Here is a very simple yet fun experiment. With the flu going through our house this was perfect!
First put some water in a glass. Put some food coloring in it. Preferably not green. We had some red left over from Christmas cookies. Take a couple of stalks and place in the water in some sunlight. (Try and choose stalks that have leaves.) Leave for approx 4 hrs.
The leaves are full of red inky water. Plants suck water up through the stem into the leaves. They need water to grow and keep healthy.
Cut a slice from the stem. Tiny red dots show the tubes that carry water up the stem.
Am I this creative? NO. You can find these simple experiments in the book "The Usborne Book of Science Activities..Volume Two.
I would have taken pics of the kids with the celery but they are in bed now. No worries..the experiment is not over.