Q:

Why do leaves turn brown in autumn?

A:

Leaves turn brown in autumn due to the deterioration of chlorophyll, the green pigment found in all leaves responsible for absorbing light for photosynthesis, explains the U.S. Forest Service. Intrinsically, the trees are aware that approaching winter weather will not offer enough sunlight or water to sustain their leaves, so the leaves fall off and the trees go dormant.

When tree leaves turn brown and fall off, the tree is in the process of suspending its functions for the winter. When autumn sets in, the days grow shorter and the amount of sunlight the trees receive is diminished. Additionally, due to a lack of rain in the winter months, drought has an effect on a tree being able to sustain its leaves. This combination of lack of sunlight and water leads to the halt of vein activity within the leaves. Ordinarily, these veins are responsible for pumping nutrients throughout the tree. When there are no nutrients to pump, the veins shut down. When this occurs, the leaf eventually dies and falls from the tree. Brown leaves are seen closer to winter and follow the warm foliage of autumn. When they litter the ground at the base of the trees, they act as an all-natural fertilizer. When spring comes back around, those leaves decay, replenish the tree and aid in leaf regrowth.

Learn More
Sources:

Related Questions

  • Q:

    What happens in the light independent reactions of photosynthesis?

    A:

    The light independent reactions of photosynthesis, known as the dark reactions, use ATP and NADPH generated during the light reactions to synthesize sugar precursors. In the most common scenario, called the Calvin Cycle, carbon dioxide is incorporated into a stable three-carbon compound called phosphoglycerate (PGAL), which serves as the precursor of glucose and other sugars. Six turns of the Calvin Cycle generate the equivalent of one glucose molecule.

    Full Answer >
    Filed Under:
  • Q:

    What does chlorophyll mean?

    A:

    Chlorophyll is a green pigment found in plants and cyanobacteria, which are bacterial organisms that make their own food. This pigment absorbs light energy for use in photosynthesis.

    Full Answer >
    Filed Under:
  • Q:

    What is photosynthesis?

    A:

    Photosynthesis is the process by which green plants manufacture their own food. The process takes place in small structures within the plant’s cells called chloroplasts. Photosynthesis evolved about 3 billion years ago, yet it remains the most important method for harvesting the sun’s energy on the planet.

    Full Answer >
    Filed Under:
  • Q:

    Is photosynthesis endergonic or exergonic?

    A:

    Photosynthesis is an endergonic reaction. An endergonic reaction requires or absorbs energy from its surroundings, while an exergonic reaction releases energy. Most reactions that create or synthesize compounds are endergonic.

    Full Answer >
    Filed Under:

Explore