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Let’s Talk Science and the Royal Society of Canada have partnered to provide Globe and Mail readers with relevant coverage about issues that affect us all – from education to the impact of leading-edge scientific discoveries. Let’s Talk Science offers a number of fun activities to get youth engaged in STEM. These hands-on activities encourage active learning and discovery using materials commonly found at home.
Just like animals and humans, plants need water to survive. Plants get the water they need from their roots. Root systems are designed to go deep into the soil and absorb water and nutrients.
Experiment with celery to learn about the structures that help plants take up water.
What You Need
● Celery Stalk
● Clear cup
● Water
● Food Colouring (Blue, red and purple work well)
What to Do
*Safety first! Cut the celery for young children and always use caution when sharp knives.
● Cut a long stalk off of a head of celery.
● Fill a clear cup 3/4 full of water.
● Add 10 drops of food colouring to the water.
● Place the celery stalk in the cup. What do you think the celery will look like tomorrow? What about the water in the cup?
● Put the cup in a safe place overnight and observe the following day. Does the celery look the same or different? What do you think has happened?
What’s happening?
Roots bring water into the plant and xylem (tiny tubes) carries the water to the rest of the plant. Xylem is a system of hollow tubes that act like straws in a plant. It allows the plant to draw water up its stalk or stem. Sometimes celery has “strings,” which are several xylem tubes grouped together. Did you know that a celery stalk is not a stem? It is actually the part of the leaf called the leaf stalk. This is why we call the part of the celery that we eat the stalk.
When water gets to the leaves at the top of the plant, it evaporates through tiny holes in the leaves in a process known as transpiration. Transpiration results in the evaporation of the water at the top of the xylem. More water is then pulled from the roots to keep the xylem full.
Why does it matter?
Xylem not only helps plants by providing them with the water they need, xylem also helps to provide structural support for the plant. The rings you can see in a cross-section of a tree’s trunk are actually old xylem. They make wood hard enough to be used as a building material.
Investigate further
● Observe the progress of the water in the celery stalk. Check it by peeling away part of the stalk after 1 hour, 2 hours, 4 hours, etc. What is the depth of colour at different times? Does the water move faster or slower than you expected?
● Try this experiment again. This time, put one celery stalk (in water and food colouring) in a well-lit place and another celery stalk (in water and food colouring) in a dark place. Is there any difference in what happens to the colouring? What could explain this?
● Try other colours of food colouring. Which colours can you see the most clearly in the celery stalk?
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