Science Buddies: "Ask an Expert"

Hi There,
We are working on a project attempting to change the color of flowers. We used the guidelines in the Suck it up: Capillary action of water in plants.
After 72 hours the outside edges of the petals turned color. I am wondering if this is the expected outcome, I thought the petals would all change color not just the outer edges. Also, if the color is supposed to show the movement of water through the flower why does the whole petal not change color. I also noticed that when a flower dries out the outer edges of the flower seem to dry out first, the same area where the color appears on the petals of the flower is there any relationship to this. I am also trying the experiment of using twice and doulel the amount of food dye which appears to be following the same pattern as the original experiment.
Jill

Hi Jill,

Sounds like a fun project to see capillary action!

So, why did just the outer edges change color? Why not all the petals?
There may be a couple of reasons for this. Think of the flower as a straw from the bottom of the stem to the tip of the petals. Using capillary action, the plant keeps drinking up the dyed water until it's brought up all the way to the tip of the petals just like when we drink through a straw. Now, if the flower can still drink the water up or if there is enough dye, it should be able to transform the entire flower into the color of the dye. If the flower couldn't drink up the water after 72 hours, you can help it.

Because the flower no longer has a root system, the stem needs to be kept well-maintained and fresh to keep being able to drink up the water. You'll need to have an adult help you cut the tip off a little bit at an angle every other day to help the stem "drink" up the dyed water, use cool water, and change the water every day or every other day to keep it drawing up the dye. It could also be that the concentration of the dye is too little at the original or two times the amount--what happens if you try 4 times or 8 times? The dye doesn't damage the flower, so try it and see


The outer edges dry out first?
Just as humans can become dehydrated through sweating, flower petals will dry out from transpiration if they do not have a source of fresh water. Petals are covered with minuscule openings called stomata through which water evaporates, so the lost water needs to be replaced for the plant to stay healthy. Flower stems draw water up from the roots to the petals through a series of channels, or tubes, named the xylem. Cut flowers placed in water continue to draw water up through the xylem to keep the leaves and flower petals well hydrated. As water droplets leave the stomata, they are replenished.

Remember the straw concept? Well, it kind of works the opposite way too. You'll see this happen too during the fall season when trees suck back their chlorophyll into their roots and trunk to store it for the winter--which is why tree leaves change colors and eventually brown and fall off. It's the same thing for flowers. In the case of a cut flower instead of a planted one, when it starts to wilt, it draws water from the tip and back down to the stem to keep the flower's stem moist.

Here is a great website from the Missouri Botanical Garden to help you learn more about plants: http://www.mbgnet.net/bioplants/parts.html
You can find a good explanation about capillary action here: http://www.uni.edu/~iowawet/H2OProperties.html

Hope this helps! Good luck with your project

Hi There,

I have a follow up question now that I have compledted the experiment. I am unsure exactly what is considered the Independent varialble, the dependent variable and the control variable. I have three carnations, in dyed water (20 drops of food dye) measured over time interval.
This is what I am thinking:
Dependent variable: Color change observed in flower
Controlled variables: All three carnations in same dilution of water/dye (i.e. 20 drops dye ot 1/2c water) I put all the carntions in the same container
Independet variable: Time, Measured in hours.
I am thinking I have my Dependent and independent variables reversed.
Also on my poster board I was planning on using a table showing observations noted at the time intervals and a time line with the time intervals as identified in the table and corresponding pictures of the flowers taken at the time intervals. I thought a time line might be more appropriate as I don't think I can use a graph since I am making observations which are subjective.
Please let me know if I am on the right track.
Thanks
Jill

Jill,

You have the correct variables--good job!

A timeline is a sort of graph, and I think what you propose would be fine. However, I would speak to your teacher to make sure that they are also okay with it and that it satisfies any requirements they may have for figures/graphs just to be sure.

Very Interesting Project!

Some other controlled variables that you could add would be the same lighting, the type of water and the same type of dye.

Great idea.I have experienced color change with more than one type of plant.