IProposeWe: make color changing carnations

Materials

• 6 white carnations
• 6 plastic cups
• Food coloring (red, yellow, blue and green)
• Knife
  
• Water

Procedure

1. fill each cup half full with water.
2. add about 20-30 drops of food coloring to each cup of water. In this case, more food coloring is better!
   
3. before placing any of the flowers in the colored water, have a adult trim the stem of each flower at an angle to create a fresh cut. for cut flowers, it is important for the stem tubes to be filled with water.
   
4. place one freshly cut white carnation in each of the cups of colored water. save the remaining two carnations for the next step.
   
5. use a sharp knife to slit the stem straight down the middle. put each half of the stem into a cup of different colored water (try positioning the red and blue cups next to each other, for example). then see which color will soak up.
   
6. you'll want to check back every few hours to see how things are progressing. it may take as much as 24 hours for the colored water to work its way up to the white petals. At the conclusion of your experiment, examine everything (leaves, stem, etc.) to see where the trace of the color comes from.

Hint:

• cut the stems under water so no air bubbles can get in to break the tube of water and make the flower wilt.

Safety Procedure and Remember To's

• have adult help to cut the stems of the carnations and anything else involving the knife.
  
• keep the stem tubes filled with water, because if air gets in the tube, no water can travel up to stem.
• remember to record all data to help find the source of the colors.
• notice mixing colors and the amount of time needed for the colors to travel up.
  

Scientific Principle

• when a flower is cut, it no longer has it's roots, but the stem of the flower still "drinks" up the water and provides it to the leaves and flowers.
• water evaporating from the leaves, buds and petals (TRANSPIRATION) pulls water up the stem of the plant.
• the water can evaporate because water is very sticky--to itself (called water COHESION) and because the tubes in the plant stem are very small (in a part of the plant called the XYLEM). This process is called CAPILLARY ACTION.
• some chemicals and pollutants, just like the color dyes, may travel up into the plant and affect its health or growth.
• the blue dye will go up the stem the fastest!

Links
history and meanings of carnations
transpiration-cohesion-tension theory