This month’s simple science experiment will tinker with the inner workings of flowers and celery, too. Now we all know that plants don’t have a heart to pump their fluids up from the ground to their leaves, so how exactly does this happen?
The process at work here is “capillary action.” Plants have tiny little tubules going up their stems. Think about eating a piece of celery; those “strings” that get caught in your teeth are what I’m talking about. Water naturally attracts itself to these tubes through “adhesion” and gets pulled upward. The smaller a tube is the higher water will get pulled up. This is how even the mightiest trees bring water up from their roots to the tallest of their branches. How can we test this? I’m glad you asked.
A few white carnations or if you can’t get them, use a bunch of celery instead (the leafy kind), 2 vases or 2 tall drinking glasses, water, food coloring, and a sharp knife. Get your parents to help you with any cutting that needs to be done.
1. Fill 2 vases or drinking glasses with tap water. Add enough food coloring to each of them so the water is dark with it. Put different colors in each.
2. Carefully cut your white carnation down to about 18 inches. With a careful cut, slice the stem vertically from the bottom until just below the flower. If the cut is not even, don’t worry. The results are interesting. (If using celery, do the same cut, but don’t go quite as near the top, it may split).
3. Put the two ends of the carnation stem or celery into the two different glasses of water.
4. Water a few hours and make your observations.
5. If you didn’t already do the experiment with the celery, try it out. The effects are similar but not exactly the same.
You will notice that the food coloring makes its way up the stem and into the white flower petals, first coloring the edges and then making its way inward. Not only that, but the carnation is two different colors now, due to the water being brought up the tubes on different sides of the stem.
The food coloring gets pulled up along with the water through a process called “Diffusion.” This means that the food coloring wants to move from a place where there is a lot of it (in the glass), to a place where there is little (in the flower). The process is similar to when you spray air freshener in a room: the spray moves from where it started all throughout the room.
Let the carnations stay in the water for several days to get a good coloring. The celery is interesting, too, because when you take it out of the water, you can see the tubes completely saturated with the color apart from the rest of the plant material.
Do different colors work the same way? Would a red carnation turn purple if you dunked it in blue food coloring? What if you made purple food coloring with red and blue and then put the carnation in it? Do other flowers do the same thing? Ask your questions, and get them answered!
I hope you enjoyed this simple experiment and learned a little bit about how plants work. If you have more questions about this, or need tips about science fair ideas around this topic (or others), contact me with the info below.
Steve Davala is a middle school science and math teacher. He enjoys the hands-on approach to learning science, as do his two kids! Follow him on Twitter or ask him a science question at email@example.com.