The reason why maple leaves turn red:
Stress response: The red maple leaf is actually the maple tree's response to natural stress. The red maple leaf actually acts as a sunscreen, making the leaves stay on the tree for a longer time and allowing the tree to absorb more nutrients. It is found that the pressure of nutrition, especially the pressure of lack of nitrogen, makes the maple leaves turn red earlier and more thoroughly.
Internal factors: There are two main substances that make leaves appear red. One is carotene, an orange-red pigment commonly found in chloroplasts. The other is anthocyanin, which exists in the cytosol of vacuoles. When the cytosol is alkaline, anthocyanins are blue-purple, and when the cytosol is acidic, anthocyanins are red. After autumn, the anthocyanins in cotinus coggygria leaves increased, and the chlorophyll destruction disappeared due to the decrease of temperature, so the green leaves turned red.
The degree to which maple leaves turn red is related to time, drought, pollution, especially nitrogen deficiency. The red maple leaves are actually the result of maple trees responding to natural pressure. The red reaction actually acts as a sunscreen. It makes the maple leaf stay on the tree for a longer time and makes the tree absorb more nutrients. It is found that the pressure of nutrition, especially the lack of nitrogen, makes the maple leaves turn red earlier and more thoroughly.
Maple leaf is a maple leaf, which is generally palmately divided, about 13cm long, slightly wider than the palm of an adult. Lobes have several prominent teeth, the base is heart-shaped, the leaves are rough, the upper part is medium green to dark green, the lower veins are hairy, and they turn yellow to orange or red in autumn. But a few areas are dark green.