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CHEN SCIENCE
T
I
K
COLOUR CHANGING CELERY
RECIPE
WHAT YOU WILL NEED
• CELERY
• A GLASS OF WATER WITH FOOD COLOURING IN
• SCISSORS
1. Use the scissors to cut a bit
off the end of the celery.
2. Put the celery in the glass
so that the bottom few
centimetres are below
the surface of the water.
3. Leave it for a few hours and
see what happens. The celery
should be the same colour as
the food colouring
Plants, like us, need to transport essential molecules for various processes. In plants, there are two
transport systems: the xylem and phloem. When you look at the bottom of celery, you can see tiny circles
- this is the xylem and phloem. The xylem transports water and soluble minerals and the phloem trans ports nutrients such as sucrose. The xylem is a series of tubes made up narrow and elongated cells,
different types of cells will make up these tubes.
Water is transported from the root to the leaves. It can be pulled up through the xylem when water is lost
through the leaves in a process called transpiration. This is because the stomata on the bottom of the
leaves are opened for gas exchange and water is lost in the process. This reduction in water causes it to
be pulled up through the xylem into the leaves, similar to how liquid is sucked up a straw. Only a small
fraction of water taken up through the roots is used for metabolic activities, such as photosynthesis, and
most is lost through transpiration.
Water can also be transported through the xylem due to root pressure. This is when the concentration of
water is lower in the root in comparison to the surrounding soil. This tends to be because of a higher
concentration of solute in the root. Water can be transported into the root through osmosis from a high
concentration to a low concentration of water.
When you put the celery in water, it will draw up the water through the xylem. The dye is taken up with it,
hence why the xylem will now be more easily seen.
How can you take it further?
• Leave it for longer to see what happens.
• Try flowers. They will take longer than celery – I left mine for around 12 hours – and using white
flowers will make the colour stand out. You can also try any other plant.
• Try different colours – is one colour more effective than the others?