What Makes the Leaves Turn Colors in the Fall?

Leaves change colors in the fall when they lose their chlorophyll.

Days get shorter and shorter as seasons change from summer to fall to winter, according to Sciencemadesimple.com. As days get shorter there becomes less light available for photosynthesis to take place. Trees know this and will live off of stored food for the winter instead of wasting valuable energy producing leaves that will not benefit them. Leaves lose their green chlorophyll and as chlorophyll fades away we begin to see yellow and orange colors on leaves. These colors are always found in leaves, but are hidden by green chlorophyll during spring and summer.

Considerations

Water is an important part of photosynthesis for plants and trees.

Leaves carry out photosynthesis which provides trees with the energy they need to survive, according to Sciencemadesimple.com. Photosynthesis takes water that's absorbed through the roots, carbon dioxide from the air and sunlight to create glucose. Chlorophyll plays an important role in photosynthesis by helping leaves absorb sunlight. Chlorophyll has a green pigment which gives leaves their color.

Leaves of deciduous trees undergo many changes before they finally fall from a branch. The bottom of each leaf contains a layer of cells known as the abscission. This layer carries food and water to the leaf from the tree. As fall arrives this layer begins to swell and produce a cork like material that eventually cuts the leaf off entirely from the tree.

Function

Plants used stored glucose to survive during the winter.

During summer months leaves produce more energy than they need for growth, according to Sciencemadesimple.com. This extra energy, or glucose, is stored for winter months when most plants will shed their leaves.

Color

Orange colors come from a pigment known as carotene and yellows come from xanthophylls.

Leaves with red and purple color result from glucose that's left in leaves after photosynthesis stops. Bright red and purple colors also come from anthocyanin pigments. Cool nights combined with sunlight during the day turns this glucose into a reddish color. Oak trees have leaves with more of a brownish color that results from waste left in the leaves after photosynthesis stops. Orange colors come from carotene, yellows come from xanthophylls and browns come from tannin.

Types

Pine trees are evergreen trees that keep their leaves throughout the entire winter.

The main three types of plants are annuals, perennials and evergreens, according to Sciencemadesimple.com. Annuals live during the spring and summer and die when the winter comes. However, their seeds stay in the soil after they die and grow into new plants the following spring. Each year new plants grow from seeds, which is why these plants are called annuals.

Perennials such as trees and shrubs usually live for more than two years. When winter arrives the leaves and stems of the plant die, but the woody parts survive the winter. Perennials survive off stored food during the winter since they cannot carry out photosynthesis.

Evergreens maintain the majority of their leaves during the winter regardless of reduced sunlight. Leaves of evergreens are resistant to cold and moisture loss. Examples of evergreen trees include pine and fir trees.

Misconceptions

Trees lose their leaves on purpose to save energy during the winter when less sun is available.

Trees lose their leaves on purpose because of the lack of sunlight that exists in the winter. It would take a tree more energy to maintain a leaf than the amount of energy a leaf would provide a tree during winter.

References

• Science Made Simple: Autumn Leaf Color
• Awesome Autumn by Tooter 4 Kids: Why Do Leaves Change Color?
• USDA Forest Service: Why Leaves Change Color
• Farmers Almanac: What Causes Leaves To Change Color?
• Home Cook'n: Why Do Leaves Change Color in the Fall?