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Capillary Action of Water in Plants

Capillary Action of Water in Plants

In this science project, you will use food dyes to follow the path of water through a carnation. All plants, even those living in deserts, need water to survive. Plants use water to keep their roots, stems, leaves, and flowers healthy and to prevent them from drying out and wilting. The water is also used to carry dissolved nutrients throughout the plant.
Most of the time, plants get their water from the ground. This means that the plant has to transport the water from its roots up throughout the rest of the plant. How does it do this? Water moves through the plant by means of capillary action. Capillary action occurs when the forces binding a liquid together (cohesion and surface tension) and the forces attracting that bound liquid to another surface (adhesion) are greater than the force of gravity.

A simple way of observing this is to take a teaspoon of water and gently pour it in a pool on a countertop. You’ll notice that the water stays together in the pool, rather than flattening out across the countertop. This happens because of cohesion and surface tension. Cohesion is the attractive force that pulls similar substances together. In this case, the individual water droplets are being pulled together. The force of the pull is strongest at the edge of the pool. The water droplets at the edge have fewer neighboring water droplets, so they cling more tightly to those around them; this is known as surface tension. Now gently dip the corner of a paper towel in the pool of water. The water is attracted to the paper and “climbs” up the paper towel-this is capillary action.

Materials and Equipment

For this science project, you will need to gather the following items:

Water (1/2 C.)


Measuring cup

Glass or plastic cup

Blue or red food dye


Several white carnations (minimum of 3)

Knife (ask an adult for help with the knife)

Camera (optional)

Experimental Procedure

Measure out 1/2 cup of water.

Pour the water into a glass.

Add 20 drops of food dye to the water in the glass. Stir with a spoon until the dye has fully dissolved in the water.

With the help of an adult, use a knife to cut the stems of several (at least three) white carnations at a 45° angle. Be sure not to use scissors, as they will crush the stems, reducing their ability to absorb the water. Place the carnations in the colored water.


Here are some additional questions you can investigate with this science project.

Do you see the same results with other flowers and plants? How about trying another white flower, like a daisy? Or try a plant that is mostly stem, like a stalk of celery.

What are the results if you use other colors of food dyes? Is the effect easier or harder to see?

What happens if you increase or decrease the concentration of food dye in the water? Try using one-half, twice, four times, and ten times as much food dye.

How would you make a multi-colored carnation? Hint: Two methods to try are:

Leaving the flower for a day in one color of water and then putting it in another color of water for a second day

Splitting the stem in two and putting each half of the stem in a different color of water.

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