We did an experiment a while back to study the capillary veins in flowers. I liked that a lot, but the problem was that the stem of the flower was so small, we could not observe the veins directly. We could just observe the end result. So I decided to try again, but this time using celery as the veins are larger in that and it is easy to get this time of year. So I bought some celery and used the same colouring stuff as last time (food colouring in red and blue).
For this experiment you need:
- at least two stems of celery
- two glasses (one is sufficient, if you only want to use blue colour)
- food colouring (blue and red are used here)
- about 5 minutes prep and patience to wait for the results
This experiment is very easy to do. To prepare for it, get the celery, the same amount of glasses as you have colours you want to use, the colours and some water. Pour the water in the glasses. Add the food colouring. My daughter added the colours, so we used a liberal amount of each. Then add the celery sticks and leave to wait.
You can see the change of colour quite soon. Next day it is already quite evident. It is easiest to see with blue colour. Previously I thought that the red did not rise, but in fact it did even in the flower-experiment. It is just harder to see. So I recommend using blue. Once the colours were sufficient evident, we (well, I) cut up the celery stems to show how the colour had risen (see picture above). It was quite difficult to cut the length of a capillary vein, but luckily I had a few stems to try with. As I did the cutting and we did the studying of the colours throughout the celery, we discussed why this happens.
Plants use the capillary veins to bring water from the roots to the leaves. This works in flowers and in trees the same way. As water is vaporised in the leaf, more water gets pulled up to replace the vaporised water (for more info and experiments on water, study the experiments on liquids here). The colour travels with the water, but gets left behind as it does not evaporate with the water. So the leaves turn blue (or yellow as is the case when using red).
If you have questions about these experiments or instructions, leave me a comment and I will answer and improve these instructions. Also, please remember like and share if you find this useful.
Copyright text and images: Satu Korhonen. You are free to try these experiments out, use them in your teaching. But instead of copying the text or images, link back to this page.