🥔 Do potatoes sprout faster in the light or dark?

My hypothesis

If I change how much light the potato gets, then how long the longest sprout is on day 14 will ______, because ______.

🔊 You fill in the blanks. Think about why a potato has eyes at all, and what a sprout needs to do to reach daylight. A guess is a good because: the test finds out.

Change, measure, keep the same

Scientists call the thing you change the independent variable and the thing you measure the dependent variable. The things you keep the same are the controls: if one of them changed too, you wouldn't know which change made the difference. Try each of the 3 levels 3 times.

What you need

• 🥔 Potatoes: 9 small ones, the same kind
• 🍽️ Paper plates: 9
• 🛍️ A paper lunch bag: 1, big enough for three potatoes
• 🖍️ Crayons or markers
• 📏 A ruler

Steps

1. Choose nine small potatoes of one kind, each with its eyes just starting to bud.🔊
2. Set each potato on its own paper plate with the eyes facing up.🔊
3. Write windowsill, cupboard or bag on each plate, three of each.🔊
4. Put three on a sunny windowsill, three in a dark cupboard and three in a paper bag on a room shelf.🔊
5. Never water the potatoes, and look at them every two days.🔊
6. On day 14, measure the longest sprout on each potato in millimetres.🔊
7. Write each length in your table, and write down each sprout's colour and thickness.🔊
8. Draw a bar graph of the longest sprout for each place.🔊
9. Green skin and sprouts on a potato are not safe to eat, so never taste any of them.🔊
10. Wash your hands after touching the potatoes.🔊

Every step is one you can do yourself, with a grown-up nearby. Write each number down straight away, in the table below, so nothing is lost.

Your results table

From 4th grade, add the tries for each level and divide by how many there were: that's the mean, and it goes in the last column. Then draw a bar graph, one bar for each thing you tried.

Why it works

🔊 A potato is a plant's food store, packed so new shoots can grow from its eyes. A sprout in the dark stretches long and pale to search for light, while one in the light is usually shorter, sturdier and greener. Light also turns the skin green, and that green skin and the sprouts are not safe to eat.

Going further (7th and up): Change a second thing: keep red, white and yellow potatoes in the dark, and graph which kind grows the longest sprout.

Board layout

This project at your grade

From 4th grade up, the table gets a mean column. See every project for 2nd grade, or print a blank results table.

What a judge will ask

• What did you change, and what did you measure? I changed how much light the potato gets and measured how long the longest sprout is on day 14, in mm.
• What did you keep the same, and why does that matter? I kept the same kind of potato, about the same size and no water at all on any potato the same, so the only difference was how much light the potato gets.
• How many times did you test it? 3 times at each of my 3 levels.
• If you did it again, what would you change or test next? I'd keep red, white and yellow potatoes in the dark, and graph which kind grows the longest sprout.

Make it yours

Keep this project on this device and Peabody counts down to your fair day, with a plan for each day. Nothing is sent anywhere.

Try next

• 🌑 Does a bean grow taller in the dark?2nd–6th grade · 10 days of testing · about $2🌦️ Growing and weather · 🌱 Outside and plants
• 🌱 Do plants bend toward the window?1st–5th grade · 12 days of testing · free🌦️ Growing and weather · 🌱 Outside and plants