Stem senses
experiments!
Below you can find two experiments to try at home or in the classroom. Feel free to download them for easier use.
experiment: Hearing
Music to grow up to
Aim
This experiment aims to explore whether plants will grow better when they are exposed to music, compared to plants which are not exposed to music.
Materials
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2 x container with lid (large enough to place 2 pots inside of each)
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4 x packets of water cress seeds
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4 x pots
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Soil
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Water
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Music playing device
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Pen
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Label
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Ruler
Method
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Plant your water cress seeds into the 4 pots, and then split the 4 pots between the 2 containers, placing 2 in each;
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Water regularly and allow them to grow until you can see them begin to poke out of the soil;
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Take a photo of cress seeds and measure their initial growth using the ruler;
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Once you can see them poke out of the soil take one jar and label it as "exposed to music" ;
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Once a day for an hour place the music playing device inside of the "exposed to music" jar with the water cress;
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Play a chosen genre (classical is recommended) for the whole hour;
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Ensure that the other container is placed well away, or that the lid has been firmly placed on, as this container will not be exposed to any music;
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Continue this once a day for a week;
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At the end of the week take a photo of the cress seeds from both the exposed and non exposed jars. In addition, measure its growth from the top of the soil to the top of the cress;
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Compare the photos and measurements from the beginning of the week and those at the end of the week.
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What differences in growth are there between the exposed and non exposed water cress plants?
What you should expect to see...
There is much scientific debate on whether plants truly grow better when exposed to music, with some botanists even branding this area of research as a pseudo-science. One of the earliest studies to suggest that plants may grow better when exposed to music was conducted by Dr Singh in 1962 at Animalia university. He exposed plants to classical music, finding a 20% increase in the growth rate of plants which were exposed to music compared to those not exposed to music. The Researcher Dorothy Retallak even experimented with different kinds of music, finding that plants exhibited poor growth when exposed to heavier genres of music such as rock. Therefore, based on previous experiments, you may see the plants which have been exposed to music as having grown more than the plants not exposed to music.
Why?
Despite scientific scepticism some interesting theories have been placed to these findings. Most notably a 2014 study looking at the effect of different soundwaves on plant growth, suggested that certain vibrations could increase the division and growth of plant cells. Other effects included increased membrane fluidity, allowing for increased protein and lipid diffusion, as well increased hormone and enzyme activity. All of these are factors which have yet to be formally tested.
Back to hearing page
experiment: Sight
A plants favourite colour
Aim
This experiment aims to show you how different wavelengths of light affect plant growth.
Materials
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Cardboard box
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4 x packets of water cress seeds
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4 x pots
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Soil
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Red, green, blue and clear cellophane
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Cellotape
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Scissors
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Lamp
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Water
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Box cutter knife
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Ruler
Method
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Start by growing one set of your water cress seeds. Plant your water cress seeds into a pot, water regularly and allow them to grow until you can see them begin to poke out of the soil;
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As they grow make a circular hole about 3cm in diameter in the middle on one side of the cardboard box;
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Place one of the coloured cellophane sheets over the hole you have just made in the cardboard box;
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Take a photo of the pot of water cress from the side and then place it into the cardboard box;
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Place a lamp over the box, so that it is shining onto the cellophane sheet. The cellophane will change the colour of light the plant recieves;
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Turn the lamp on during the day and off at night and allow the cress to grow for a week;
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After a week remove the cress from the box and take a photo of its growth. In addition, measure its growth from the top of the soil to the top of the cress;
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Repeat this experiment with all 4 colours of cellophane;
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Compare the levels of growth for the watercress placed under different coloured light. Which light did the cress grow most successfully in?
What you should expect to see...
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Seedlings which are grown under the clear cellophane will grow the best
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Seedlings exposed to only one wavelength of light will not grow as well as those grown under the clear cellophane
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Of those seedlings grown under one wavelength of light, seedlings will grow best when exposed to the blue and red light.
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Seedlings grown under green light are likely to show the smallest amount of growth.
Why?
The seedlings grown under the clear cellophane will grow the best because they are exposed to the full spectrum of light. Under these conditions plants can absorb a range of wavelengths of light, each of which has a different use for plant growth. Seedlings exposed to only one wavelength of light are limited in what they can absorb. The plants exposed to only one wavelength of light will grow best under red and blue light compared to green light. Red and blue light have been shown to increase the efficiency of photosynthesis, which is the key mechanism for plant growth. Greenlight is mostly reflected by plants therefore it is not as useful to plants as other wavelengths of light.
Did you get the results you expected?
If not, think about how you could redo the experiment differently so that you can replicate the above results.
This experiment was simplified from The plant phototropism experiment, click here to go to the original experiment.