resistant exercise in plants has not been completed yet, and the cold resistance is poor; In early spring, the temperature rises, and the cold resistance of plants gradually decreases.

Adaptive physiological changes of plants in cold-resistant exercise

(1) The water content of tissue decreases, while the relative content of bound water increases.

(2) The decrease of respiration and consumption is beneficial to the accumulation of sugar, the overall metabolic intensity of plants is weakened and the stress resistance is enhanced.

(3) With the increase of ABA content, the growth stopped and went into dormancy.

The nuclear membrane mouth of winter wheat is gradually closed, the material exchange between nucleus and cytoplasm stops, cell division and growth activities are inhibited, and plants enter dormancy.

After plants enter deep dormancy, their cold resistance is obviously enhanced.

ABA content

(4) the accumulation of protective substances

The content of soluble sugar increased, which protected the living body and biofilm of cells.

It can increase the concentration of cell fluid, reduce the freezing point, improve the water-holding capacity of protoplasm, and protect protein colloid from cold denaturation and solidification; Can be further transformed into other

Protective substances (such as phospholipids and amino acids). ) and energy.

In cold-resistant exercise, the content of amino acids also increased.

Proline content increases more obviously, and it is an antifreeze or membrane stabilizer, which plays an important role in adapting plants to various adversity.

2. Cold inducible protein.

Plants induced by low temperature can activate some specific genes, express and synthesize a new set of protein.

Nearly 100 kinds of plant cold-induced proteins have been found and studied, but the mechanism of improving plant cold resistance is still unclear.

Antifreeze protein AFP (antifreeze protein AFP)

It is a glycoprotein contained in the blood of fish living in polar ice water, which can lower the freezing point of intercellular body fluids.

Plants themselves may also have antifreeze proteins similar to those of animals, and their antifreeze ability based on similarity principle.

Arabidopsis thaliana cold regulatory protein COR6.6 protein.

Rape BN28 protein

Arabidopsis chloroplast COR 15 protein

Late embryogenesis rich protein (LEA)

In the later stage of embryonic development, when seeds are dehydrated, plants produce a lot of protein.

Most of them are soluble protein which is highly hydrophilic and stable in boiling water.

Plants can also express a variety of LEA proteins under low temperature induction.

It is helpful to improve the ability of plants to withstand dehydration stress during freezing and reduce the dehydration of cells during freezing.

Most LEA proteins can also be induced by drought or exogenous ABA.

3. Measures to improve the cold resistance of plants

Start from two aspects:

Improve the cold resistance of plants themselves

Change the microclimate of plant growth

(1) cold-resistant exercise

By artificial or natural methods, germinated seeds or seedlings are treated at moderate low temperature to improve their cold resistance.

After cold-resistant exercise, the resistance is enhanced.

With the increase of sugar content in cells, the ratio of bound water to free water increases, the viscosity and elasticity of protoplasm increase, and the metabolic activity decreases.

(2) Chemical control

Growth retarder AMO- 16 18, paclobutrazol.

Widely used for dwarfing fruit trees and promoting flower bud differentiation.

It can inhibit gas synthesis and improve the cold resistance of trees.

Exogenous ABA treatment

It can improve the cold resistance of plants at room temperature, and at the same time induce the expression of various low-temperature inducible genes to produce low-temperature inducible proteins.

(3) Other agricultural measures

Cultivate cold-resistant varieties

Improve the soil temperature of overwintering and early spring crops and protect plants from freezing injury.

Sow in time, cultivate the soil and increase the application of phosphorus and potassium fertilizer, especially organic fertilizer and green manure.

Before the cold current frost comes, do a good job in plant protection such as smoking, winter irrigation and grass cover.

Use plastic film seedbeds and mulches.

Protect spring-sown crops from the cold current in early spring