Why do maple leaves turn red? The latest explanation is here

The biggest impression maple leaves make on people is that they turn red. Writers and scholars through the ages have been especially fond of maple leaves, and poems and prose praising and depicting them are common, such as the Tang poet Du Mu's “Stopping the carriage to enjoy the maple grove at dusk, frost-bitten leaves are redder than February flowers.” and so on. The beauty of maples has been widely recognized by people through the ages, and maples planted in gardens and scenic spots everywhere are also relatively common. Below, let us take a look at why maple leaves turn red!

When do maple leaves turn red?

Maple leaves turn red in autumn. Maple leaves turn red in autumn because falling temperatures cause the green pigment in maple leaves to turn red. In northern China, autumn runs from August to October, and true autumn generally does not begin until after September, so maple leaves usually do not turn red until around September or October. In southern China, the cold comes later, so maple leaves turn red relatively later.

When do maple trees shed their leaves?

Maple leaves fall in autumn. When autumn arrives, days shorten and nights lengthen, the weather turns cold, soil temperature drops, rainfall decreases, the root system's ability to absorb water is greatly weakened, while transpiration intensity does not weaken, and water shortage causes leaf fall. At the same time, after a certain period of physiological activity, large amounts of metabolic products in the leaf cells, such as accumulated minerals, cause physiological function to decline and death (destruction of chlorophyll).

Why do maple leaves turn red?

1. Stress response: Maple leaves turning red is in fact the result of the maple tree's response to natural stress. Turning red actually acts as a sunscreen, allowing the leaves to stay on the tree longer and letting the tree absorb more nutrients. Research has found that nutritional stress, especially nitrogen deficiency stress, makes maple leaves turn red earlier and more thoroughly.

2. Internal factors: The red color of leaves mainly depends on two substances. One is carotene, an orange-red pigment commonly present in chloroplasts. The other is anthocyanin, which exists in the cell sap within vacuoles. When the cell sap is alkaline, anthocyanin appears blue-purple; when the cell sap is acidic, anthocyanin appears red. After autumn begins, anthocyanin in the leaves of smoke tree increases, while falling temperatures destroy and eliminate chlorophyll, so green leaves become red leaves.

3. External factors: When the temperature drops rapidly to a certain degree, and the nighttime temperature falls much more than the daytime temperature, the leaves have not yet fallen, while most of the chlorophyll has already been destroyed. At the same time, the increase in the temperature difference between day and night also helps the formation of anthocyanin, so the leaves quickly turn red. If the temperature drops very slowly, and the temperature difference between day and night is not large, the chlorophyll has not yet been destroyed while the tree has already withered, then it cannot become beautiful red leaves.