Seeking Sunlight!
Grow a plant through a maze and learn how and why plants grow towards sunlight
What you need:
- A responsible person to help you if you need help or supervision with cutting!
- A cardboard box — a strong delivery box is ideal; the one we used was 50cm tall and 28 cm wide
- Extra cardboard (from a box or your recycling)
- A few bean or pea seeds
- A small quantity of compost or soil
- A few sheets of kitchen roll
- Sharp scissors or a craft knife
- Sticky tape or glue
- One or more plant containers — e.g. yogurt pots or part of a squash bottle
- Water
- Optional — large elastic band or string
- Optional — paints or pens
- Optional — camera or camera phone
Be careful of:
- Cut the carboard carefully! Be aware of sharp scissors or knife, and even the edge of the cut card!
- Wash your hands after handling soil or compost.
Instructions:
- First, you need to prepare your plant maze — use the photos to help. The box needs to be upright, and the front needs to open and close. Tape up any other open sides to make sure it is strong, and no light is getting in.
- Cut a large hole in the top surface of the box (as shown in photo). This is quite tricky, so make sure you do this bit safely!
- Tape or glue 2 or 3 pieces of card horizontally across the inside of the box, making sure they do not go all the way across (see photo). Use your spare carboard for this.
- Double check that when the front of the box is closed, the only light is from the hole in the top. You may need to use tape, string or an elastic band to make sure it closes well.
- Now, you need to prepare your seeds. You can use one or more plant container, depending on the size of your box and how many seeds you have. Each container needs a small amount of soil or compost in the bottom. A sheet of kitchen roll rolled inside the container can be used to help see the seed as it starts to grow. Add a few seeds around the edges of each pot and water them.
- Optional: decorate your box. You could paint it like a jungle, or label and paint it in bright colours to make sure everyone knows it’s your scientific experiment and must not be moved!
- Place the box somewhere safe and light and out of the rain. Put the pots inside the box and close the doors carefully.
- Check the seed pots each day and water them if the soil feels dry. Make sure you close the box back up carefully straight away!
- Your seeds shall take a few days to germinate (start to grow). You might want to take photos as they do.
The science:
- The only light getting to your pea or bean plants is through the hole you made in the top of the box.
- Plants need sunlight to live — it provides the energy for something called ‘photosynthesis’ to take place. Photosynthesis is when plants take carbon dioxide from the air and water from the soil and use these in a chemical reaction to produce glucose and oxygen.
- You may already have heard of something called ‘hormones’. People have hormones, animals have hormones, and plants have them as well — although not exactly the same ones! Hormones are special messenger chemicals. They move through the plant or animal and control how target cells work. Target cells are different for each type of hormone.
- The plant hormone that makes your plants grow towards the light and around the obstacles is called auxin. Auxin makes plants cells in the plant stem grow by division (splitting) and elongation (makes them longer).
- Auxin is more concentrated (there is more of it) in the shaded side of the stem. The shaded part of the stem, furthest under the card obstacle in your maze, grows faster that the side of the stem with more light.
- This means that the plant can change the direction of its growth, so that it always grows towards the direction of the light that it needs!
Investigation Ideas:
- Change the seeds you grow — try pea and bean seeds, sweet pea seeds, or others.
- Try different mazes — change the size or the number of obstacles.
- Grow a few of the same seed you used in your box maze in a separate pot, to find out how they would usually grow, without obstacles.
- Have a look around your garden or when you go out for a walk for plants that have grown towards sunlight.
The challenge:
Can you grow a plant that makes it all the way through your maze? Post a picture!
