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Polka-Dot Celery Teacher Sheet

Polka-Dot Celery Teacher Sheet

Introduction

This teacher sheet will provide some background information on the experiment along with the answers to the pre- and post-lab questions the students will receive. 


Background Information

The Polka-Dot Celery experiment introduces students to the vascular system of a plant. Keep in mind some of this basic information is already in the Amazing (Mostly) Edible Science book, so you can have them read it first and then discuss as a class. Start off with explaining the two main parts of the plants, which are your shoots or stem and the roots and what roles each play. Students should hopefully understand that the roots will absorb water from the ground up into the stem and that photosynthesis, which makes sugar for the plants, will occur at the leaves and the plant will transport the sugars down into the roots. The vascular system, or veins of the plant, works to transport water and sugar. The students are asked to explain in their own words how they think the water is being sucked up through the veins of the plant. The basic chemistry here is that water sticks to itself (cohesion) and to the vein walls (adhesion) and goes against gravity to be pulled up through the plant. This suction is due to water transpiring out of the top of the plant and diffusion pulls the water upwards. Diffusion is when molecules move along their concentration gradient going from a high to low concentration. In addition to thinking about how all this occurs, students are asked to come up with an experimental design to compare the suction of the celery stalks in different colored food dyes. Let the students have fun with this and make predictions about which color they think will be suctioned the fastest and how they would measure this. Have the students set up at least five conditions (blue, red, green, yellow, and tap water) to compare. It’ll be up to you if you want them to mix the dyes to come up with another color.

Pre-lab Questions with Answers

Draw a picture of a plant below and label which part is the stem and which are the roots. Which part of the celery are you using in this experiment?
The part of the celery being used is the stem.

What is the vascular system of the plant? Add to your picture above the direction water is being transported and the direction the sugar is.
The vascular system or the veins of the plant function to transport water and sugar throughout the plant. The water that is absorbed through the roots is transported upwards and the sugar that is made in the leaves is transported downwards.

Think of the suction of water up the plant stem like sucking water through a straw. How do you think this happens in plants?
Let students be creative here. They may come up with very interesting ideas! Then as a class you can discuss what is actually happening. As explained above, as water evaporates or transpires out of the top of the plant, it suctions the water up through the veins by the process of diffusion.

To compare the suction of the celery stems between different colors of food dyes, how would you set up this experiment? Draw out the experimental set-up below. Remember you want to be as consistent as possible between each condition.

How are you going to set up the experiment above and compare your results between conditions?

  • Add ___mL of water to each jar**
  • Cut the celery to ____ length**
  • Add ___number of drops of dye to each jar**

**As a class, you can come up with the exact measurements. To measure the results, we will measure the volume of the liquid each day or we will measure the height of the liquid using a ruler.

Do you think one food color will be suctioned faster than the others? Explain.
Let them be creative here with whatever they decide!

Observations

Discuss as a class the types of observations they will record to compare the celery between conditions. Emphasize the importance of making detailed observations about what the celery looks like compared to the tap water and also how the celery feels to the touch. They should record observations for all three days of the experiment.

Data Collection Table
It will be left to your discretion if you want the students to measure the volume of the liquid each day or measure the height of the liquid.

Condition (color of food dye)

Height or volume of water (cm or mL)

Day 1

Day 2

Day 3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Post-lab Questions with Answers

What are the “dots” on your celery stalks showing you?
The dots are the veins that have been colored by the dye

Using your observations and data collected, what conclusions can you make about the different colored food dyes?
This answer will depend on the experiment. Emphasize again that there is no right or wrong answer. They should trust their results and observations to make a conclusion. 

Name two other plants that you could substitute into this experiment.
They may come up with random ideas here, but any other stem vegetable or flower would be a good choice.

What were the possible sources of experimental error? What would you do differently if you had to set this experiment up again?
You may need to explain here what experimental error is. A way to explain this is to have them consider doing this experiment again the exact same way and ask them if they would get the exact same results. The answer will be no. This is due to experimental error and that is why in order to have more confidence in your results, experiments need to be performed multiple times. Some examples of experimental error could be the liquid evaporating out of the glass or the celery stalks not being identical. They also can be creative here in what they would do differently for the next experiment. They may come up with different colors, different plants, or maybe a different liquid.

This teacher sheet is a part of the Amazing (Mostly) Edible Science lesson.

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