Why do leaves turn yellow in winter?

In autumn, the green pigment slowly fades away, and the red and yellow pigments are exposed. All leaves contain green chlorophyll, which trees use to capture light energy and store it in the form of chemicals such as sugar with the help of other substances in the leaves.

In addition to chlorophyll, many leaves also contain other pigments such as yellow, orange, and red. Although these pigments cannot perform photosynthesis like chlorophyll, some of them can transfer captured light energy to chlorophyll.

In spring and summer, the content of chlorophyll in leaves is much more abundant than other pigments, so the leaves show the green color of chlorophyll, and the colors of other pigments cannot be seen.

Extended information:

Chlorophyll, the main pigment for photosynthesis in plants, is a family of lipid-containing pigments located in the thylakoid membrane. Chlorophyll absorbs most of the red and violet light but reflects green light, so chlorophyll appears green. It plays a central role in light absorption during photosynthesis.

Chlorophyll is a magnesium porphyrin compound, including chlorophyll a, b, c, d, f, protochlorophyll and bacteriochlorophyll. Chlorophyll is not very stable and will be decomposed by light, acid, alkali, oxygen, oxidants, etc.

Under acidic conditions, chlorophyll molecules can easily lose the magnesium in the porphyrin ring and become pheophytin. Chlorophyll has many uses such as hematopoiesis, vitamin provision, detoxification, and disease resistance.

Reference: Baidu Encyclopedia----Chlorophyll