Color-Changing Process in Deciduous Leaves (page 2)
Light is necessary for a plant to produce chlorophyll. During the natural aging process of plants, chlorophyll molecules break down and are replaced. But without light, when the chlorophyll breaks down, it is not replaced. When the chlorophyll is no longer present, other pigments in the leaf that were masked by the color of chlorophyll can now be seen. In this experiment, the paper strip blocked the sunlight, and in time, the chlorophyll present in the leaf broke down and the yellow pigment it masked became visible. The fact that the part of the leaves under the holes covered with transparent (allows light to pass through) tape did not turn yellow shows that covering the leaf did not cause the color change.
This same color-changing process occurs in deciduous leaves in the autumn when they no longer produce new chlorophyll. The yellow and orange pigments in the leaves do not break down as fast as chlorophyll does, so they are seen only when the green chlorophyll is gone.
More Fun With Leaves!
A leaf's yellow color pigments are masked by the presence of green chlorophyll. Try this activity to make leaf art by covering and then uncovering pigments. Draw a leaf shape on a piece of white copy paper. Use a yellow marker to color the leaf. Using a dark green crayon, color over the yellow with a thick layer of green. Open one end of a paper clip and use the tip of the paper clip to draw designs in the colored leaf. Press down on the clip only hard enough so that it scratches away the green layer and exposes the yellow marker layer beneath.
- Burton, Jane, and Kid Tailor. The Nature and Science of Leaves. Milwaukee: Gareth Stevens Publishing, 1997. Information about leaves, including how they change color.
- Johnson, Sylvia. How Leaves Change. Minneapolis: Lerner Publications Company, 1986. Information about deciduous leaves, including how they change colors.
- VanCleave, Janice. Plants. New York: Wiley, 1997. Experiments about plants, including some about color changes in leaves. Each chapter contains ideas that can be turned into award winning science fair projects
Warning is hereby given that not all Project Ideas are appropriate for all individuals or in all circumstances. Implementation of any Science Project Idea should be undertaken only in appropriate settings and with appropriate parental or other supervision. Reading and following the safety precautions of all materials used in a project is the sole responsibility of each individual. For further information, consult your state’s handbook of Science Safety.