How to... Make amazing changing colour plants!

In this experiment you can see how plants transport water all the way up their stems to their leaves and flowers. Water helps a plant to transport nutrients around it, and helps support the plant standing up (plants go floppy if they don’t get enough water!) Water is taken in through the bottom of the plant, but how does it get all the way to the top?!?

Always remember to ask your parent or guardian to help you.

What you'll need:

A large beaker, mug or vase Water Food colouring - red or blue works well A pair of scissors Some plants - pick some of the following... - Celery sticks with the leaves still on - White flowers - Lettuce or other green leafed plants

Step 1: Prepare your plants!  Make sure you get an adult to help you with this part.  Using scissors, cut off at least 2 cm from the bottom of each of the stems of the plants you have selected. Then pour some water into your container and add at least 5 drops of food colouring, so that the water becomes dark with the colouring.

Step 2: Water your plants!  Once you have done this, place the plants that you cut into the container with coloured water

Step 3: Wait and Watch...  Now leave your plants somewhere sunny - maybe on the windowsill. Check your plants after a few hours - what do you notice happening to them?  How do you know the water has reached the top of the plant? Leave your plants overnight in the water - what do you notice about the colour after a longer period?

What should happen?

You should see that as you leave the plants in the water, the plant gradually turns more of the colour that you added into the water. If you used white flowers, you will see the flowers change colour, and if you used celery stick or another leaf plant, you will see their leaves change colour too!

Why does this happen?

Water travels up the stem of a plant through long thin tubes called Xylem. Water moves up these tubes through a process called Capillary Action. Molecules of water are attracted to molecules that make up the tube. Water molecules at the top are pulled up, and they attract the water molecules underneath them, and so pull them up the tube too!

A sponge also absorbs water by capillary action. All the gaps in a sponge act like thin tubes that pull in the water molecules around.

Find out more…

If you used a celery stick, once you have left it for long enough to absorb the water and food colouring, cut another centimetre or two from the bottom of the stick. What do you see?

If you look very closely you should see some small circles at the bottom of the celery stick that are the same colour as the food colouring you used. These are the Xylem (the tubes that carry the water up the plant).