Leaves are important to plants and trees because they convert sunlight energy into food through a process called photosynthesis. Leaves have a chemical called chlorophyll in them, which is what allows them to photosynthesize.
Leaves go through seasonal changes, which include:
- Changing color
Leaves change color in the fall because as temperatures cool, the chlorophyll in the leaves starts to break down, which signals to the tree that it needs to store the converted food in the tree, rather than in the leaves. The leaves change color because of the lack of chlorophyll, which is what makes the leaves green in the spring and summer months. The changing color depends on the presence of carotenoids or anthocyanins. Carotenoids are the chemicals that turn leaves brown, orange and yellow, whereas anthocyanins are the chemicals that cause leaves to turn purple or red.
Deciduous trees lose their leaves in autumn because as temperatures fall, the trees create a seal between the branch and its leaves that protects the branches from the freezing temperatures of winter. Evergreen trees, on the other hand, have needles instead of leaves, which are able to withstand the freezing temperatures because of their waxy coating. Needles remain green all year and do not change color or fall off.