How Do Carnations Absorb Colored Water?
Dyeing a white carnation by putting its cut stem in colored water--one of the most popular school science projects--relies on transpiration and capillary action to pull the colored water up through the stem to tint the flower.
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Fundamentals
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A cut carnation will draw colored water up through its stem to tint the flower. Most plants pull in water and the nutrients needed through their roots, drawing the water into the stem, leaves and flowers. Cut flowers no longer have roots but pull vase water to the leaves and flowers through the stem, according to Steve Spangler Science. When coloring is added to the vase water, it is drawn up into the plant and absorbed, tinting the flowers.
The process works especially well with white carnations and, sometimes, roses. Putting a celery stalk in colored water will change the color of the celery, usually within 24 hours.
Function
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Water is moved through the inside of a plant by evaporation on the outside, according to Steve Spangler Science. When water evaporates from leaves, buds and petals, the process called "transpiration" pulls more water up through the stem of the plant to replace the water that was lost. The movement of the water is called "capillary action." Once absorbed by the roots or a cut stem, water and everything it contains, including dyes, travel through the plant in tubes called xylem.
The process is much like when a person drinks a beverage through a straw, pulling the liquid from bottom to top.
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Alternatives
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Another way to see capillary action working is to dip the corner of a paper towel into a small pool of water and watch the water "climb" up the towel, according to Science Buddies. Sponges also work through capillary action, pulling water into all parts of the sponge.
Significance
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Plants need water to grow and produce their own food through a sunshine-powered process called photosynthesis, in which water drawn up into the plant and carbon dioxide pulled from the air combine, according to the National Science Teacher's Association. Through capillary action, water also transports nutrients to all parts of the plant and, by filling up cells, helps the plant stand upright, according to the association.
Experiments
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To experiment with capillary action in a carnation, cut the stem of a white carnation and place it in a vase or glass containing water dyed with a few drops of food coloring. The flower should gradually change from white to the color of the dye over a 24-hour period. Once the dye reaches the flowers, it usually can be tracked as it travels through the xylem or veins in the flower.
Some dyes move faster through a flower than others. To experiment with different colors, place individual cut carnations in separate glasses holding different colors of dyes and track the time it takes to change the flower's color. Another option is to carefully slice the carnation stem lengthwise from a few inches below the flower base to the bottom. Place each side of the sliced stem in glasses containing different-colored water and monitor to see which color tints the flower first.
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References
Resources
- Photo Credit carnation image by Christopher Hall from Fotolia.com colors of water image by weim from Fotolia.com
