Why do leaves turn yellow in autumn?

In autumn, the leaves will turn yellow because the pigments in the leaves have changed. In fact, there are many pigments in leaves, besides chlorophyll, there are carotenoids and lutein and so on. When the leaves are growing, the green color in the leaves is dominant, chlorophyll is synthesized in plants, and photosynthesis is more active. But in autumn, because the days are shorter, the nights are longer, and the sunshine time of plants is shorter, the photosynthesis is reduced. Therefore, carotenoids and lutein in plants begin to dominate, and chlorophyll becomes less, so the leaves will turn yellow slowly.

The pigment in leaves actually represents the pigment when plants display colors. When there is more pigment, the leaves will show a color. However, generally speaking, the photosynthesis of growing plants is very active, so there is a lot of chlorophyll in the body. Therefore, generally, the newly grown plants will appear green, but when the plants are aging, photosynthesis will slow down and chlorophyll in the body will decrease, which will naturally wither and turn yellow.

Color of leaves Sometimes the leaves will not appear pure green or pure yellow, but the middle color, and some will appear red. In fact, this is also because plants are affected by temperature, air temperature and sunshine time during their growth. If there is only lutein in plants, they will show pure yellow leaves like ginkgo. But if there is only chlorophyll in the plant, it will appear green.

However, when the weight of lutein and chlorophyll is similar, or the difference is not particularly great, it will present an intermediate color. With the gradual increase or decrease of pigment content, it will present different colors with the change of pigment. Of course, the more pigment content, the more prominent and obvious it will be.