It is said that the first frost kills a hundred herbs, and some people say that frost can't hurt crops, but it will protect them. What's going on here?

The first frost is the last solar term in autumn. Gregorian calendar 10 every year 10 on 23rd or 24th, when the sun is at 2 10 degrees, it is the first frost. The first frost means that the weather gets cold and frost begins to appear.

In ancient China, the first frost was divided into three stages: "The jackal is a sacrificial animal, the flowers and trees are yellow, and the stinging insects are salty." In this solar term, jackals catch prey and begin to prepare for winter; The leaves on the earth are yellow and withered; The stung insects are still in the hole, ready to go into hibernation.

"The first frost kills a hundred herbs" means that all kinds of plants that have suffered severe frost will lose their vitality. This statement makes sense, but it is not accurate. Herbs lose their vitality because the liquid in plants forms ice crystals due to frost, which leads to protein deposition in cells and water extravasation, which makes protoplasm seriously dehydrated and deteriorated. But it is "freezing" rather than "frost" that does harm to plants.

Although frost and frost are closely related, they cannot be confused. Someone once tried to put two leaves of a plant, one frosted and the other unfrozen, in boxes at the same low temperature. Results The leaves in frost-free period were seriously damaged, while those in frost period had only slight traces of freezing injury.

Facts have proved that frost not only does not harm crops, on the contrary, when water vapor condenses, it will release a lot of heat, thus avoiding the freezing injury of plants. It is not so much "the first frost kills a hundred herbs" as "the frost kills a hundred herbs".

What is "frost"? When the air temperature on the ground or near the ground drops below 0℃, the water vapor in the air near the ground will condense into white crystals similar to the ice cubes on the surface of the ground and ground objects. This crystal is called frost. Frost itself has no direct effect on crops, but the low temperature during frosting will cause crop freezing damage.

So what is frost? The key to understanding frost is "freezing", not "frost". "Frost" is a weather phenomenon in which the temperature near the ground drops below zero degrees Celsius and plants are frozen.

When there is frost, if the ambient temperature is not too low, or the crops have strong cold resistance, the crops may not be frozen. On the contrary, without frost, crops may be hurt.

On the one hand, this may be because tropical and subtropical crops will be frozen when the temperature is not very low; On the other hand, it may be because there is too little water vapor in the air. Although the temperature has dropped below 0℃, there is no frost.

In a word, frost will cause freezing damage to crops, not because of frost, but because the temperature is lower than the minimum temperature limit that crops can tolerate when there is frost, thus causing crops to suffer.

Summary: The first frost, the bleak earth, easily produces the feeling of sad autumn, which makes people depressed and demoralized. This state is very unfavorable, so we must adjust our mood, participate in some recreational activities that are beneficial to the body and mind, communicate with people more in the first frost season, and enhance people's resistance from the inside out.