(This activity is most appropriate for children 12+ and may require parental guidance)
Most people understand that all plants need consistent light and water to survive. However, it is common for many of us to dismiss plants as inanimate objects that we see in places we haven’t yet paved over. The ways that plants utilize light and water can be fun to experiment with, and they can give us a better understanding of that fact that plants are living beings that can sense and respond to their environments.
Colouring Cut Flowers & Playing with Phototropism Experiments: Key words and concepts that should be kept in mind:
These experiments will take time and patience, but should get you some interesting results that will spark discussion with your kids (and if you're a teacher, your students).
How water is transported through plants:
When a plant is rooted in soil, it absorbs water into itself through its roots. The roots of a plant act as natural filters that take in only what would benefit the plant and leave unnecessary minerals and substances in the soil. It is then transported up through the plant through capillary action, which is basically the plant drawing water up through its body like a straw by utilizing the natural properties of water and its own mechanisms. The water helps keep the plant firm, get nutrients to all its cells, and aid in photosynthesis.
How the colour changing flower experiment works:
By cutting the plant at the stem, we remove its natural filter in the roots, which would otherwise have stopped the food colouring from getting into the plant. The water is then drawn up through the same process of capillary action, and because the water we use is coloured, the plant’s very cells become coloured in the same way. It shows best in white flowers because they have no natural colouring; it is harder to see in green leaves and stems.
Phototropism is the scientific word for plants naturally orienting themselves towards light. I find that it makes sense at an intuitive level that plants would look for the light automatically, but I still find it fascinating to see just how much plants can really bend themselves to get themselves closer to light sources, and I think students will as well.