Why do apples turn red in autumn?

The reddening of apples is related to pigments, which can make plants red.

There are two main reasons for the discoloration of apples: one is internal factors. Apples contain a red pigment or a green pigment. When the red pigment increases, it appears red, and when the green pigment increases, it appears green.

Secondly, external factors, mainly the role of sunlight, when the sun shines on the apple, the red pigment on the illuminated surface will increase greatly. In this way, the sunny side of the apple will gradually turn red, on the contrary, the other side will appear greener.

Why does autumn turn red? It is because in autumn, the red pigment of apples accumulates to a certain amount, so it gradually becomes more and more red.