The kids and I are really enjoying gardening at the moment, watching our seedlings grow and planting out more seeds. As we watch them grow it also gives us a great opportunity to explore plants more and look a bit more at the science of them. In the past we’ve looked at how plants drink through colouring flowers and I’ve explained to the kids this is due to transpiration and that the water with the food colouring is transported up through the stem however it’s not been easy to see the actual vessels involved. I them remembered a very simple classic science experiment that I had done in my classroom many times with celery and I set about setting it up with the kids.
Materials needed for the Celery Science Experiment
Celery with leaves still on
Liquid Food Colouring
Glass or glass Jar
Setting up the Celery Science experiment
In a glass add water and add a few drops of food colouring – it’s better if it is the none natural sort as the natural food colouring which is cloudy the particles of colour are too big to be transported up the stem of the celery and it won’t work.
Mix well and add in the celery
Leave in a window sill and watch the colours appear on the leaf.
Once the experiment is over and you can see the colours in the vessels of the stem by cutting across the celery – there will be circles which will be the colour of the food colouring.
Yes this is a cool science experiment and the kids loved seeing the colour appear in the leaves, but there is some real science behind it. The experiment shows a process in plants called transpiration – it’s the transportation of water through the plant, nutrients that the plant needs are dissolved in the water and taken to the parts of the plant that need them. Because the food colouring is small particles they can be transported in the water as well and you can see the progress.
The leaves of the plants have small holes on them that are connected to the vessels in the plants – the holes allow water to evaporate out and that forms a suction pressure in the vessels drawing water up through the roots. The holes on the leave are called Stomata, the vessels that bring the water up through the stem the Xylem and the roots draw the water from the soil.