Question

What chemical change causes leaves change color in autumn?

Answer 1

Hint : Autumn is a season which is just the transition of the weather, that is, from summers to winters. In the autumn season, we get less of daylight and more of the nightlight. This change in the timing effects a lot, from animals to plants.

Complete Step By Step Answer:
Now, we know that each and every plant has chlorophyll
(${C_{55}}{H_{72}}{O_5}{N_4}Mg$), that’s why they show green coloration. So, when there is a breakdown of chlorophyll, the green color of the plant will disappear and instead of green color we will observe different colors varying from yellow to orange and we observe these colors due to the presence of certain pigments called carotenoids pigment (${C_{40}}{H_{56}}$) and xanthophyll pigment (${C_{40}}{H_{56}}{O_2}$). Also, in the autumn season we often observe red colors in the leaves of the plants which is due to the formation of a red colored pigment which is known as anthocyanin.
As we know, there is a change in the length of day and night and also there is a change in the temperature, so the leaves of the plant stop their photosynthesis, that is, their food making process, in which there is release of oxygen and intake of carbon dioxide. So due to these changes, chlorophyll breaks down and the green color disappears and instead of green color we observe a range of colors, ranging from yellow to orange and from orange to red due to the presence of certain pigments as mentioned above.
So, as we can see the weather affects a lot, such as temperature, length of the day and length of the night, water supply, intensity of the color, and so on and due to these changes such type of phenomena occurs.
For example: when the temperature is low, we can see bright red colored leaves of the plant and that happens because the formation of anthocyanin pigment occurs favorably at low temperature.

Note :
Hence, we can say that, during the autumn season, green colored leaves disappear due to the breakdown of chlorophyll which occurs because of more darkness and less daylight which makes the leaves stop their photosynthesis process.