Why do leaves turn upside down at the beginning of autumn?

Because the leaves of trees are composed of cells, the cells near the leaves are dense and have a large proportion; The cell structure near the leaf back is loose and the specific gravity is low. Because of gravity, when the leaves land, they land before the important side (that is, the leaf surface), and the back of the leaves is upward. In the process of falling, a few fallen leaves are affected by wind, and the leaves are upward.

Beginning of autumn is the13rd solar term among the 24 solar terms in the lunar calendar, and it is also the first solar term in autumn, which marks the official start of the Meng and autumn seasons: "Autumn" means that summer is cool. When we arrived in early autumn, the phoenix tree began to shed its leaves, so there is an idiom "Leaves fall to the roots". Literally, the word "autumn" consists of "valley" and "fire", indicating the maturity of five grains. Autumn is the transitional season when the weather turns from hot to cold, and then from cold to cold. ?

Beginning of autumn, July Festival. Make a word to understand spring. In autumn, things are different here. ?

At the beginning, a cool breeze came. The bleak wind in the west is called cool wind. The temperature changed and the chill began to subside. "Zhou Yu" said that it is also true that the eyes are golden and the breeze is cold. ?

Wait, the Millennium falls. After the heavy rain, the cool wind came and the weather dropped. Those white beads have not yet condensed, so the white dew drips, showing the white of autumn gold. ?

Third class, chilling. Chilling, "Erya" said chilling, small and green; Ma Shi said that things were born in the heat and their voices changed.